"You may be able to think of others besides these."
Maybe older siblings compete with younger siblings in various ways, and, *being older*, naturally win. e.g. maybe older siblings are much more successful at bullying younger siblings than vice-versa.
Social first-borns are a third parent to their younger siblings. First-borns are replaced as the cutest thing in the household. This is the effect; not more parental attention. They become parent-like and get attention for being helpful instead of cute.
- Firstborn siblings spend more of their early years exposed to and learning language from adults versus other children who are only slightly older.
- Similarly, firstborn siblings are more directly exposed to praise and expectations from their parents and other adults, vs the praise and social validation of another slightly older child. Thus they become more oriented to achievements that will impress adults, such as performance in school.
Are you sure that older siblings aren’t just more likely to try and please authority figures by performing thankless tasks like filling out user surveys ?
Maybe being older you get lots of opportunities to explain/teach things to a younger sibling, this makes you more reflective and self aware hence more likely to go into higher education get a PhD etc. The decline starting at 8 years might be because at 18 you move out and stop teaching your younger sibling things while they are still quite young and can be taught a lot of things, i.e, less than 13.
My personal hypothesis is that the greater uncertainty involved in raising a child for the first time leads to higher openness to new experiences. I'd guess this can go down a number of different paths in practice, but that cultures situated outside of the mainstream will be disproportionately firstborn as a result.
How do you know that "birth order" is not just a proxy for "age"? Maybe people who spent more formative years prior to smart phones are more receptive to long essays of the sort that you write.
- First borns are part of the "parental teaching structure" of subsequent kids.
- and also competitors, cooperators and imitators. I have a 9 yo and 6 yo and I can tell you they are both forever different, on questions of basic personality/desires because they have a sibling. There are things they do/love/hate because of how their sibling feels about them.
- is there any value to looking at school situations (such as Montessori) that often mix age groups? A class room of all 2nd graders is going to have different "social sibling" effects than one that's 1st, 2nd, 3rd all together.
- and what about the past, when almost all kids were raised more or less in a group - a swarm of cousins of varying ages? Being the first born in a house that only ever has 2 kids is one thing. Being the first born in a generation of cousins probably has different implications.
- did you ask any questions about pets (insert snark about "substitute kids") in the household?
You're only looking at 1/3 to 1/2 the picture. The interaction between the siblings, especially the role assumptions that go on.
Our children are 18 months apart. Just before our second was born, my wife took our daughter to the toy store so she could have a baby doll of her own, something that looked a lot like a real baby. Mom had the daughter give her baby doll a name (Baby Mike) ... OK ... with the thinking mom would have here baby, and our 18 month old daughter would have her own baby to mimic mom, instead of wanting to hold her baby sister.
Great idea, but wrong. Baby Mike went into the toy box to almost never return. Yes, she wanted to hold her baby sister, and we allowed this with close supervision, the older daughter was only 18 months after all.
But what happened was a total bonding, the younger grew up faster, as the protégé of the older, and the older did revert some especially when it came to diaper training. We had read about, and expected this.
I think there was growth and leadership developed in the older child, far vision thinking if you will ... which is pretty much what this forum is about.
The younger child didn't/ doesn't look to the horizon as much as she follows her older sister still in a lot of ways, they're 29 & 31 now.
And yes, I'm the elder of two, my sister is 16 months younger than I.
Whenever this topic comes up, I wonder how only children (no siblings) stack up against firstborns. What percentage of this blog’s readers are only children?
I’m also curious about how many female readers of this blog are only children vs male readers.
In my experience youngest siblings can instantly identify each other. They have been strongly socially conditioned; they were always the cutest, they were always smaller than their siblings, and parents had relaxed relative to the first kid. They're used to losing arguments and having things not go their way (being younger and smaller, not necessarily more or less on track), unless they work disproportionately hard for it.
Some anecdotes:
1. My parents *returned* the gameboy I was given as a birthday present, but my youngest sibling was allowed to have multiple consoles.
2. Although I'm three years older than my sister and she's three years older than our youngest sibling, we all learned to read within two years; I was late, she was on time, and the youngest felt left out and taught themself to read at the age of two. (Those early digital books that highlighted and spoke the word at the same work wonders!) Now, of the three of us, 1 and 3 are the most avid readers. (But 2 got a neuroscience degree, she didn't get off easy!)
3. My dad taught us all to program at the same time; we all started with the same level of competence and quickly developed our own styles. Of us, 1 and 3 are employed as software engineers now; 2 lost interest. (This was also part of a larger experiment on us; in the early 2000s there was a theory that girls didn't enter programming because they didn't have a cohort, which my dad found to be a testable hypothesis, so he not only taught us but also most of my sister's school class. It did briefly keep their interest as a communal activity, but it's not clear it had any long term effect.)
I (a first-born) have also surrounded myself with disproportionately first-born friends, I find we're on the same wavelength. But I know I'm pretty unusual, both in general and among first-borns, so I'm cautious about extrapolating my own experience in that regard.
An explanation of the birth-order effect diminishing with age gaps, which still makes the primary driver of the effect parental attention, could be that the first couple of years of a child's life are the ones that require the most parental attention. A second child who is two years younger than their older sibling will get less parental attention than a second child who is six years younger, because in the first situations, the parents are having to deal with a toddler.
I think I was in your "several biological siblings, no social siblings" group, because of the large gap between my older sisters and me (fourteen years). I've often thought I got the best of both worlds growing up. In terms of parental attention, it was like being an only child, but my parents were still experienced parents, and knew what they were doing because of my older sisters.
> One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower? If it’s about having quality time alone with Mom, someone with a sibling one year younger than themselves only got one year of quality time; someone with a sibling five years younger got five years. But it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one. Either the first year is very important, or I’m missing something.
The lived experience of parenthood makes it pretty obvious why small age gaps have larger effects. The mother of a newborn and a 1 year-old has less attention to devote to the newborn, because the 1 year-old is extremely needy. A mom who read dozens of books aloud daily to the firstborn 6 month-old probably reads zero to the second born at 6 months if there is also a toddler in the house. The newborn gets a lot more of Mom’s attention if the sibling is a 5 year-old able to feed herself, use the toilet herself, play without needing Mom for more than ten minutes at a time, etc.
My theory is that the average intelligence of the other family decreases for subsequent children. The first born interacts with two adults; the second born interacts with two adults and a child.
Hypothesis: "Firstborn" children are recuited as deputy parents when younger siblings come into the family.
I speculate: Consciously, or unconsciously, the oldest feels more like an adult from that point on, and may feel and behave more responsibly, and also may enjoy feeling more "accepted" by their parents into the world of adult society. Maybe younger children never feel this (although families where i.e. the oldest girl ends up with lots of maternal responsibilities are anecdotally common.) Maybe younger childen have a kind of extended childhood vs an "accellerated" childhood for first-borns.
On the same topic, research published ~5 years ago looked at athletic achievment by siblings in US professional sports. (link below...I think, it seems not to be showing up...) They found a HUGE positive effect for YOUNGER siblings, especially the second child in a family. (Note: this study had vastly more male children and brother-brother pairs, for obvious reasnos, but IIRC the effects were just as strong for the few female athletes in their study.)
Several reasons were posited, the two salient ones were:
-- Practice effects: The younger child is often playing with the older, and with other kids several years ahead, this is very tough competition and an intense learning environment.
-- Parental / Family experience: Parents learn how to navigate schools, leagues, coaching, sports-bureaucracies in general, and the younger kids get fast-tracked into the best opportunities.
For me, the absurd number that stood out was this: In US Baseball, 700 (!) pairs of brothers have played in MLB. The younger brothers, collectively, attempted 10x more stolen bases than the older.
Thomas Sowell talks about this in "Discrimination and Disparities". Here's what I highlighted in that chapter:
'A study of national merit scholarships, for example, found that, among finalists from five-child families, the first-born was the finalist more often than the other four siblings combined. First-borns were also a majority of the finalists in two-child, three-child, and four-child families. If there is not equality of outcomes among people born to the same parents and raised under the same roof, why should equality of outcomes be expected - or assumed - when conditions are not nearly so comparable?
Such results are a challenge to believers in either heredity or environment, as those terms are conventionally used.
IQ data from Britain, Germany and the United States showed that the average IQ of first-born children was higher than the average IQ of their later-born siblings. Moreover, the average IQ of second-born children as a group was higher than the average IQ of third-born children.
A similar pattern was found among young men given mental tests for military service in the Netherlands. The first-born averaged higher mental test scores than their siblings, and the other siblings likewise averaged higher scores than those born after them. Similar results were found in mental test results for Norwegians. The sample sizes in these studies ranged into the hundreds of thousands."
(...)
"Consider how many things are the same for children born to the same parents and raised under the same roof - race, the family gene pool, economic level, cultural values, educational opportunities, parents' educational and intellectual levels, as well as the family's relatives, neighbors and friends - and yet the difference in birth order along has made a demonstrable difference in outcomes.
Whatever the general advantages or disadvantages the children in a particular family may have, the only obvious advantage that applies only to the first-born, or to an only child, is the undivided attention of the parents during early childhood development. "
Dr. Sapolsky mentions this exact phenomenon in a lecture series on human behavioral biology. The data discounts fetal resource depletion and parental attention. He indicates that the current working hypothesis is that the firstborn is forced into a tutoring or mentorship role.
Hey, I'm one of those edge cases. I'm the oldest of two siblings, but my mother gave a child up for adoption 8 years before I was born. And I'm a classic older child, so one point for some sort of social vs. biological effect.
My guess would be that the difference is variance. Two populations with the same mean will be measured to have the same mean. This is often interpreted as no difference. However, if the standard deviations are different, the tails will look very different. In this situation, that would mean that first born have higher variance. Has anyone looked at the negative end of the spectrum? (As a reader, I’m obviously designating my end of the spectrum as the good side.) what’s the birth order like in prison populations?
>One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower? If it’s about having quality time alone with Mom, someone with a sibling one year younger than themselves only got one year of quality time; someone with a sibling five years younger got five years. But it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one. Either the first year is very important, or I’m missing something.
An older sibling one year older is always doing fresh things, and their one year younger sibling is always just redoing the thing that just happened- there is no novelty, less enthusiasm etc. With a greater age gap, the older sibling naturally ages out of intensive parenting at some point during the younger sibling's development and the younger sibling gets more attention, i.e. older sibling goes off to college when younger sibling is in 7th grade, younger sibling is now effectively an only sibling.
Making my first comment because I have actually thought a lot about this lately. Some anecdotal data to introduce my own theory.
My buddies from school are all very analytical, competent, and successful. Three stand out and they are all firstborn. They also stand out because their younger siblings struggled more and were more rebellious. Add to this general trend a half-exception: my brother and I.
I am a twin. Technically, I'm younger, but I have always been more academic and I was the first one to read, so I was the one who started with a natural advantage. My brother has indeed been "more interested in excelling in areas other than school, like trying to cultivate a special talent that the firstborn [or in this case younger twin] doesn't have." I still remember crying when I realized I wasn't as musical as him and he is now a composer, yet alas, not a frequent reader of ACX.
So here's my theory: older siblings start off with a natural advantage in intelligence. So similar to your second theory (in twins that advantage is decided more randomly because they are otherwise so "identical"). However, younger siblings don't immediately start to differentiate themselves. Instead they are PRESSURED to match the performance of their older siblings. Some of them just can't compete and rebel. They are then led away from traditional marks of success. So even if they could have succeeded in school just as well, they are discouraged from making that their priority because they feel they will never be as good as their older sibling. I still remember the tough fights about grades and music school that my brother and mom had, and I was mentioned way too many times.
Also if there is more distance in age, there is less pressure; their lower performance is more expected since they are so much younger and "eventually they'll catch up." This explains why there is a stronger effect for one-year gaps than five-year gaps. The gaps between my friends and their younger siblings are between 1 and 2. In our clique there are also younger siblings, but they are much further apart in age. These exceptions are the way it SHOULD work: younger siblings aren't constantly pressured into feeling naturally inferior and instead they can just learn from the successes and failures of the older sibling.
Finally, you mentioned that twins are underrepresented among your readers and also receive less attention from their parents. Well my mom gave both of us a LOT of attention as kids, so here I am.
What if the actual effect isn't intelligence, but being antisocial? Could it be that siblings with less time with another kid in the house had more introversion or more non-social pastimes, like reading or computers? I think this is a more direct match to the data. This also predicts that only children should be overrepresented; I imagine this is easy to check. I would also be surprised if there wasn't a question about introversion to compare to, though I don't know if a baseline is easy to find.
All speculation based on my own experience as an apparently exceedingly average ACX reader (late 20s, male, white, first born, programmer), but my guess would be that younger children consistently demanding more attention from parents socially conditions older children, especially first borns, to have a figure-it-out/do-it-yourself mentality (higher conscientiousness and industriousness?), which leads to a higher representation in your readership.
It tracks with my own experience that I was more independent and self reliant earlier due to the attention my parents needed to give to my younger siblings, and i think both a high delta in attention % between siblings after a younger sibling is born and the absolute difference in attention % may play a role, in addition to things that other commenters have mentioned like playing 3rd parent.
Interested in others opionions and experiences here, there should be a few other first borns in the comments, does this track for you too?
Every time this comes up I consider commenting, so I guess I'm commenting this time.
A few years ago, my mom (a PhD in developmental psychology) was observing my nephews and said offhand "it's so hard being an oldest child. You have to do everything first."
I asked her about that (being her oldest child) and she pointed out that younger siblings can watch their older siblings, and especially in early childhood, this gives them a lot of information on things like "if I throw a giant fit, what will happen to me?" And "how long can I get away with something before mom and dad notice?" And even "will I grow up? How long will that take? What will happen?"
Oldest siblings (and only children) are pushed to take on new ideas and experiences, that's just how the world works: you start with very limited data and figure it out yourself.
Younger siblings can, if they choose to, observe the results their older siblings got and coast, or at least use that data to limit their options.
So it makes sense for older siblings to be reading blogs about new ideas, technologies, and perspectives. The younger siblings out there will wait to see how it turned out for us before they get into it.
I think we were looking at it backwards. We were looking at this through the lens of, "why is the second born child less intelligent or why is the first born child more intelligent". I think it's worth checking statistically to see if a younger sibling makes the older sibling more intelligent. As in, having a younger sibling provides more learning opportunities from a fly on the wall perspective AT a level that is more easily comprehensible than the level that adults usually speak to their children, which is just outside of the child's current abilities. So, the hypotheses are, 1) having a younger sibling provides more easily understood learning opportunities without direct emotional cost of failure AND 2) a setting that perches the elder sibling in a relationship as an outlier with the potential to compound successes. So, we need to know what baseline IQ of only children are and see if the younger children are actually less intelligent than baseline or the older children are in fact made smarter by having a younger sibling.
I like the quote in the first paragraph, "correlate birth order with things." I use to characterize this kind of psycho research as correlating things with other things, happy to find it here. Folks, please remember, correlations are rarely zero in non randomized groups, so this stuff is much less interesting than you think. Moreover, I think I recognize a pattern, that the author of this blog tries to please us by basically telling us, once in a month, how smart we are. Nah, I'm not.
And, of course, the obligatory call for "we need more research" in the end, like a plumber who wants to solve the world's problems with more pipes.
Could it be reverse causation, that parents who have a especially smart first child are pleased and are more likely to have a second child whose ability reverts to the mean? Did someone do a comparison of all the first-born and second-born, whether they have siblings or not?
> it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one.
The developing brain is particularly sensitive to stress in the first two or three years. Stress exposure modifies the HPA axis to cause a permanent increase in the sensitivity of the stress response. You can see the effect in this graph from (Essex, 2002):
Transitioning from being an only child to being a sibling is an extremely stressful event, so you'd expect it to trigger that effect. Note that although we think of stress reactivity as 'bad', high stress reactivity is likely linked to later 'overachieving', as well as to a higher risk of mental health disorders in later life.
Another factor that may complicate things is childcare -- having a new baby probably affects whether the older one is placed in daycare. Center based daycare in particular is known to substantially raise cortisol levels. Cortisol rises are actually smaller for younger children (cortisol response hasn't settled down yet + lower bioavailability of cortisol) but the measured long-term effects on younger children are larger. So e.g. one causal study of universal childcare expansion of found
> this policy resulted in a rise of anxiety of children exposed to this new program of between 60 percent and 150 percent, and a decline in motor/social skills of between 8 percent and 20 percent.
First child is more likely to have "high functioning" autism than subsequent children (yes, I know the autistic community doesn't like that term, but unless they can come up with a better one, I'll use it in inverted commas). One theory is that this could be due to elevated testosterone levels in the womb (which then decline for later children due to the fact that the poor woman has other children to look after, which tends to reduce testosterone levels). I would be very surprised if this wasn't associated in some way with the higher readership of ACX. Full disclosure: I'm autistic.
Could it be that younger siblings are more likely to mention the blog to their older brother than the other way around. Because when you're the younger one, you're always looking for things that the older one hasn't done before you. The older one doesn't feel the push. This could be debunked if you know how people came to the blog.
Older siblings are by definition older than younger siblings. If older people are more likely to read ACX (which seems pretty plausible) then that's going to be a major confounder.
I wonder if it is more subtle than just quantity of attention - it's quite exciting doing things for the first time with your oldest, teaching them things etc. but when you get to younger siblings, you feel you have already done whatever it is, and it is slightly boring so you don't bother quite as much - the novelty value has gone.
Even assuming an implausibly hard selection effect where all ACX readers have IQs and openness of at least 3SD above the mean, I can't get such an extreme skew towards first-borns. 64%, not 72%.
But it can certainly explain part of it. The first-born effects of IQ and openness are known, and known to be small (roughly 1/10th of an SD) but they show up more in the tails. If 1/10th is an underestimate (plausible for a few reasons), maybe we can go to 72%, but it's still an implausibly hard selection effect.
But what's the mechanism behind the IQ and openness effects? They don't show up in every culture (Botzet et al. 2021). The study major effects (Barclay & Myrskylä 2016) show up in Sweden, or I would have considered that perhaps in the US with the high cost of tertiary education, first borns are more likely to have their parents be able to pay for it.
> n <- 1e8
> bo <- rep(0:1, each = n/2)
> ops <- rnorm(n, 99, 14.98) + bo * 1.5
> iq <- 99 + 0.3 * (ops-100) + 0.95 * rnorm(n, 0, 14.98) + bo * 1.5
> I additionally tried to compare two different types of social firstbornness - one where no older siblings lived in the house when you were growing up, and one where your parents had never parented another child. There weren’t many people discordant on these two measures (29 vs. 20 respectively), but for what it’s worth, the ratio was in favor of the first type.
I can't tell what this means. As far as I understand the terminology, the set of "people discordant on these two measures" unambiguously refers to every subject whose answers to question (1) and question (2) do not match. But that is a single set of people which cannot have population 29 and population 20. Who's in the group of 29? Who's in the group of 20?
> So for example, since the older sibling will always be smarter than the younger when they’re both young children
This claim can't pass a laugh test. How long did it take your little brother to be better than you at playing piano?
Great post, but I’ve got 3 kids and my immediate n=1 explanation didn’t really fit with your 2 suggestions. Seems to me it’s explained by the relationship dynamics of having a sibling but is NOT really to do with differentiation from each other. Young children who are 2nd siblings and relatively close in age to no. 1 seem to get a huge proportion of their social and intellectual development from the older sibling, regardless of gender and differentiation. I think that that close bond and dynamic reduces their drive to seek new sources of information (such as ACT) because the older sibling has such a strong influence in shaping their frameworks for viewing the world - even when they actively/ innately differentiate from the older sibling’s frameworks. In addition, the older sibling becomes accustomed to socializing the younger into their (older sibling’s) developing discourse. They are likely to feel rewarded/ fulfilled for this from the younger sibling’s receptiveness to taking in the info from them. This creates in aggregate a lasting disposition to seek new sources of info. Again, it’s easy to see that this may only play out within narrower samples, such as your readership, or with specific classes of info, but be lost at the general population/ broad context level.
My observation: The first child learns to be a boss by bossing around their parents first.
New parents want to be good parents and attend to their child, so they listen for what the child wants. They have time, attention and no experience at parenting at this point.
That first child can end up running the parents lives. And with that experience, any later children will be less experienced at being the boss and the parents will be more experiences at rearing children. But at the same time, the first child has already learned to dominate and doesn't like giving up that power. The second child might rebel and try to take a different path in opposition to the power of the older sibling, but a third or fourth child has to fit in some how. After all, the decision-makers, oldest child, parents and second sibling will make the rules.
Anyone care to comment on their observations of first child being the boss of the family?
As the technically ‘middle’ child of triplets (ten minute age gap solely due to birth weight) this birth order research always seemed a bit silly to me, but I suppose that’s mostly because of my personal unfamiliarity with the phenomenon of sibling age gaps.
From what I remember (being the 1st, and completing fitting the findings: I read ACT, I am in STEM while my brother choose a more artistic path), we should not look at parent investment or anything parent related (which fit well with parenting generally having little effect), but at direct relation between siblings. We formed a 2-member gang with my brother, with the eldest (me) the natural and not challengeable (at least until we were both past 17) leader. I think it fits my model of genetic>peer>parent in term of relative influence on every psychometric, when peers are siblings and later friends/schoolmates. Your siblings are part of your peers, the most important or even only one before 6yo...
The only thing I find quite strange in the data is that I expected a huge difference between same sex and opposite sex siblings: The brother sister dynamic is very different than between brothers (among sisters I do not know because I have no direct experience nor first hand observation among my friend's families)
It's often said that all of the original seven Mercury astronauts were first borns or only children and 14 of the next 16 American men into space were the same. But I don't see a link to a study.
As a Catholic Baby Boomer, my being a (rare) only child was a big deal when I was a kid in the 1960s. My friends assumed I got more presents on my birthday than they did (which I probably did). Adults were always telling me I was emotionally deprived by not having any siblings (which I probably was)
Now that only children are common, I never about them anymore.
Maybe for many younger siblings, if they do nerdy things at home, they get teased by their older sibling. And then "not being a nerd" might become part of their identity. But IQ other major life stats stay the same. This hypothesis would weakly predict that male dancers are much more likely to be older siblings.
It seems kind of strange that the focus is all on intelligence and academic achievement. The effect of birth order on readership of this blog (71/29) seems to be much stronger than for physics laureates (60/40) . While we might like to think that reading ACT is as good a proxy of intelligence as a physics Nobel, it suggests to me that it's a more specific personality trait that first-borns tend to have that correlates with attraction to a weird rationalist blog.
An interesting birth-order sports anecdote is Fernando Valenzuela, the Los Angeles Dodgers baseball pitcher who caused a sensation in the early 1980s. He was the youngest in a family of 12 in Mexico. He had one of the dumpier bodies you ever saw on a famous athlete, but was a baseball genius.
His older brothers were ardent baseball players too, but they had to go to work when still young. But Fernando was the adored baby of the family and was allowed to do nothing but play ball.
A possible overlooked confounder here is age. I'm 19 the oldest of 4. My younger siblings aren't at the age where they'd understand ACX.
As for your average 33 year old ACX reader you can suggest that many of your readers came on board in the Golden age of blogging ~10 years ago when their siblings were too young to come on board.
Is there some "recommended" way of sharing analyses? I'm curious about the the bio/social split, if I find something interesting I'd like to share.
I'm looking into it because I was a bit confused by Bucky's part about the biological vs social effects. If I get it right, the point of their selection (bio > 0, social = 0) is to filter people who had biological siblings at some point, but currently have none? I get that this would "isolate" the purely biological effects, but it also seems to introduce all kinds of other biases (it's not really representative of the general population) and additionally it doesn't even mean that there were no social siblings *at a previous time* in which it could have had an influence.
(btw the link to the CSV file in the old blog seems to be broken, excel file is fine)
Of my three kids, each 21 months apart, the younger two strongly tend to do what their older siblings are doing. They learned early on that to imitate is usually a good choice, so they do it a lot and it serves them well. The oldest imitates adults of course, but not nearly as automatically, because she knows many things we do she cannot or is not allowed to do. What she does do, however, is explain things to her younger siblings and give them instructions. That's what she got from us and it's harder than imitation but I think she has learned to think in that way.
None of them are in school yet, but I expect the oldest will find explanation-heavy subjects like math and physics slightly more intuitive than imitation-heavy subjects like music and physical education, and maybe her younger siblings will tend to go the other way.
Of course the ratsphere is super into explanation and I would argue it grossly neglects imitation. When we try to persuade, we try to craft excellent explanations, rather than build shiny role models to champion beliefs we want others to share. But much, arguably most, of human learning in the general population happens through imitation. Especially on ethical matters.
Could sleep disturbance in infancy be an explanation? When you are the firstborn, your parents try very hard to avoid waking you up, and you enjoy uninterrupted sleep. When you have a toddler sibling, you get waken up all the time. If uninterrupted sleep is important for infant brain development, it would explain why the effect disappear as age gap increase (a 5 year old can keep quiet, a 2 year old can't), and it would explain the twins (twins wake each other up all the time).
Could there be some selection effect (at least for ACX readers)? Readership is smart and in an age range such that a smart older bro also reads ACX but the smart younger bro does cooler other stuff(?) Accelerating change of internet, older generations more similar than newer, I dunno.
I guess I'm an aberration. I wasn't around for Slate Star Codex, but I read this blog. I am the third of three siblings in order of birth. I know for certain that one of the others doesn't read this blog because he's dead, and I doubt the other one does because he's not a big blog reader and mostly not interested in even the wide variety of subject matter covered here (if you start covering the NFL and military matters a lot, he might notice).
I think that Caplan and others tend to overstate the results of the research he presents. I don't remember the effect sizes of the top of my head, but I think his data indicated that something like 1 SD "better" parenting led to 2-3 point increases in IQ. This is a much more modest effect than most people's intuition, but still significant, especially for tail outcomes.
The social sibling effect could easily raise the IQ of first borns by a couple points, which is going to lead to noticeably skewed ratios for the tails. If, among well educated parents, the average 1st-born IQ is 114 and 2nd-born is 110, then among IQ 140+ individuals who are 1st or 2nd born, 65% will be 1st born.
At least for Nobels, etc., I'm going to blindly guess it's the differentiation thing.
I know both me and my (younger) brother were absolutely determined we weren't going to do STEM related stuff because our dad was an accomplished programmer and adopting his profession in a world of infinite choice felt somehow medieval.
But it turns out genetics is strong. We're both garbage in our chosen careers because young folks stink at choosing careers. But we've both managed to fall into that kind of work later in life.
In a family that was more traditional (as I gather traditionally successful folks' families tend to be), I would have been pressured into my dad's profession (and inherited his business contacts) while my brother would have had to work something else out.
Do I think that's a recipe for general success in a typical family? Force your kid to do what you do? Absolutely not.
But when talking about people who perform at the very top of their fields, probably genetics and nurture both have to be moving in the same direction. And really you can only do that kind of intensive training with one kid, and probably you pick the first one.
Also a new paper about IQ & birth order finds effect even controlling for family size (which is important because it was said family size-IQ relationship produces the IQ-BO statistical artefact):
It seems like there is an assumption being smuggled in here, namely that “reading SSC is correlated more with intelligence than some other trait.”
What if that other trait is, say, conscientiousness, or being thing-vs-people oriented?
Like, what if older siblings are less likely to be as people oriented because they didn’t have someone a few years older than them as one of the most interesting, salient features of their environment?
I’d love to see if the “first borns are overweighted” thing is true even if you filter out people who put themselves on the autism spectrum. That’s the approach I’d be taking - I’d try and find subsets of the data where the trend dissappears.
This is only slightly related, but... Do first-borns tend to partner with first-borns? This is a trend I've noticed in my family and wondered about before. If there is some set of characteristics associated with being the first-born, it could be that people with a lot of those might be attracted to other people with a lot of those as well. This could explain not only my observation but also why these people clustered together as this blog's community.
With infinite resources, we could also survey a whole university, say, and see if people's chosen major has predictive power over their birth order. I think someone already mentioned this, but I get the feeling first-borns are more likely to be pressured into studying something traditional and "safe" than their younger siblings.
What about the likelihood of finding only children in your sample? If hypothesis 1 is true, we should observe more only children when controlling for the relevant variables (that is, considering that only children are possibly more likely to come from unmarried couples, short marriages, etc).
Some people commented on the possibility of a "mentoring effect" for first-born children. If only children aren't more likely to appear in the sample, then that hypothesis could be more likely.
I also think about other variables that are not related to intelligence. Like some readers mentioned, the likelihood of the older sibling finding more introspective hobbies. I also consider the likelihood of the younger sibling learning how to be more "charming" and social in order to get more attention and differentiate himself from the always older and more intelligent sibling.
"One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower? If it’s about having quality time alone with Mom, someone with a sibling one year younger than themselves only got one year of quality time; someone with a sibling five years younger got five years. But it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one. Either the first year is very important, or I’m missing something."
Babies and toddlers are higher-maintenance. If the older sibling is already seven or eight when a new baby arrives, the baby obviously has more pressing needs, and the parents will in fact switch tracks to doting on the baby, possibly growing somewhat neglectful of the older sibling. Also, a much older sibling is old enough to, themself, help care for the baby, which will help smooth things over; a two-year-old is pretty useless (and sometimes actively harmful) around a newborn.
My explanation is that first children are required to take the lead on a whole host of situations where the siblings are involved. By taking the lead, out of necessity more often than not, the other children are relieved of that duty. That trains the younger children to be followers and the older children to be leaders. This explains why children a few years older create a stronger tendency, and also why after seven years it drops off - too little difference makes it less obvious who is in charge, while too much difference reduces interactions.
Why does this affect ACX readership? I think this blog interests people who are trying to figure out the world and make decisions about practical and moral effects. For someone who thinks that's important, there's a clear reason to follow the blog. For someone trained to let others do that work, then there's much less reason to follow a blog like this.
I’m an older sibling but I can’t imagine my younger brother, who has a higher IQ, earns more and is generally more successful, taking an interest in this blog. I tend to experiment a little more, have wider interests and deep dive into obscurity whereas he does the normal stuff very well
Wild. The one trait psychologists agree is known to be causally influenced by birth order (male homosexuality) is the one most accepted to be biologically and not socially caused?
" Firstborns get more quality time with their parents during the first few years of childhood."
I am puzzled. You seem to have an assumption that reading SSC makes firstborns better in some sense. But maybe it is something not-so-glorious that happens because the firstborns get more undivided attention of their parents: I can imagine the undivided attention makes them prone to navel-gazing and overestimating the extent their personal subjective experience and thoughts in general are super special and important and worth of loudly explaining to everyone around? Or, in other words, increased interest in philosophy (edit, and lets be realistic, strong political opinions)
The effect would be then naturally strongest in people who were the only child in the family. Eldest sibling has to learn to share when the siblings are born.
Does the data show there are more SSC readers who had no social siblings, compared to overall amount of them in the respective age cohorts?
I'm really surprised that this (IMO very weak) conjecture is getting a pass:
"Given that readers of this blog are highly-educated (about 37% have masters or PhDs) and mostly in STEM (41% programmers of some sort), plausibly birth order affects something about intelligence, education, or STEM orientation"
I didn't take the survey. Did you ask if the siblings have advanced degrees or work in stem? Have you directly addressed the possibility that older siblings might just enjoy reading blogs more? Or as another user points out, be inclined to take surveys more? Or spend time on using the internet more? Or any number if other factors?
I guess I am the only woman and mom here and oldest daughter of a line of oldest daughters, and I had to smile a little because I never bullied my younger siblings: in fact in many times I was their mother and nurturer when I had to babysit for them. Now my sons.. well I see what you are talking about: though i always encourage them to get along: it was the second son who was the bully if any of that went on.. well gotta go.. yes. that is just our little story: circumstances vary.. have doctor's appts. today.
Anecdotal, but this makes complete sense when it comes to my childhood. Younger of 2, both pretty intelligent.
When at a young age my brother discovered e.g. that you can use strategy in games, he found that it let him win every game against me, so he focused on that discovery, and soon even won some games against my parents.
When at a young age I discovered that I could use strategy at games I found out that it does not matter, I never won a game not entirely on chance no matter what I did (because my brother of course by then was way better at strategy). So I stopped playing Risk, or Chess, or any games like that after a while, because what fun is it if you never win?
Sports was similar.
So my brother learned young that if you dedicate yourself to something, you can excel. Tends to produce a strong work ethic.
I learned young that what I do doesn't really change how things turn out.
You may not be surprised that his academic achievements surpass mine...
From my experience as a South Asian/East Indian immigrant (not necessarily high-income) is that among my first cousins on both sides, the oldest of the family is always the most 'traditionally successful' in levels of education, type of field, and income. This is regardless of gender or varying family income or significant life events.
Culturally, there's an idea that the oldest needs to make it for the family and the pressure is intense to do really well in school and everything else. I am not American either, so I can't imagine how much more formalized that gauntlet is with US-style admissions, etc. Perhaps there's something similar for Western families but less explicit and less tear-inducing.
in the developmental psych literature, does parental pressure itself do better than parental investment in the form of Advanced Einstein baby toys or reading books? Its hard to disentangle the two, of course both nature and nurture-wise.
I think some consideration to the ideas outlined in "Deep Nutrition" a book by Dr. Cate Shanahan which talks a great deal about the findings made by Dr. Weston Price should be included. The idea is that nutrition plays an enormous role in physical health and intelligence. Their assertion is that inadequate birth spacing (less than the 4 years they consider ideal) means that the mother is nutritionally deficient which is then passed on to the child creating less than ideal conditions for proper growth and maturation. I am by no means an expert, but I think this merits discussion.
It's fascinating to see this effect in the data - it's *quite* clear in my own life. I'm the oldest, a lifelong nerd. One of my brothers is two years younger and always rejected academic stuff - not necessarily less smart, just much less interested in it. Then my other brother is several years younger than both of us, and pretty nerdy. Point for point reflective of what we see in this data.
A major difference that I don't see in the comments below is that first-borns with reasonably small age gaps are always a bit further along than their siblings. If you're a parent and you want to teach something, it is very likely the first-born who is most able to learn it. If an opportunity comes up and you're trying to figure out which of your children is best positioned to take it, that as well is most likely to be the first-born.
"Given that readers of this blog are highly-educated (about 37% have masters or PhDs) and mostly in STEM (41% programmers of some sort), plausibly birth order affects something about intelligence, education, or STEM orientation"
Well, if I didn't have Imposter Syndrome beforehand, I do now! Should I bask in the reflected radiance from the smart and successful, or ask 'what the hell am I doing here?' 😁
"This was surprising, because at the time lots of studies had shown there weren’t really birth order effects (that is, firstborn siblings had no major personality differences compared to laterborns)"
What were those studies? Do they seem to have been decent work?
The question that I'm really interested in: where are the younger siblings filling out surveys? Is there another blogger (or vlogger) that has that audience? I'd like to find them.
Another reason your "trollish" concern about twin studies doesn't get us out of the problem is that adoption studies tend to find the same results as twin studies re the low effect of shared environment.
> Followup research by Less Wrong user “Bucky” determined that the effect fell off with age gaps; the closer in age you are to your sibling, the stronger an effect birth order has.
Some supporting anecdata: I'm the firstborn in a family of six with three triplet younger brothers who are two years younger than myself. Interestingly, the differences between my three fraternal triplet younger brothers are stronger than those between the three of them and myself, and those differences really do line up with the observations made in this essay by multiple metrics.
If I were to identify a cause, it might stem from my parents consistently treating the elder among us as "more mature" and frequently giving us more responsibilities while doing the opposite with the younger, going as far as actively taking away responsibilities. (Yes, they did this even though my three brothers were pulled out of the C-section mere moments apart.) As we grew, we'd reinforce this dynamic among ourselves, often as justification for why the elder deserved certain privileges or why the younger could neglect certain duties. Without a doubt, this sort of treatment had significant effects on all facets of our psychological development, both cognitive and emotional.
I have noticed that the youngest sibling tends to be the "coolest" - i.e. more popular, social, etc. Possibly because they have an older sibling to teach them, hence the stereotype of the cool kid who knows about sex and alcohol because of his older brother. Others have already mentioned differences in parenting, which could contribute to this as well (parents are more lax with rules as # of kids increases -> younger kid spends more time partying and less time studying). Not sure if this is a real effect but perhaps the birth order effects noted here are not so much about older siblings being smarter or more STEM oriented but their younger siblings being less so.
I don't know if you account for half-siblings here and whether this is on the maternal or paternal side.
Maybe scenarios with a biological sibling but not a social sibling are disproportionately of type: dad has a child from a previous relationship but doesn't have custody, has second child in a subsequent relationship.
Dude, isn't the simple and obvious explanation that the older sibling develops a leadership role and therefore has to be more serious and intellectually-inclined? As opposed to comedy or sports?
I'm not sure what the biases in this kind of analysis are, but as a control group I'd be happy to see it done on other blog readerships or other self-selected groups.
Two of my children are quite close in age. They are close enough when they were small it was easy for them to forget that there was a significant age gap. So the older one was convinced for years that he was really smart; and the younger one was convinced for years that he was an idiot -- when actually they're about the same. Also yeah, they get the "oh, reading big science book's is something my older brother does" factor too.
One hypothesis I though of was that. In the ancestral environment, there was a need for different types of skills and personalities, but by the time someone was old enough to see for themselves which personality types the tribe is short of, it is too late for the brain to make the necessary adjustments. One way around this is for children, in early childhood development, to look around and see what personality types and skills surround them, and then pick complementary skills. Since most young children spend most of their time with siblings, this would create the effect. This would explain why sex doesn’t seem to matter, and why age gap does— children spend more time with siblings closer in age.
Source: oldest in a family of four, each of my siblings has a personality strong in the thing that the sibling one above them is weakest in.
Scott could see if this is true by, in the next survey, asking people how much time they spent with their family in early development, versus, say, a day care, and then seeing if more time = stronger effect.
The ideas I see are interesting in terms of why older siblings would seem smarter or more interested in STEM... but in general I think it would be useful to ground them back to how exactly they would increase their chance of reading this particular blog. This blog ends up having a STEM stereotype, but actually the content is pretty varied: the biographies of dictators, cost disease, drug discovery and pricing, "Untitled", "You are still crying Wolf", Unsong-adjacent and Fifty Swifties...
Another issue is that maybe older siblings are more interested in filling in surveys? There are older-sibling stereotypes that they have an inflated sense of self-importance; and stereotypes that they have an inflated sense of civic responsibility -- if either were true then that could change it?
I think probably the biggest selection factor on your blog is an attention span? The style of burying the lede deep into the twentieth sub-paragraph (which I'm not knocking -- I enjoy) is the opposite of what pretty much everyone else does -- it is the opposite of clickbait, and means that you normally have to read a few paragraphs in before the hook -- and I have always imagined this is one of the reasons the comment section here is so good. Again, it would make sense to me that older siblings have a longer attention span. If the first child has two parents to entertain them. The second child has two parents and an older sibling to entertain them.
I was wondering about networking effects. I know about this site from word-of-mouth. How do other people generally know about it? Do older siblings have larger networks? What I generally observe in families I know is that older siblings are often closer to the parents' generation than younger siblings, who seem more distant socially somehow -- so in this sense, I guess they have a network boost. I probably get send more links by my parents, aunts and uncles, than a younger sibling of mine would -- maybe I should ask. Again anecdotally, but it seems to me that connections travel up through older siblings more often than down through younger siblings. Maybe it's a seniority thing: it seems cool and interesting to get to know your friends' older siblings -- they're always at the next stage of life; but maybe not so much their younger siblings?
My immediate thought is that second borns grow up in a complex social situation with peers. That may require them to develop more complex social skills/pay more attention to interpersonal situations. That may skew later career choice away from STEM fields. (More specifically some non stem fields gain attraction while stem stays the same, losing relative attraction)
Even Bryan Caplan concedes that the signal that this paper picks up is sound, and weakens Caplan's hypothesis somewhat.
It says that although parental income, environment at home, etc does not affect future earnings as much, one thing that invariably does affect future earnings and achievement is the quality of kindergarten training. I suspect that it is this effect that is even stronger at younger ages (say the first year of the child's life), which is what Scott is picking up in this survey.
First-born children face more pressure from their parents to do something practical and conventional with their lives.
Meanwhile, the key demographic of readers of this blog is "Frustrated philosophers" -- people who wanted to study philosophy at university but wound up doing computers instead.
It seems to me that ACX doesn't select for intelligence, it selects for a certain kind of intelligence and temperament. Wide interests (I think of that as fannish), a tendency to want to look at things from the outside, and at least some tolerance for liberal/anti-progressive politics.
Do venues which have smart people but differ on the other factors still tend to have a lot of first-borns?
Unless you randomly selected people to answer the survey, could there be a confounding factor that first borns tend to answer surveys and such?
Being the 3d of 3, my opinion wasn't worth much at the dinner table. And I don't rate Amazon products or give Yelp reviews. Could being higher up in birth order make a person more likely to answer ? That would tip the balance in their favor if they tend to self select
i'm the youngest with a 9 year gap to the closest sibling, my siblings were basically like extra parents/ guardians.
I think a good comparison for more research would be to compare with only children. To disentangle if it's to do with 'lots of attention when young' vs 'responsible for someone younger than you' vs 'most competent person around your age in your house' among other things.
Having an older sibling close enough in age helps you develop better theory of mind earlier, which makes you grow up less nerdy, and you are less likely to end up becoming a programmer who reads acx
I didn't read all the comments so this was probably raised before but since you are looking for differences in whether someone reads your blog or not one obvious question to ask is how someone came to read the blog. Specifically I read this blog because it was recommended by my older brother. Perhaps there is some asymmetry in recommendations from older to younger siblings and vice versa. (Although that would mean my case goes against the trend.)
(P.S. I did not answer the survey and I am guessing my older brother didn't either.)
Maybe the first borns are just higher variance so they show up more in more selective extreme groups? And maybe that's because the parents pay consistently more attention to the younger one when both have already been born? Or because of something related to the dynamics of having and older / younger brother, like bullying, competition.. or the younger one having to follow the steps of the older one, inheriting the toys that the older one chose and liked, etc.
I don't think it's regression to the mean where people have a second child only when the first one turned out a decent experience, because I think most people that have a child have more than one, right?
It's not IQ or general smartness that is being selected for. What sets this group (and the Nobel-physicist group, and the great-mathematician group, and maybe the Harvard-philosopher group) apart, as I mention in my reply to Nancy Lebovitz, is that we are that ultra-nerdy rationalists, very often STEM nerds in particular, and we like to Think about Things. Which, really, is kind of weird.
A firstborn child, or a social-firstborn or a younger child with a large age gap, spends the first years of its life trying to comprehend a world full of Weird Interesting Things. Some of those things are called "grown-ups", which are technically "people" but from a toddler's POV they're a completely different order of being. They're weird interesting things.
A (not too much) younger child, spends the first years of its life in close company with at least one other *person*, a person not too different from themselves. And if there's a Weird Interesting Thing that they need to understand, maybe the best way to do that is to learn from that other person.
So maybe the firstborn child is more likely to adopt a Thinking About Things outlook on life, rather than the much more common Understanding People outlook. They're not *smarter*, they just use it differently. And really, even most of the firstborns will wind up in the Understanding People group; that's just how people are wired. But if you're selecting three-sigma outliers in Thinking about Things, you're selecting for firstborns.
This seems to me at least as good a fit to the observed data as any other hypothesis, and better than most.
Well, the obvious hypothesis that comes to my mind is parental expectations. One thing that is very obvious about parents is how much they chill out between Child #1 and Child #N, for N > 2. For the first (or, worse, only) child, parents' expectations are sky-high.
My kid is going to be some combination of Einstein, Mother Theresa, and Winston Churchill. Since he needs to get a PhD from Stanford by age 25, he needs to graduate from Harvard at 20, which means he needs to go some super-competitive magnet high-school after skipping a grade or two in a superb private elementary school....so damn it we better get cracking at getting him into that enrichment pre-school that has only people with PhDs changing diapers -- he's already 3 years old for god's sake! And stop giving him the regular mashed peas, he needs the choline-vitamin E-probiotic fortified 100% organic mashed peas harvested from the slopes of Vesuvius by the lineal descendants of Aristotle. You want him to turn out ordinary??
Comes child #2 or #3 and it's like hey honey little Billy was eating laundry soap again and he looks unhappy, could you maybe get him some water to wash the taste out?
I remember Gilovich talking about birth order effects in his Behavioral psychology class. He seemed pretty convinced. He liked the explanation that birth order effects stem from having to teach the younger sibling things and that you can see the same effect with only children in the US whose parent's first language is not English. They had to teach their parents.
Could the answer be hiding in plain sight? If you were to start club called the "Older Than 10 Club", wouldn't you expect the membership to be skewed towards older siblings? Either:
a) if both siblings belong to the club, they don't bias the sample
b) if neither sibling belongs to the club, then they don't appear in the data
c) if only one sibling belongs to the club, the older one is more likely to be a member, on account of the fact that there are more people older than 10 than there are people younger than 10.
Maybe this blog is most attractive to people who are older than a certain age, on average, and that accounts for the bias?
"The current scientific consensus is that parental investment in the early years of life doesn’t really increase IQ or educational attainment .. This research challenges those assumptions. If it’s right, the difference in parental attention between an only child and a child with siblings seems to have noticeable effects later in life."
The implication here is that birth order -> IQ -> SSC reading. As a first-born SSC reader I like that theory, but I can think of some more plausible relationships.
Maybe first born have had less socialization and are more likely to enjoy solitary interests?
I can propose one more hypothesis. Firstborn are not more intelligent, they try harder. They grown up being more intelligent than their siblings, their "intelligence" is a part of their self-image. Yeah, now I'm talking about myself. And I'm a pretty severe case of it, up to panic attacks when I didn't manage to hold an image of a very smart person. People really asked me "what happened? why you gone all white?". Yeah, I'm talking now about me, not about all firstborns, but I'm pretty sure that one of two big reasons of my condition is me being firstborn. I was responsible for me and my brother all the time. If my brother fall into a river, than I was asked "how it happened, and why I didn't prevented it". It was like my brother fall victim to my stupidity. It was not literally said, but "you need to be smarter" was one of phrases I heard a lot of time being a kid and in my teens. I rebelled at 14-15 against this responsibility. It is a different story, but note that I rebelled against responsibility, not against me being smarter. It took me 20 more years to start fighting my self-image of an intelligent person.
So, my hypothesis is: firstborns try harder to seem intelligent, they develop the whole strategies how to be (or to seem) more intelligent than others. These strategies include "tactic" reactions to stimuli, allowing to hide their "stupidity" (like if I did not understand what happens, I give others a possibility to ask "what happens" or to say/do something that might help me to understand what happens, and I would try hard to be unnoticed). But it doesn't stop here, firstborns learn to be curious. In an academic sense of the world. To learn what other think about some problem is nice, when you forced to talk about this problem, you could make a reference to a few sources, lay out a few different opinions and then maybe even to verbalize your own thoughts on the topic. Or in other company it is better to "plagiarize": to express some opinions without references.
I told, that I'm a severe case, and I really do not know how bad it goes in minds of other firstborns. But what I'm trying to say, that it is not just "I try harder", it is how I live, it is who am I. I read ACE not because I need more smart thoughts cached, I read because it is fun. But it is fun, because I learned as a kid, that intelligence is my inherent psychological trait, and as a teenager I found ways to match to this trait. It is just conditioning.
I cannot say, I know, how to prove it. I'd try to get an operational definition for my condition, to get a way to measure it by looking at behavior. Then to use it on many people, and to study those who hit high scores on the condition -- let them fill a lot of questionnaires, find all the correlations. Then probably we could find an easy to measure trait which is highly correlated with the condition. And then we might find it in the data gathered here.
Though, there was mentioned psychological research of siblings? Did they tried to give some unsolvable task to siblings, while measuring time they spent on it before giving up? Or to place them in unexpected difficult situations, while measuring "smartness" of their way to deal with it. (I called it "smartness", but really it is not about smartness per se, it is about how they manage to look intelligent people.) It may be tricky to operationalize, but I believe it is possible.
1) if I understand Becky's comment correctly, the dataset contains more people with zero biological and some social siblings than the other way around, which is surprising to me and may indicate an important selection effect.
2) the whole essay seems to use "being a reader of ACX" as equivalent to "being more intelligent than the average in general", which doesn't sound justified by mere correlation. The fact that ACX readers are more likely to be highly-educated and also firstborns doesn't automatically mean that firstborns are smarter in general.
Most obvious answer I can think of is seniority dynamics. Confidence and success breeds further confidence and success, and the oldest sibling is always at the top of the hierarchy. This fits with the huge drop off we see between Sibling 1 and Sibling 2, and the much smaller effect when going from Sibling 2 onward.
I don't think parents have much to do with it. Kids get most of their social input from peers, not adults, and siblings - especially those close in age - are the most important peers of all.
"One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower?"
Yes, the first year is important, but also consider school/preschool: Age gaps over a certain number of years basically give the second child an experience more like that of a first child, since the first child is out of the house or at least more independent.
I thought it was interesting that the decline of the ottoman empire began within a generation after they switched from primogeniture to agnatic seniority.
As a first born with good general success compared to my siblings, the largest difference today is our openness to experience, and willingness to try to fix a problem. They are just as smart as me usually.
I suspect the openness part could be partially due to me not having much help solving problems when I was little, I had to do it myself, or it wouldn't happen (my parents weren't great at helping) whereas my siblings could always get assistance from an older person rather than do it themselves. Having good initiative on learning and doing pays compounding returns.
I'm doubtful parenting has anything to do with this, likewise infancy, as the effect gradually reduces over 10 years. To me the most plausible explanation is firstborns' requirement to figure out a lot of things on their own. This would inculcate increased amounts of "seeking for the truth"; trying to figure out how the world works. The closer in age a sibling is the easier it is for them to learn by example of the older sibling or to just be directly taught by the elder. A 15 year old would struggle to teach a 9 year old relevant things that the parents couldn't teach just as well.
Supports: This is a social explanation, not biologically dependent. It explains the smooth reversion to the mean rather than dropping off suddenly at some point (as an infancy based explanation might suppose).
Problems: I would expect a small amount of gender disjunction but that seems not to appear in the analysis.
Tests: The effect should decline in more communally raised children, where they have very close relationships with children their age (or one year older).
Disclaimer: I am an eldest with 3 younger siblings (none of who read SSC/ACX).
Here's what I think of the first born. Enneagram 8.
Challenger
Basic Fear: Being controlled or violated by others.
Basic Desire: To determine their own course in life. To protect themselves.
Eights want to stand alone, to have power over their lives, and to achieve their goals. They are extremely driven, resourceful, and propelled towards their vision and purpose. They don’t want to feel indebted to anyone, emotionally vulnerable, or in any way dependent. Autonomy and freedom are vital to their happiness; the only problem is that they may defy being vulnerable so much that they miss out on fulfilling relationships in the process. These types crave a sense of intensity in their lives. Whether they’re race-car driving or starting their own business, they enjoy proving naysayers wrong and testing their abilities and strengths.
In childhood, Eights felt that they had to grow up quickly. Early on they felt that they were in some way responsible for the welfare of their family. There was no time or safe space for vulnerability – they had to be strong. Survival issues were at the forefront of their mind. Being gentle, giving, emotionally open – these typical INFJ characteristics were probably repressed because it didn’t feel safe. In some way they felt there was a risk of rejection, betrayal, or pain if they let their guard down. They developed a tough, independent, hardened demeanor as a way of dealing with their pain.
Eights are in the Gut/Instinct triad of the Enneagram. This means that they have underlying issues with anger. While Nines avoid their anger and Ones repress it, Eights express their anger. They like straight-talk and directness and tend to be assertive themselves. When threatened or controlled they can become explosive and intimidating. They feel very defiant of any institution that tries to control them – and they may make life choices simply to rebel against that institution. Whether it’s dropping out of school because the teachers were too controlling, marrying someone a parent doesn’t like, or driving faster than the speed limit on a bad day.
Sincerely believe that its the forced leadership. In group play, (and many other situations) the older sibling has to take to the lead. This means generating play ideas, structuring play, and reinforcing play rules. This would explain why the effect is stronger when the gap is closer, and how it could be social without necessarily being based on parental involvement. I think that this could bias some personalities towards valuing things like intelligence and independent thought without actually being smarter (valuing intelligence might make you more likely to invest in your own, but wouldn't necessarily bump you out of your bracket). You might see some boosts in creativity from early practice - but the overall thing that gets affected is not the underlying skill but the perception of which skills are desirable. That would mean that your strongest sibling-order-effects would be in preferences - characters you relate too, ideas that draw you in, or blogs you read.
Father of two kids here, so my sample size is 1. However, I suspect that the cause is "bossiness". In my family, the younger sibling is the bookworm; she loves to read, and is by far the more STEM inclined. But the elder sibling absolutely loves to "mother" her, and always wants to be in charge of whatever games they play, even though the age difference is only 1.5 years. As parents, we have to constantly work to make sure that the younger sibling has a say in things. I would hypothesize that 10+ years of unintentional "leadership training", or conversely, "follower training", might make a significant difference.
Maybe older siblings are poorly socialized due to having no older siblings, thus more likely to be "on the autistic spectrum", thus more likely to subscribe to AC10.
If my first kid is smart I am more likely to have another one. Add some random distribution of intelligence between kids and regression to the mean and we have an explanation.
Another possible mechanism, which is biological, but not genetic, is the potential effect of early illness. Just anecdotally, my first child wasn't sick for the first year of their life due to lack of exposure to other kids, but I fully expect my second to be sick much earlier due to picking up things from the older one. I'd expect this to attenuate over time as the first is more able fight off infections before they spread to others.
If this is true, I'd expect this effect to vary based on when/whether childcare like daycare is used (and what type). Also does this vary over time? Were there birth order effects in the early 1900s, for example? How do they vary across countries?
One (anecdotal, unscientific) observation I have made is that boys with older brothers (this one is sex specific) tend to have more tenacity than those without. I attibute this to the type of rough play the boys tend to get into (much to their mothers' chargrim) wrestling, stick fighting, etc. The younger brother will almost always lose such games and yet is expected to play on anyway to grow stronger and hope for the sweet moments when he can catch the older brother off guard.
I would love it if someone could suggest a way to test this theory or even better actually test it.(The hard part I believe it's coming up with a suitable metric for "tenacity", I am highly skeptical of anything involving self reports)
"You may be able to think of others besides these."
Maybe older siblings compete with younger siblings in various ways, and, *being older*, naturally win. e.g. maybe older siblings are much more successful at bullying younger siblings than vice-versa.
Social first-borns are a third parent to their younger siblings. First-borns are replaced as the cutest thing in the household. This is the effect; not more parental attention. They become parent-like and get attention for being helpful instead of cute.
It's cool to see that the effect persists in the new data. It seems that we older siblings need to convince our younger siblings to read this blog!
I'm wondering, does the effect remain when you control for age? First siblings will be older on average.
Makes one wonder if primogeniture wasn’t arbitrary.
Some other nurture explanations I’ve heard:
- Firstborn siblings spend more of their early years exposed to and learning language from adults versus other children who are only slightly older.
- Similarly, firstborn siblings are more directly exposed to praise and expectations from their parents and other adults, vs the praise and social validation of another slightly older child. Thus they become more oriented to achievements that will impress adults, such as performance in school.
Are you sure that older siblings aren’t just more likely to try and please authority figures by performing thankless tasks like filling out user surveys ?
Maybe being older you get lots of opportunities to explain/teach things to a younger sibling, this makes you more reflective and self aware hence more likely to go into higher education get a PhD etc. The decline starting at 8 years might be because at 18 you move out and stop teaching your younger sibling things while they are still quite young and can be taught a lot of things, i.e, less than 13.
My personal hypothesis is that the greater uncertainty involved in raising a child for the first time leads to higher openness to new experiences. I'd guess this can go down a number of different paths in practice, but that cultures situated outside of the mainstream will be disproportionately firstborn as a result.
How do you know that "birth order" is not just a proxy for "age"? Maybe people who spent more formative years prior to smart phones are more receptive to long essays of the sort that you write.
Some thoughts:
- Nice work.
- First borns are part of the "parental teaching structure" of subsequent kids.
- and also competitors, cooperators and imitators. I have a 9 yo and 6 yo and I can tell you they are both forever different, on questions of basic personality/desires because they have a sibling. There are things they do/love/hate because of how their sibling feels about them.
- is there any value to looking at school situations (such as Montessori) that often mix age groups? A class room of all 2nd graders is going to have different "social sibling" effects than one that's 1st, 2nd, 3rd all together.
- and what about the past, when almost all kids were raised more or less in a group - a swarm of cousins of varying ages? Being the first born in a house that only ever has 2 kids is one thing. Being the first born in a generation of cousins probably has different implications.
- did you ask any questions about pets (insert snark about "substitute kids") in the household?
I wonder if Kevin Leman reads this blog.
You're only looking at 1/3 to 1/2 the picture. The interaction between the siblings, especially the role assumptions that go on.
Our children are 18 months apart. Just before our second was born, my wife took our daughter to the toy store so she could have a baby doll of her own, something that looked a lot like a real baby. Mom had the daughter give her baby doll a name (Baby Mike) ... OK ... with the thinking mom would have here baby, and our 18 month old daughter would have her own baby to mimic mom, instead of wanting to hold her baby sister.
Great idea, but wrong. Baby Mike went into the toy box to almost never return. Yes, she wanted to hold her baby sister, and we allowed this with close supervision, the older daughter was only 18 months after all.
But what happened was a total bonding, the younger grew up faster, as the protégé of the older, and the older did revert some especially when it came to diaper training. We had read about, and expected this.
I think there was growth and leadership developed in the older child, far vision thinking if you will ... which is pretty much what this forum is about.
The younger child didn't/ doesn't look to the horizon as much as she follows her older sister still in a lot of ways, they're 29 & 31 now.
And yes, I'm the elder of two, my sister is 16 months younger than I.
Whenever this topic comes up, I wonder how only children (no siblings) stack up against firstborns. What percentage of this blog’s readers are only children?
I’m also curious about how many female readers of this blog are only children vs male readers.
I saw those graphs and immediately thought of Benford’s Law.
In my experience youngest siblings can instantly identify each other. They have been strongly socially conditioned; they were always the cutest, they were always smaller than their siblings, and parents had relaxed relative to the first kid. They're used to losing arguments and having things not go their way (being younger and smaller, not necessarily more or less on track), unless they work disproportionately hard for it.
Some anecdotes:
1. My parents *returned* the gameboy I was given as a birthday present, but my youngest sibling was allowed to have multiple consoles.
2. Although I'm three years older than my sister and she's three years older than our youngest sibling, we all learned to read within two years; I was late, she was on time, and the youngest felt left out and taught themself to read at the age of two. (Those early digital books that highlighted and spoke the word at the same work wonders!) Now, of the three of us, 1 and 3 are the most avid readers. (But 2 got a neuroscience degree, she didn't get off easy!)
3. My dad taught us all to program at the same time; we all started with the same level of competence and quickly developed our own styles. Of us, 1 and 3 are employed as software engineers now; 2 lost interest. (This was also part of a larger experiment on us; in the early 2000s there was a theory that girls didn't enter programming because they didn't have a cohort, which my dad found to be a testable hypothesis, so he not only taught us but also most of my sister's school class. It did briefly keep their interest as a communal activity, but it's not clear it had any long term effect.)
I (a first-born) have also surrounded myself with disproportionately first-born friends, I find we're on the same wavelength. But I know I'm pretty unusual, both in general and among first-borns, so I'm cautious about extrapolating my own experience in that regard.
An explanation of the birth-order effect diminishing with age gaps, which still makes the primary driver of the effect parental attention, could be that the first couple of years of a child's life are the ones that require the most parental attention. A second child who is two years younger than their older sibling will get less parental attention than a second child who is six years younger, because in the first situations, the parents are having to deal with a toddler.
I think I was in your "several biological siblings, no social siblings" group, because of the large gap between my older sisters and me (fourteen years). I've often thought I got the best of both worlds growing up. In terms of parental attention, it was like being an only child, but my parents were still experienced parents, and knew what they were doing because of my older sisters.
> One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower? If it’s about having quality time alone with Mom, someone with a sibling one year younger than themselves only got one year of quality time; someone with a sibling five years younger got five years. But it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one. Either the first year is very important, or I’m missing something.
The lived experience of parenthood makes it pretty obvious why small age gaps have larger effects. The mother of a newborn and a 1 year-old has less attention to devote to the newborn, because the 1 year-old is extremely needy. A mom who read dozens of books aloud daily to the firstborn 6 month-old probably reads zero to the second born at 6 months if there is also a toddler in the house. The newborn gets a lot more of Mom’s attention if the sibling is a 5 year-old able to feed herself, use the toilet herself, play without needing Mom for more than ten minutes at a time, etc.
My theory is that the average intelligence of the other family decreases for subsequent children. The first born interacts with two adults; the second born interacts with two adults and a child.
I have one immediate reaction to these questions.
Hypothesis: "Firstborn" children are recuited as deputy parents when younger siblings come into the family.
I speculate: Consciously, or unconsciously, the oldest feels more like an adult from that point on, and may feel and behave more responsibly, and also may enjoy feeling more "accepted" by their parents into the world of adult society. Maybe younger children never feel this (although families where i.e. the oldest girl ends up with lots of maternal responsibilities are anecdotally common.) Maybe younger childen have a kind of extended childhood vs an "accellerated" childhood for first-borns.
On the same topic, research published ~5 years ago looked at athletic achievment by siblings in US professional sports. (link below...I think, it seems not to be showing up...) They found a HUGE positive effect for YOUNGER siblings, especially the second child in a family. (Note: this study had vastly more male children and brother-brother pairs, for obvious reasnos, but IIRC the effects were just as strong for the few female athletes in their study.)
Several reasons were posited, the two salient ones were:
-- Practice effects: The younger child is often playing with the older, and with other kids several years ahead, this is very tough competition and an intense learning environment.
-- Parental / Family experience: Parents learn how to navigate schools, leagues, coaching, sports-bureaucracies in general, and the younger kids get fast-tracked into the best opportunities.
For me, the absurd number that stood out was this: In US Baseball, 700 (!) pairs of brothers have played in MLB. The younger brothers, collectively, attempted 10x more stolen bases than the older.
https://fivethirtyeight.com/features/why-are-great-athletes-more-likely-to-be-the-younger-siblings/
Thomas Sowell talks about this in "Discrimination and Disparities". Here's what I highlighted in that chapter:
'A study of national merit scholarships, for example, found that, among finalists from five-child families, the first-born was the finalist more often than the other four siblings combined. First-borns were also a majority of the finalists in two-child, three-child, and four-child families. If there is not equality of outcomes among people born to the same parents and raised under the same roof, why should equality of outcomes be expected - or assumed - when conditions are not nearly so comparable?
Such results are a challenge to believers in either heredity or environment, as those terms are conventionally used.
IQ data from Britain, Germany and the United States showed that the average IQ of first-born children was higher than the average IQ of their later-born siblings. Moreover, the average IQ of second-born children as a group was higher than the average IQ of third-born children.
A similar pattern was found among young men given mental tests for military service in the Netherlands. The first-born averaged higher mental test scores than their siblings, and the other siblings likewise averaged higher scores than those born after them. Similar results were found in mental test results for Norwegians. The sample sizes in these studies ranged into the hundreds of thousands."
(...)
"Consider how many things are the same for children born to the same parents and raised under the same roof - race, the family gene pool, economic level, cultural values, educational opportunities, parents' educational and intellectual levels, as well as the family's relatives, neighbors and friends - and yet the difference in birth order along has made a demonstrable difference in outcomes.
Whatever the general advantages or disadvantages the children in a particular family may have, the only obvious advantage that applies only to the first-born, or to an only child, is the undivided attention of the parents during early childhood development. "
Dr. Sapolsky mentions this exact phenomenon in a lecture series on human behavioral biology. The data discounts fetal resource depletion and parental attention. He indicates that the current working hypothesis is that the firstborn is forced into a tutoring or mentorship role.
Here's the relevant clip (can't remember which lecture it's from): https://www.youtube.com/watch?v=lj4D5haCkkQ
Here's the full series: https://www.youtube.com/playlist?list=PL848F2368C90DDC3D
Edit: double posted the series link, fixed.
Second edit: The full lecture link is included in the clip, 8. Recognizing Relatives.
Hey, I'm one of those edge cases. I'm the oldest of two siblings, but my mother gave a child up for adoption 8 years before I was born. And I'm a classic older child, so one point for some sort of social vs. biological effect.
My guess would be that the difference is variance. Two populations with the same mean will be measured to have the same mean. This is often interpreted as no difference. However, if the standard deviations are different, the tails will look very different. In this situation, that would mean that first born have higher variance. Has anyone looked at the negative end of the spectrum? (As a reader, I’m obviously designating my end of the spectrum as the good side.) what’s the birth order like in prison populations?
Total non-sequitur but I've noticed the more elevated the habitat of a species is- the more likely they are to be polygynous
sample size himalayan marmots, Tibetans, and some birds?
this is mostly joking but also not
>One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower? If it’s about having quality time alone with Mom, someone with a sibling one year younger than themselves only got one year of quality time; someone with a sibling five years younger got five years. But it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one. Either the first year is very important, or I’m missing something.
An older sibling one year older is always doing fresh things, and their one year younger sibling is always just redoing the thing that just happened- there is no novelty, less enthusiasm etc. With a greater age gap, the older sibling naturally ages out of intensive parenting at some point during the younger sibling's development and the younger sibling gets more attention, i.e. older sibling goes off to college when younger sibling is in 7th grade, younger sibling is now effectively an only sibling.
Making my first comment because I have actually thought a lot about this lately. Some anecdotal data to introduce my own theory.
My buddies from school are all very analytical, competent, and successful. Three stand out and they are all firstborn. They also stand out because their younger siblings struggled more and were more rebellious. Add to this general trend a half-exception: my brother and I.
I am a twin. Technically, I'm younger, but I have always been more academic and I was the first one to read, so I was the one who started with a natural advantage. My brother has indeed been "more interested in excelling in areas other than school, like trying to cultivate a special talent that the firstborn [or in this case younger twin] doesn't have." I still remember crying when I realized I wasn't as musical as him and he is now a composer, yet alas, not a frequent reader of ACX.
So here's my theory: older siblings start off with a natural advantage in intelligence. So similar to your second theory (in twins that advantage is decided more randomly because they are otherwise so "identical"). However, younger siblings don't immediately start to differentiate themselves. Instead they are PRESSURED to match the performance of their older siblings. Some of them just can't compete and rebel. They are then led away from traditional marks of success. So even if they could have succeeded in school just as well, they are discouraged from making that their priority because they feel they will never be as good as their older sibling. I still remember the tough fights about grades and music school that my brother and mom had, and I was mentioned way too many times.
Also if there is more distance in age, there is less pressure; their lower performance is more expected since they are so much younger and "eventually they'll catch up." This explains why there is a stronger effect for one-year gaps than five-year gaps. The gaps between my friends and their younger siblings are between 1 and 2. In our clique there are also younger siblings, but they are much further apart in age. These exceptions are the way it SHOULD work: younger siblings aren't constantly pressured into feeling naturally inferior and instead they can just learn from the successes and failures of the older sibling.
Finally, you mentioned that twins are underrepresented among your readers and also receive less attention from their parents. Well my mom gave both of us a LOT of attention as kids, so here I am.
All I can say is the middle child is best.
What if the actual effect isn't intelligence, but being antisocial? Could it be that siblings with less time with another kid in the house had more introversion or more non-social pastimes, like reading or computers? I think this is a more direct match to the data. This also predicts that only children should be overrepresented; I imagine this is easy to check. I would also be surprised if there wasn't a question about introversion to compare to, though I don't know if a baseline is easy to find.
All speculation based on my own experience as an apparently exceedingly average ACX reader (late 20s, male, white, first born, programmer), but my guess would be that younger children consistently demanding more attention from parents socially conditions older children, especially first borns, to have a figure-it-out/do-it-yourself mentality (higher conscientiousness and industriousness?), which leads to a higher representation in your readership.
It tracks with my own experience that I was more independent and self reliant earlier due to the attention my parents needed to give to my younger siblings, and i think both a high delta in attention % between siblings after a younger sibling is born and the absolute difference in attention % may play a role, in addition to things that other commenters have mentioned like playing 3rd parent.
Interested in others opionions and experiences here, there should be a few other first borns in the comments, does this track for you too?
Every time this comes up I consider commenting, so I guess I'm commenting this time.
A few years ago, my mom (a PhD in developmental psychology) was observing my nephews and said offhand "it's so hard being an oldest child. You have to do everything first."
I asked her about that (being her oldest child) and she pointed out that younger siblings can watch their older siblings, and especially in early childhood, this gives them a lot of information on things like "if I throw a giant fit, what will happen to me?" And "how long can I get away with something before mom and dad notice?" And even "will I grow up? How long will that take? What will happen?"
Oldest siblings (and only children) are pushed to take on new ideas and experiences, that's just how the world works: you start with very limited data and figure it out yourself.
Younger siblings can, if they choose to, observe the results their older siblings got and coast, or at least use that data to limit their options.
So it makes sense for older siblings to be reading blogs about new ideas, technologies, and perspectives. The younger siblings out there will wait to see how it turned out for us before they get into it.
I think we were looking at it backwards. We were looking at this through the lens of, "why is the second born child less intelligent or why is the first born child more intelligent". I think it's worth checking statistically to see if a younger sibling makes the older sibling more intelligent. As in, having a younger sibling provides more learning opportunities from a fly on the wall perspective AT a level that is more easily comprehensible than the level that adults usually speak to their children, which is just outside of the child's current abilities. So, the hypotheses are, 1) having a younger sibling provides more easily understood learning opportunities without direct emotional cost of failure AND 2) a setting that perches the elder sibling in a relationship as an outlier with the potential to compound successes. So, we need to know what baseline IQ of only children are and see if the younger children are actually less intelligent than baseline or the older children are in fact made smarter by having a younger sibling.
I like the quote in the first paragraph, "correlate birth order with things." I use to characterize this kind of psycho research as correlating things with other things, happy to find it here. Folks, please remember, correlations are rarely zero in non randomized groups, so this stuff is much less interesting than you think. Moreover, I think I recognize a pattern, that the author of this blog tries to please us by basically telling us, once in a month, how smart we are. Nah, I'm not.
And, of course, the obligatory call for "we need more research" in the end, like a plumber who wants to solve the world's problems with more pipes.
Could it be reverse causation, that parents who have a especially smart first child are pleased and are more likely to have a second child whose ability reverts to the mean? Did someone do a comparison of all the first-born and second-born, whether they have siblings or not?
1. Is there any difference between a two-brother pair and a two-sister pair?
Some older brothers really haze the younger one. Surviving that changes people. I’m not sure it’s entirely gender-based but I think that’s a factor.
> it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one.
The developing brain is particularly sensitive to stress in the first two or three years. Stress exposure modifies the HPA axis to cause a permanent increase in the sensitivity of the stress response. You can see the effect in this graph from (Essex, 2002):
https://ars.els-cdn.com/content/image/1-s2.0-S0006322302015536-gr4.gif
Transitioning from being an only child to being a sibling is an extremely stressful event, so you'd expect it to trigger that effect. Note that although we think of stress reactivity as 'bad', high stress reactivity is likely linked to later 'overachieving', as well as to a higher risk of mental health disorders in later life.
Another factor that may complicate things is childcare -- having a new baby probably affects whether the older one is placed in daycare. Center based daycare in particular is known to substantially raise cortisol levels. Cortisol rises are actually smaller for younger children (cortisol response hasn't settled down yet + lower bioavailability of cortisol) but the measured long-term effects on younger children are larger. So e.g. one causal study of universal childcare expansion of found
> this policy resulted in a rise of anxiety of children exposed to this new program of between 60 percent and 150 percent, and a decline in motor/social skills of between 8 percent and 20 percent.
See https://criticalscience.medium.com/on-the-science-of-daycare-4d1ab4c2efb4 for links to the supporting research on cortisol/childcare.
(Essex, 2002): https://www.sciencedirect.com/science/article/abs/pii/S0006322302015536
First child is more likely to have "high functioning" autism than subsequent children (yes, I know the autistic community doesn't like that term, but unless they can come up with a better one, I'll use it in inverted commas). One theory is that this could be due to elevated testosterone levels in the womb (which then decline for later children due to the fact that the poor woman has other children to look after, which tends to reduce testosterone levels). I would be very surprised if this wasn't associated in some way with the higher readership of ACX. Full disclosure: I'm autistic.
Could it be that younger siblings are more likely to mention the blog to their older brother than the other way around. Because when you're the younger one, you're always looking for things that the older one hasn't done before you. The older one doesn't feel the push. This could be debunked if you know how people came to the blog.
Older siblings are by definition older than younger siblings. If older people are more likely to read ACX (which seems pretty plausible) then that's going to be a major confounder.
I wonder if it is more subtle than just quantity of attention - it's quite exciting doing things for the first time with your oldest, teaching them things etc. but when you get to younger siblings, you feel you have already done whatever it is, and it is slightly boring so you don't bother quite as much - the novelty value has gone.
Even assuming an implausibly hard selection effect where all ACX readers have IQs and openness of at least 3SD above the mean, I can't get such an extreme skew towards first-borns. 64%, not 72%.
But it can certainly explain part of it. The first-born effects of IQ and openness are known, and known to be small (roughly 1/10th of an SD) but they show up more in the tails. If 1/10th is an underestimate (plausible for a few reasons), maybe we can go to 72%, but it's still an implausibly hard selection effect.
But what's the mechanism behind the IQ and openness effects? They don't show up in every culture (Botzet et al. 2021). The study major effects (Barclay & Myrskylä 2016) show up in Sweden, or I would have considered that perhaps in the US with the high cost of tertiary education, first borns are more likely to have their parents be able to pay for it.
> n <- 1e8
> bo <- rep(0:1, each = n/2)
> ops <- rnorm(n, 99, 14.98) + bo * 1.5
> iq <- 99 + 0.3 * (ops-100) + 0.95 * rnorm(n, 0, 14.98) + bo * 1.5
> cor(iq, ops)
[1] 0.3
> sd(iq)
[1] 15
> prop.table(table(bo))
bo
0 1
0.5 0.5
> sum(iq>145 & ops > 145)
[1] 2052
> prop.table(table(bo[iq>145 & ops > 145]))
0 1
0.36 0.64
> I additionally tried to compare two different types of social firstbornness - one where no older siblings lived in the house when you were growing up, and one where your parents had never parented another child. There weren’t many people discordant on these two measures (29 vs. 20 respectively), but for what it’s worth, the ratio was in favor of the first type.
I can't tell what this means. As far as I understand the terminology, the set of "people discordant on these two measures" unambiguously refers to every subject whose answers to question (1) and question (2) do not match. But that is a single set of people which cannot have population 29 and population 20. Who's in the group of 29? Who's in the group of 20?
> So for example, since the older sibling will always be smarter than the younger when they’re both young children
This claim can't pass a laugh test. How long did it take your little brother to be better than you at playing piano?
Great post, but I’ve got 3 kids and my immediate n=1 explanation didn’t really fit with your 2 suggestions. Seems to me it’s explained by the relationship dynamics of having a sibling but is NOT really to do with differentiation from each other. Young children who are 2nd siblings and relatively close in age to no. 1 seem to get a huge proportion of their social and intellectual development from the older sibling, regardless of gender and differentiation. I think that that close bond and dynamic reduces their drive to seek new sources of information (such as ACT) because the older sibling has such a strong influence in shaping their frameworks for viewing the world - even when they actively/ innately differentiate from the older sibling’s frameworks. In addition, the older sibling becomes accustomed to socializing the younger into their (older sibling’s) developing discourse. They are likely to feel rewarded/ fulfilled for this from the younger sibling’s receptiveness to taking in the info from them. This creates in aggregate a lasting disposition to seek new sources of info. Again, it’s easy to see that this may only play out within narrower samples, such as your readership, or with specific classes of info, but be lost at the general population/ broad context level.
My observation: The first child learns to be a boss by bossing around their parents first.
New parents want to be good parents and attend to their child, so they listen for what the child wants. They have time, attention and no experience at parenting at this point.
That first child can end up running the parents lives. And with that experience, any later children will be less experienced at being the boss and the parents will be more experiences at rearing children. But at the same time, the first child has already learned to dominate and doesn't like giving up that power. The second child might rebel and try to take a different path in opposition to the power of the older sibling, but a third or fourth child has to fit in some how. After all, the decision-makers, oldest child, parents and second sibling will make the rules.
Anyone care to comment on their observations of first child being the boss of the family?
As the technically ‘middle’ child of triplets (ten minute age gap solely due to birth weight) this birth order research always seemed a bit silly to me, but I suppose that’s mostly because of my personal unfamiliarity with the phenomenon of sibling age gaps.
From what I remember (being the 1st, and completing fitting the findings: I read ACT, I am in STEM while my brother choose a more artistic path), we should not look at parent investment or anything parent related (which fit well with parenting generally having little effect), but at direct relation between siblings. We formed a 2-member gang with my brother, with the eldest (me) the natural and not challengeable (at least until we were both past 17) leader. I think it fits my model of genetic>peer>parent in term of relative influence on every psychometric, when peers are siblings and later friends/schoolmates. Your siblings are part of your peers, the most important or even only one before 6yo...
The only thing I find quite strange in the data is that I expected a huge difference between same sex and opposite sex siblings: The brother sister dynamic is very different than between brothers (among sisters I do not know because I have no direct experience nor first hand observation among my friend's families)
It's often said that all of the original seven Mercury astronauts were first borns or only children and 14 of the next 16 American men into space were the same. But I don't see a link to a study.
As a Catholic Baby Boomer, my being a (rare) only child was a big deal when I was a kid in the 1960s. My friends assumed I got more presents on my birthday than they did (which I probably did). Adults were always telling me I was emotionally deprived by not having any siblings (which I probably was)
Now that only children are common, I never about them anymore.
Maybe for many younger siblings, if they do nerdy things at home, they get teased by their older sibling. And then "not being a nerd" might become part of their identity. But IQ other major life stats stay the same. This hypothesis would weakly predict that male dancers are much more likely to be older siblings.
It seems kind of strange that the focus is all on intelligence and academic achievement. The effect of birth order on readership of this blog (71/29) seems to be much stronger than for physics laureates (60/40) . While we might like to think that reading ACT is as good a proxy of intelligence as a physics Nobel, it suggests to me that it's a more specific personality trait that first-borns tend to have that correlates with attraction to a weird rationalist blog.
An interesting birth-order sports anecdote is Fernando Valenzuela, the Los Angeles Dodgers baseball pitcher who caused a sensation in the early 1980s. He was the youngest in a family of 12 in Mexico. He had one of the dumpier bodies you ever saw on a famous athlete, but was a baseball genius.
His older brothers were ardent baseball players too, but they had to go to work when still young. But Fernando was the adored baby of the family and was allowed to do nothing but play ball.
A possible overlooked confounder here is age. I'm 19 the oldest of 4. My younger siblings aren't at the age where they'd understand ACX.
As for your average 33 year old ACX reader you can suggest that many of your readers came on board in the Golden age of blogging ~10 years ago when their siblings were too young to come on board.
Is there some "recommended" way of sharing analyses? I'm curious about the the bio/social split, if I find something interesting I'd like to share.
I'm looking into it because I was a bit confused by Bucky's part about the biological vs social effects. If I get it right, the point of their selection (bio > 0, social = 0) is to filter people who had biological siblings at some point, but currently have none? I get that this would "isolate" the purely biological effects, but it also seems to introduce all kinds of other biases (it's not really representative of the general population) and additionally it doesn't even mean that there were no social siblings *at a previous time* in which it could have had an influence.
(btw the link to the CSV file in the old blog seems to be broken, excel file is fine)
I think it's explaining vs. imitating.
Of my three kids, each 21 months apart, the younger two strongly tend to do what their older siblings are doing. They learned early on that to imitate is usually a good choice, so they do it a lot and it serves them well. The oldest imitates adults of course, but not nearly as automatically, because she knows many things we do she cannot or is not allowed to do. What she does do, however, is explain things to her younger siblings and give them instructions. That's what she got from us and it's harder than imitation but I think she has learned to think in that way.
None of them are in school yet, but I expect the oldest will find explanation-heavy subjects like math and physics slightly more intuitive than imitation-heavy subjects like music and physical education, and maybe her younger siblings will tend to go the other way.
Of course the ratsphere is super into explanation and I would argue it grossly neglects imitation. When we try to persuade, we try to craft excellent explanations, rather than build shiny role models to champion beliefs we want others to share. But much, arguably most, of human learning in the general population happens through imitation. Especially on ethical matters.
Could sleep disturbance in infancy be an explanation? When you are the firstborn, your parents try very hard to avoid waking you up, and you enjoy uninterrupted sleep. When you have a toddler sibling, you get waken up all the time. If uninterrupted sleep is important for infant brain development, it would explain why the effect disappear as age gap increase (a 5 year old can keep quiet, a 2 year old can't), and it would explain the twins (twins wake each other up all the time).
Hypothesis: the ideal path for early brain development and interest in abstract ideas is:
- you have smart parents
- they spend 1-2 years with you at the center of their universe, talking to you to build vocab, reading to you, maybe fussing over your nutrition
- for the rest of your childhood they spend more time with your younger sibling(s) and leave you alone with lots of books
Supporting evidence: firstborn children are somewhat more likely to have poor vision
https://www.discovermagazine.com/planet-earth/why-more-firstborn-kids-need-glasses
Could there be some selection effect (at least for ACX readers)? Readership is smart and in an age range such that a smart older bro also reads ACX but the smart younger bro does cooler other stuff(?) Accelerating change of internet, older generations more similar than newer, I dunno.
I guess I'm an aberration. I wasn't around for Slate Star Codex, but I read this blog. I am the third of three siblings in order of birth. I know for certain that one of the others doesn't read this blog because he's dead, and I doubt the other one does because he's not a big blog reader and mostly not interested in even the wide variety of subject matter covered here (if you start covering the NFL and military matters a lot, he might notice).
I think that Caplan and others tend to overstate the results of the research he presents. I don't remember the effect sizes of the top of my head, but I think his data indicated that something like 1 SD "better" parenting led to 2-3 point increases in IQ. This is a much more modest effect than most people's intuition, but still significant, especially for tail outcomes.
The social sibling effect could easily raise the IQ of first borns by a couple points, which is going to lead to noticeably skewed ratios for the tails. If, among well educated parents, the average 1st-born IQ is 114 and 2nd-born is 110, then among IQ 140+ individuals who are 1st or 2nd born, 65% will be 1st born.
At least for Nobels, etc., I'm going to blindly guess it's the differentiation thing.
I know both me and my (younger) brother were absolutely determined we weren't going to do STEM related stuff because our dad was an accomplished programmer and adopting his profession in a world of infinite choice felt somehow medieval.
But it turns out genetics is strong. We're both garbage in our chosen careers because young folks stink at choosing careers. But we've both managed to fall into that kind of work later in life.
In a family that was more traditional (as I gather traditionally successful folks' families tend to be), I would have been pressured into my dad's profession (and inherited his business contacts) while my brother would have had to work something else out.
Do I think that's a recipe for general success in a typical family? Force your kid to do what you do? Absolutely not.
But when talking about people who perform at the very top of their fields, probably genetics and nurture both have to be moving in the same direction. And really you can only do that kind of intensive training with one kid, and probably you pick the first one.
There is a huge (n=4 million) paper showing birth order effect is real for homosexuality: https://www.tandfonline.com/doi/abs/10.1080/00224499.2021.197433
Also a new paper about IQ & birth order finds effect even controlling for family size (which is important because it was said family size-IQ relationship produces the IQ-BO statistical artefact):
https://journals.sagepub.com/doi/abs/10.1177/0146167212445911
These imply pre-natal environment IMHO
It seems like there is an assumption being smuggled in here, namely that “reading SSC is correlated more with intelligence than some other trait.”
What if that other trait is, say, conscientiousness, or being thing-vs-people oriented?
Like, what if older siblings are less likely to be as people oriented because they didn’t have someone a few years older than them as one of the most interesting, salient features of their environment?
I’d love to see if the “first borns are overweighted” thing is true even if you filter out people who put themselves on the autism spectrum. That’s the approach I’d be taking - I’d try and find subsets of the data where the trend dissappears.
FWIW in the 4th of 9.
This is only slightly related, but... Do first-borns tend to partner with first-borns? This is a trend I've noticed in my family and wondered about before. If there is some set of characteristics associated with being the first-born, it could be that people with a lot of those might be attracted to other people with a lot of those as well. This could explain not only my observation but also why these people clustered together as this blog's community.
With infinite resources, we could also survey a whole university, say, and see if people's chosen major has predictive power over their birth order. I think someone already mentioned this, but I get the feeling first-borns are more likely to be pressured into studying something traditional and "safe" than their younger siblings.
What about the likelihood of finding only children in your sample? If hypothesis 1 is true, we should observe more only children when controlling for the relevant variables (that is, considering that only children are possibly more likely to come from unmarried couples, short marriages, etc).
Some people commented on the possibility of a "mentoring effect" for first-born children. If only children aren't more likely to appear in the sample, then that hypothesis could be more likely.
I also think about other variables that are not related to intelligence. Like some readers mentioned, the likelihood of the older sibling finding more introspective hobbies. I also consider the likelihood of the younger sibling learning how to be more "charming" and social in order to get more attention and differentiate himself from the always older and more intelligent sibling.
"One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower? If it’s about having quality time alone with Mom, someone with a sibling one year younger than themselves only got one year of quality time; someone with a sibling five years younger got five years. But it looks like the birth order effect is stronger for someone with a one-year-age-gap sibling than a five-year one. Either the first year is very important, or I’m missing something."
Babies and toddlers are higher-maintenance. If the older sibling is already seven or eight when a new baby arrives, the baby obviously has more pressing needs, and the parents will in fact switch tracks to doting on the baby, possibly growing somewhat neglectful of the older sibling. Also, a much older sibling is old enough to, themself, help care for the baby, which will help smooth things over; a two-year-old is pretty useless (and sometimes actively harmful) around a newborn.
My explanation is that first children are required to take the lead on a whole host of situations where the siblings are involved. By taking the lead, out of necessity more often than not, the other children are relieved of that duty. That trains the younger children to be followers and the older children to be leaders. This explains why children a few years older create a stronger tendency, and also why after seven years it drops off - too little difference makes it less obvious who is in charge, while too much difference reduces interactions.
Why does this affect ACX readership? I think this blog interests people who are trying to figure out the world and make decisions about practical and moral effects. For someone who thinks that's important, there's a clear reason to follow the blog. For someone trained to let others do that work, then there's much less reason to follow a blog like this.
I’m an older sibling but I can’t imagine my younger brother, who has a higher IQ, earns more and is generally more successful, taking an interest in this blog. I tend to experiment a little more, have wider interests and deep dive into obscurity whereas he does the normal stuff very well
Wild. The one trait psychologists agree is known to be causally influenced by birth order (male homosexuality) is the one most accepted to be biologically and not socially caused?
" Firstborns get more quality time with their parents during the first few years of childhood."
I am puzzled. You seem to have an assumption that reading SSC makes firstborns better in some sense. But maybe it is something not-so-glorious that happens because the firstborns get more undivided attention of their parents: I can imagine the undivided attention makes them prone to navel-gazing and overestimating the extent their personal subjective experience and thoughts in general are super special and important and worth of loudly explaining to everyone around? Or, in other words, increased interest in philosophy (edit, and lets be realistic, strong political opinions)
The effect would be then naturally strongest in people who were the only child in the family. Eldest sibling has to learn to share when the siblings are born.
Does the data show there are more SSC readers who had no social siblings, compared to overall amount of them in the respective age cohorts?
EDIT. I didn't have siblings.
I'm really surprised that this (IMO very weak) conjecture is getting a pass:
"Given that readers of this blog are highly-educated (about 37% have masters or PhDs) and mostly in STEM (41% programmers of some sort), plausibly birth order affects something about intelligence, education, or STEM orientation"
I didn't take the survey. Did you ask if the siblings have advanced degrees or work in stem? Have you directly addressed the possibility that older siblings might just enjoy reading blogs more? Or as another user points out, be inclined to take surveys more? Or spend time on using the internet more? Or any number if other factors?
I guess I am the only woman and mom here and oldest daughter of a line of oldest daughters, and I had to smile a little because I never bullied my younger siblings: in fact in many times I was their mother and nurturer when I had to babysit for them. Now my sons.. well I see what you are talking about: though i always encourage them to get along: it was the second son who was the bully if any of that went on.. well gotta go.. yes. that is just our little story: circumstances vary.. have doctor's appts. today.
Anecdotal, but this makes complete sense when it comes to my childhood. Younger of 2, both pretty intelligent.
When at a young age my brother discovered e.g. that you can use strategy in games, he found that it let him win every game against me, so he focused on that discovery, and soon even won some games against my parents.
When at a young age I discovered that I could use strategy at games I found out that it does not matter, I never won a game not entirely on chance no matter what I did (because my brother of course by then was way better at strategy). So I stopped playing Risk, or Chess, or any games like that after a while, because what fun is it if you never win?
Sports was similar.
So my brother learned young that if you dedicate yourself to something, you can excel. Tends to produce a strong work ethic.
I learned young that what I do doesn't really change how things turn out.
You may not be surprised that his academic achievements surpass mine...
From my experience as a South Asian/East Indian immigrant (not necessarily high-income) is that among my first cousins on both sides, the oldest of the family is always the most 'traditionally successful' in levels of education, type of field, and income. This is regardless of gender or varying family income or significant life events.
Culturally, there's an idea that the oldest needs to make it for the family and the pressure is intense to do really well in school and everything else. I am not American either, so I can't imagine how much more formalized that gauntlet is with US-style admissions, etc. Perhaps there's something similar for Western families but less explicit and less tear-inducing.
in the developmental psych literature, does parental pressure itself do better than parental investment in the form of Advanced Einstein baby toys or reading books? Its hard to disentangle the two, of course both nature and nurture-wise.
I think some consideration to the ideas outlined in "Deep Nutrition" a book by Dr. Cate Shanahan which talks a great deal about the findings made by Dr. Weston Price should be included. The idea is that nutrition plays an enormous role in physical health and intelligence. Their assertion is that inadequate birth spacing (less than the 4 years they consider ideal) means that the mother is nutritionally deficient which is then passed on to the child creating less than ideal conditions for proper growth and maturation. I am by no means an expert, but I think this merits discussion.
It's fascinating to see this effect in the data - it's *quite* clear in my own life. I'm the oldest, a lifelong nerd. One of my brothers is two years younger and always rejected academic stuff - not necessarily less smart, just much less interested in it. Then my other brother is several years younger than both of us, and pretty nerdy. Point for point reflective of what we see in this data.
A major difference that I don't see in the comments below is that first-borns with reasonably small age gaps are always a bit further along than their siblings. If you're a parent and you want to teach something, it is very likely the first-born who is most able to learn it. If an opportunity comes up and you're trying to figure out which of your children is best positioned to take it, that as well is most likely to be the first-born.
"Given that readers of this blog are highly-educated (about 37% have masters or PhDs) and mostly in STEM (41% programmers of some sort), plausibly birth order affects something about intelligence, education, or STEM orientation"
Well, if I didn't have Imposter Syndrome beforehand, I do now! Should I bask in the reflected radiance from the smart and successful, or ask 'what the hell am I doing here?' 😁
At least I *am* a firstborn so that's legit!
Is it possible that first siblings are more likely to contend with mental disorders, and subscribe to this blog for the psychiatric content?
"This was surprising, because at the time lots of studies had shown there weren’t really birth order effects (that is, firstborn siblings had no major personality differences compared to laterborns)"
What were those studies? Do they seem to have been decent work?
Has anyone checked the data for siblings _raised separately_?
The question that I'm really interested in: where are the younger siblings filling out surveys? Is there another blogger (or vlogger) that has that audience? I'd like to find them.
This paper supports the social over the biological explanation for birth order effects, using people whose sibling died early to differentiate the two explanations: https://www.science.org/doi/full/10.1126/science.1141493?casa_token=D9rI2H8xO1QAAAAA%3A_a1enql0bllAir1AhNMzaQUmWhg6kdrHG4r44IhYxecA-Rga2uPq51EflwvpTKKRy-aXnhanT7l0Iw
Another reason your "trollish" concern about twin studies doesn't get us out of the problem is that adoption studies tend to find the same results as twin studies re the low effect of shared environment.
> Followup research by Less Wrong user “Bucky” determined that the effect fell off with age gaps; the closer in age you are to your sibling, the stronger an effect birth order has.
Some supporting anecdata: I'm the firstborn in a family of six with three triplet younger brothers who are two years younger than myself. Interestingly, the differences between my three fraternal triplet younger brothers are stronger than those between the three of them and myself, and those differences really do line up with the observations made in this essay by multiple metrics.
If I were to identify a cause, it might stem from my parents consistently treating the elder among us as "more mature" and frequently giving us more responsibilities while doing the opposite with the younger, going as far as actively taking away responsibilities. (Yes, they did this even though my three brothers were pulled out of the C-section mere moments apart.) As we grew, we'd reinforce this dynamic among ourselves, often as justification for why the elder deserved certain privileges or why the younger could neglect certain duties. Without a doubt, this sort of treatment had significant effects on all facets of our psychological development, both cognitive and emotional.
I have noticed that the youngest sibling tends to be the "coolest" - i.e. more popular, social, etc. Possibly because they have an older sibling to teach them, hence the stereotype of the cool kid who knows about sex and alcohol because of his older brother. Others have already mentioned differences in parenting, which could contribute to this as well (parents are more lax with rules as # of kids increases -> younger kid spends more time partying and less time studying). Not sure if this is a real effect but perhaps the birth order effects noted here are not so much about older siblings being smarter or more STEM oriented but their younger siblings being less so.
Older siblings are also older. Maybe their younger siblings just have not yet discovered ACT but they will when they come of age.
I don't know if you account for half-siblings here and whether this is on the maternal or paternal side.
Maybe scenarios with a biological sibling but not a social sibling are disproportionately of type: dad has a child from a previous relationship but doesn't have custody, has second child in a subsequent relationship.
Dude, isn't the simple and obvious explanation that the older sibling develops a leadership role and therefore has to be more serious and intellectually-inclined? As opposed to comedy or sports?
I'm not sure what the biases in this kind of analysis are, but as a control group I'd be happy to see it done on other blog readerships or other self-selected groups.
Two of my children are quite close in age. They are close enough when they were small it was easy for them to forget that there was a significant age gap. So the older one was convinced for years that he was really smart; and the younger one was convinced for years that he was an idiot -- when actually they're about the same. Also yeah, they get the "oh, reading big science book's is something my older brother does" factor too.
One hypothesis I though of was that. In the ancestral environment, there was a need for different types of skills and personalities, but by the time someone was old enough to see for themselves which personality types the tribe is short of, it is too late for the brain to make the necessary adjustments. One way around this is for children, in early childhood development, to look around and see what personality types and skills surround them, and then pick complementary skills. Since most young children spend most of their time with siblings, this would create the effect. This would explain why sex doesn’t seem to matter, and why age gap does— children spend more time with siblings closer in age.
Source: oldest in a family of four, each of my siblings has a personality strong in the thing that the sibling one above them is weakest in.
Scott could see if this is true by, in the next survey, asking people how much time they spent with their family in early development, versus, say, a day care, and then seeing if more time = stronger effect.
The ideas I see are interesting in terms of why older siblings would seem smarter or more interested in STEM... but in general I think it would be useful to ground them back to how exactly they would increase their chance of reading this particular blog. This blog ends up having a STEM stereotype, but actually the content is pretty varied: the biographies of dictators, cost disease, drug discovery and pricing, "Untitled", "You are still crying Wolf", Unsong-adjacent and Fifty Swifties...
Another issue is that maybe older siblings are more interested in filling in surveys? There are older-sibling stereotypes that they have an inflated sense of self-importance; and stereotypes that they have an inflated sense of civic responsibility -- if either were true then that could change it?
I think probably the biggest selection factor on your blog is an attention span? The style of burying the lede deep into the twentieth sub-paragraph (which I'm not knocking -- I enjoy) is the opposite of what pretty much everyone else does -- it is the opposite of clickbait, and means that you normally have to read a few paragraphs in before the hook -- and I have always imagined this is one of the reasons the comment section here is so good. Again, it would make sense to me that older siblings have a longer attention span. If the first child has two parents to entertain them. The second child has two parents and an older sibling to entertain them.
I was wondering about networking effects. I know about this site from word-of-mouth. How do other people generally know about it? Do older siblings have larger networks? What I generally observe in families I know is that older siblings are often closer to the parents' generation than younger siblings, who seem more distant socially somehow -- so in this sense, I guess they have a network boost. I probably get send more links by my parents, aunts and uncles, than a younger sibling of mine would -- maybe I should ask. Again anecdotally, but it seems to me that connections travel up through older siblings more often than down through younger siblings. Maybe it's a seniority thing: it seems cool and interesting to get to know your friends' older siblings -- they're always at the next stage of life; but maybe not so much their younger siblings?
My immediate thought is that second borns grow up in a complex social situation with peers. That may require them to develop more complex social skills/pay more attention to interpersonal situations. That may skew later career choice away from STEM fields. (More specifically some non stem fields gain attraction while stem stays the same, losing relative attraction)
I'm surprised Scott missed this seminal paper by Raj Chetty from Harvard- https://academic.oup.com/qje/article/126/4/1593/1923939
Even Bryan Caplan concedes that the signal that this paper picks up is sound, and weakens Caplan's hypothesis somewhat.
It says that although parental income, environment at home, etc does not affect future earnings as much, one thing that invariably does affect future earnings and achievement is the quality of kindergarten training. I suspect that it is this effect that is even stronger at younger ages (say the first year of the child's life), which is what Scott is picking up in this survey.
First-born children face more pressure from their parents to do something practical and conventional with their lives.
Meanwhile, the key demographic of readers of this blog is "Frustrated philosophers" -- people who wanted to study philosophy at university but wound up doing computers instead.
Stupid question: How do you control for the effect of older-born siblings *being older*, and thus having had more opportunity to become ACX readers?
It seems to me that ACX doesn't select for intelligence, it selects for a certain kind of intelligence and temperament. Wide interests (I think of that as fannish), a tendency to want to look at things from the outside, and at least some tolerance for liberal/anti-progressive politics.
Do venues which have smart people but differ on the other factors still tend to have a lot of first-borns?
Unless you randomly selected people to answer the survey, could there be a confounding factor that first borns tend to answer surveys and such?
Being the 3d of 3, my opinion wasn't worth much at the dinner table. And I don't rate Amazon products or give Yelp reviews. Could being higher up in birth order make a person more likely to answer ? That would tip the balance in their favor if they tend to self select
i'm the youngest with a 9 year gap to the closest sibling, my siblings were basically like extra parents/ guardians.
I think a good comparison for more research would be to compare with only children. To disentangle if it's to do with 'lots of attention when young' vs 'responsible for someone younger than you' vs 'most competent person around your age in your house' among other things.
Having an older sibling close enough in age helps you develop better theory of mind earlier, which makes you grow up less nerdy, and you are less likely to end up becoming a programmer who reads acx
I didn't read all the comments so this was probably raised before but since you are looking for differences in whether someone reads your blog or not one obvious question to ask is how someone came to read the blog. Specifically I read this blog because it was recommended by my older brother. Perhaps there is some asymmetry in recommendations from older to younger siblings and vice versa. (Although that would mean my case goes against the trend.)
(P.S. I did not answer the survey and I am guessing my older brother didn't either.)
Maybe the first borns are just higher variance so they show up more in more selective extreme groups? And maybe that's because the parents pay consistently more attention to the younger one when both have already been born? Or because of something related to the dynamics of having and older / younger brother, like bullying, competition.. or the younger one having to follow the steps of the older one, inheriting the toys that the older one chose and liked, etc.
I don't think it's regression to the mean where people have a second child only when the first one turned out a decent experience, because I think most people that have a child have more than one, right?
OK, my theory from last time around:
It's not IQ or general smartness that is being selected for. What sets this group (and the Nobel-physicist group, and the great-mathematician group, and maybe the Harvard-philosopher group) apart, as I mention in my reply to Nancy Lebovitz, is that we are that ultra-nerdy rationalists, very often STEM nerds in particular, and we like to Think about Things. Which, really, is kind of weird.
A firstborn child, or a social-firstborn or a younger child with a large age gap, spends the first years of its life trying to comprehend a world full of Weird Interesting Things. Some of those things are called "grown-ups", which are technically "people" but from a toddler's POV they're a completely different order of being. They're weird interesting things.
A (not too much) younger child, spends the first years of its life in close company with at least one other *person*, a person not too different from themselves. And if there's a Weird Interesting Thing that they need to understand, maybe the best way to do that is to learn from that other person.
So maybe the firstborn child is more likely to adopt a Thinking About Things outlook on life, rather than the much more common Understanding People outlook. They're not *smarter*, they just use it differently. And really, even most of the firstborns will wind up in the Understanding People group; that's just how people are wired. But if you're selecting three-sigma outliers in Thinking about Things, you're selecting for firstborns.
This seems to me at least as good a fit to the observed data as any other hypothesis, and better than most.
Well, the obvious hypothesis that comes to my mind is parental expectations. One thing that is very obvious about parents is how much they chill out between Child #1 and Child #N, for N > 2. For the first (or, worse, only) child, parents' expectations are sky-high.
My kid is going to be some combination of Einstein, Mother Theresa, and Winston Churchill. Since he needs to get a PhD from Stanford by age 25, he needs to graduate from Harvard at 20, which means he needs to go some super-competitive magnet high-school after skipping a grade or two in a superb private elementary school....so damn it we better get cracking at getting him into that enrichment pre-school that has only people with PhDs changing diapers -- he's already 3 years old for god's sake! And stop giving him the regular mashed peas, he needs the choline-vitamin E-probiotic fortified 100% organic mashed peas harvested from the slopes of Vesuvius by the lineal descendants of Aristotle. You want him to turn out ordinary??
Comes child #2 or #3 and it's like hey honey little Billy was eating laundry soap again and he looks unhappy, could you maybe get him some water to wash the taste out?
I remember Gilovich talking about birth order effects in his Behavioral psychology class. He seemed pretty convinced. He liked the explanation that birth order effects stem from having to teach the younger sibling things and that you can see the same effect with only children in the US whose parent's first language is not English. They had to teach their parents.
Could the answer be hiding in plain sight? If you were to start club called the "Older Than 10 Club", wouldn't you expect the membership to be skewed towards older siblings? Either:
a) if both siblings belong to the club, they don't bias the sample
b) if neither sibling belongs to the club, then they don't appear in the data
c) if only one sibling belongs to the club, the older one is more likely to be a member, on account of the fact that there are more people older than 10 than there are people younger than 10.
Maybe this blog is most attractive to people who are older than a certain age, on average, and that accounts for the bias?
"The current scientific consensus is that parental investment in the early years of life doesn’t really increase IQ or educational attainment .. This research challenges those assumptions. If it’s right, the difference in parental attention between an only child and a child with siblings seems to have noticeable effects later in life."
The implication here is that birth order -> IQ -> SSC reading. As a first-born SSC reader I like that theory, but I can think of some more plausible relationships.
Maybe first born have had less socialization and are more likely to enjoy solitary interests?
I can propose one more hypothesis. Firstborn are not more intelligent, they try harder. They grown up being more intelligent than their siblings, their "intelligence" is a part of their self-image. Yeah, now I'm talking about myself. And I'm a pretty severe case of it, up to panic attacks when I didn't manage to hold an image of a very smart person. People really asked me "what happened? why you gone all white?". Yeah, I'm talking now about me, not about all firstborns, but I'm pretty sure that one of two big reasons of my condition is me being firstborn. I was responsible for me and my brother all the time. If my brother fall into a river, than I was asked "how it happened, and why I didn't prevented it". It was like my brother fall victim to my stupidity. It was not literally said, but "you need to be smarter" was one of phrases I heard a lot of time being a kid and in my teens. I rebelled at 14-15 against this responsibility. It is a different story, but note that I rebelled against responsibility, not against me being smarter. It took me 20 more years to start fighting my self-image of an intelligent person.
So, my hypothesis is: firstborns try harder to seem intelligent, they develop the whole strategies how to be (or to seem) more intelligent than others. These strategies include "tactic" reactions to stimuli, allowing to hide their "stupidity" (like if I did not understand what happens, I give others a possibility to ask "what happens" or to say/do something that might help me to understand what happens, and I would try hard to be unnoticed). But it doesn't stop here, firstborns learn to be curious. In an academic sense of the world. To learn what other think about some problem is nice, when you forced to talk about this problem, you could make a reference to a few sources, lay out a few different opinions and then maybe even to verbalize your own thoughts on the topic. Or in other company it is better to "plagiarize": to express some opinions without references.
I told, that I'm a severe case, and I really do not know how bad it goes in minds of other firstborns. But what I'm trying to say, that it is not just "I try harder", it is how I live, it is who am I. I read ACE not because I need more smart thoughts cached, I read because it is fun. But it is fun, because I learned as a kid, that intelligence is my inherent psychological trait, and as a teenager I found ways to match to this trait. It is just conditioning.
I cannot say, I know, how to prove it. I'd try to get an operational definition for my condition, to get a way to measure it by looking at behavior. Then to use it on many people, and to study those who hit high scores on the condition -- let them fill a lot of questionnaires, find all the correlations. Then probably we could find an easy to measure trait which is highly correlated with the condition. And then we might find it in the data gathered here.
Though, there was mentioned psychological research of siblings? Did they tried to give some unsolvable task to siblings, while measuring time they spent on it before giving up? Or to place them in unexpected difficult situations, while measuring "smartness" of their way to deal with it. (I called it "smartness", but really it is not about smartness per se, it is about how they manage to look intelligent people.) It may be tricky to operationalize, but I believe it is possible.
Two things stuck with me:
1) if I understand Becky's comment correctly, the dataset contains more people with zero biological and some social siblings than the other way around, which is surprising to me and may indicate an important selection effect.
2) the whole essay seems to use "being a reader of ACX" as equivalent to "being more intelligent than the average in general", which doesn't sound justified by mere correlation. The fact that ACX readers are more likely to be highly-educated and also firstborns doesn't automatically mean that firstborns are smarter in general.
Most obvious answer I can think of is seniority dynamics. Confidence and success breeds further confidence and success, and the oldest sibling is always at the top of the hierarchy. This fits with the huge drop off we see between Sibling 1 and Sibling 2, and the much smaller effect when going from Sibling 2 onward.
I don't think parents have much to do with it. Kids get most of their social input from peers, not adults, and siblings - especially those close in age - are the most important peers of all.
"One problem with (1) - wouldn’t you expect smaller effects as age gaps get lower?"
Yes, the first year is important, but also consider school/preschool: Age gaps over a certain number of years basically give the second child an experience more like that of a first child, since the first child is out of the house or at least more independent.
I thought it was interesting that the decline of the ottoman empire began within a generation after they switched from primogeniture to agnatic seniority.
As a first born with good general success compared to my siblings, the largest difference today is our openness to experience, and willingness to try to fix a problem. They are just as smart as me usually.
I suspect the openness part could be partially due to me not having much help solving problems when I was little, I had to do it myself, or it wouldn't happen (my parents weren't great at helping) whereas my siblings could always get assistance from an older person rather than do it themselves. Having good initiative on learning and doing pays compounding returns.
I'm doubtful parenting has anything to do with this, likewise infancy, as the effect gradually reduces over 10 years. To me the most plausible explanation is firstborns' requirement to figure out a lot of things on their own. This would inculcate increased amounts of "seeking for the truth"; trying to figure out how the world works. The closer in age a sibling is the easier it is for them to learn by example of the older sibling or to just be directly taught by the elder. A 15 year old would struggle to teach a 9 year old relevant things that the parents couldn't teach just as well.
Supports: This is a social explanation, not biologically dependent. It explains the smooth reversion to the mean rather than dropping off suddenly at some point (as an infancy based explanation might suppose).
Problems: I would expect a small amount of gender disjunction but that seems not to appear in the analysis.
Tests: The effect should decline in more communally raised children, where they have very close relationships with children their age (or one year older).
Disclaimer: I am an eldest with 3 younger siblings (none of who read SSC/ACX).
Here's what I think of the first born. Enneagram 8.
Challenger
Basic Fear: Being controlled or violated by others.
Basic Desire: To determine their own course in life. To protect themselves.
Eights want to stand alone, to have power over their lives, and to achieve their goals. They are extremely driven, resourceful, and propelled towards their vision and purpose. They don’t want to feel indebted to anyone, emotionally vulnerable, or in any way dependent. Autonomy and freedom are vital to their happiness; the only problem is that they may defy being vulnerable so much that they miss out on fulfilling relationships in the process. These types crave a sense of intensity in their lives. Whether they’re race-car driving or starting their own business, they enjoy proving naysayers wrong and testing their abilities and strengths.
In childhood, Eights felt that they had to grow up quickly. Early on they felt that they were in some way responsible for the welfare of their family. There was no time or safe space for vulnerability – they had to be strong. Survival issues were at the forefront of their mind. Being gentle, giving, emotionally open – these typical INFJ characteristics were probably repressed because it didn’t feel safe. In some way they felt there was a risk of rejection, betrayal, or pain if they let their guard down. They developed a tough, independent, hardened demeanor as a way of dealing with their pain.
Eights are in the Gut/Instinct triad of the Enneagram. This means that they have underlying issues with anger. While Nines avoid their anger and Ones repress it, Eights express their anger. They like straight-talk and directness and tend to be assertive themselves. When threatened or controlled they can become explosive and intimidating. They feel very defiant of any institution that tries to control them – and they may make life choices simply to rebel against that institution. Whether it’s dropping out of school because the teachers were too controlling, marrying someone a parent doesn’t like, or driving faster than the speed limit on a bad day.
Unhealthy Eights Can Be: Destructive, Vengeful, High-Tempered, Rejecting, Private, Hardened, Authoritative, Bossy, and/or Confrontational.
Average Eights Can Be: Resourceful, Businesslike, Competitive, Boastful, Willful, Proud, Bad-tempered, Hard-Working, Independent, Visionary, and/or Determined.
Healthy Eights Can Be: Courageous, Heroic, Forgiving, Energetic, Independent, Action-Oriented, Resourceful, Direct, Protective, Generous, Inspiring, Strategic, Decisive, Self-Confident, and/or Authentic.
The results paint a really interesting “secret cultural wisdom” argument for primogeniture
I wonder if a similar effect can be found for first grandchilds. I am the first grandchild for both my paternal and maternal grandparents.
Sincerely believe that its the forced leadership. In group play, (and many other situations) the older sibling has to take to the lead. This means generating play ideas, structuring play, and reinforcing play rules. This would explain why the effect is stronger when the gap is closer, and how it could be social without necessarily being based on parental involvement. I think that this could bias some personalities towards valuing things like intelligence and independent thought without actually being smarter (valuing intelligence might make you more likely to invest in your own, but wouldn't necessarily bump you out of your bracket). You might see some boosts in creativity from early practice - but the overall thing that gets affected is not the underlying skill but the perception of which skills are desirable. That would mean that your strongest sibling-order-effects would be in preferences - characters you relate too, ideas that draw you in, or blogs you read.
Father of two kids here, so my sample size is 1. However, I suspect that the cause is "bossiness". In my family, the younger sibling is the bookworm; she loves to read, and is by far the more STEM inclined. But the elder sibling absolutely loves to "mother" her, and always wants to be in charge of whatever games they play, even though the age difference is only 1.5 years. As parents, we have to constantly work to make sure that the younger sibling has a say in things. I would hypothesize that 10+ years of unintentional "leadership training", or conversely, "follower training", might make a significant difference.
Maybe older siblings are poorly socialized due to having no older siblings, thus more likely to be "on the autistic spectrum", thus more likely to subscribe to AC10.
If my first kid is smart I am more likely to have another one. Add some random distribution of intelligence between kids and regression to the mean and we have an explanation.
Another possible mechanism, which is biological, but not genetic, is the potential effect of early illness. Just anecdotally, my first child wasn't sick for the first year of their life due to lack of exposure to other kids, but I fully expect my second to be sick much earlier due to picking up things from the older one. I'd expect this to attenuate over time as the first is more able fight off infections before they spread to others.
If this is true, I'd expect this effect to vary based on when/whether childcare like daycare is used (and what type). Also does this vary over time? Were there birth order effects in the early 1900s, for example? How do they vary across countries?
One (anecdotal, unscientific) observation I have made is that boys with older brothers (this one is sex specific) tend to have more tenacity than those without. I attibute this to the type of rough play the boys tend to get into (much to their mothers' chargrim) wrestling, stick fighting, etc. The younger brother will almost always lose such games and yet is expected to play on anyway to grow stronger and hope for the sweet moments when he can catch the older brother off guard.
I would love it if someone could suggest a way to test this theory or even better actually test it.(The hard part I believe it's coming up with a suitable metric for "tenacity", I am highly skeptical of anything involving self reports)