


Some researchers have theorized that firstborns are more successful than younger children (lastborns). Though they don’t have a leg up on all potential measures of success, 23andMe’s firstborns are more educated than lastborns. Even controlling for age, sex, and correcting for multiple tests (as we did for all the findings reported here), firstborns reported greater educational attainment than lastborns. We can’t say that this fully confirms the idea that firstborns are more successful, as they did not report higher incomes or higher subjective socioeconomic status.

Personality theorists have also postulated that firstborns are more conscientious, more socially dominant, less agreeable, and less open to new ideas than lastborns. In actuality, we found that firstborns are more full of ideas, but less altruistic than lastborns. These results are consistent with some but not all of the existing, but controversial, research on firstborn children’s personalities. While altruism is a component of agreeableness, and therefore might seem to support the theory, firstborns did not differ significantly in overall agreeableness, just altruism. Why might this be? We’re just not sure. Perhaps lastborns have to learn to share from an earlier age than do firstborns. Have a theory? Leave it in the comments below.

Finally, firstborns are more likely to have had chicken pox or mumps. This was really interesting and completely unexpected. It’s possible that having an older sibling might reduce your chance of contracting certain childhood diseases.

As an aside, one of the red herrings for this last question was that firstborns are more likely to smoke. In fact, the opposite was true. Lastborns were significantly more likely to have smoked than firstborns. About a third of lastborns had smoked regularly at some point in their life, compared to roughly a quarter of firstborns.

Have your own theories about birth order effects? Leave a comment below!

  • As firstborn, my childhood experience is that I did not feel that I got anything but trouble and undesired responsibilities from having siblings after me. Therefore I find only natural that firstborns can be less altruist because they learn to consider others as competitors and a burden and not any source of corresponding benefits. I’d say that a firstborn is a lone child that got unlucky, specially if there are many siblings after him or her. Firstborn with siblings are demanded to behave almost like adults (give example, take care of younger siblings) at a too young age and I can only think as normal that they instinctively reject that by becoming less sociable and more selfish (to some extent and depending on individual cases, of course).

    Probably younger siblings have the double problem of having to learn to agree or concede to older ones and also reckoning that they actually get benefits from the efforts, sometimes reluctant, of their elder siblings, as pioneers (bending the will of the parents with their rebellion, who almost invariably are softer with the younger ones), teachers and caregivers.

  • Tara

    As the eldest child with two younger siblings I have found myself to be far more independant and responsible than my siblings in many ways. This is not always a good thing for me because most of the time I become overly independant and quite reserved along with it. I sort of feel like I have to be fully responsible about everything and am also very analytical.

    From experience I can say that the eldest child almost always develops maturity much earlier in their life compared to their younger siblings. This could be due to having to look after siblings or being expected by my parents to be a good role model. It also comes down to being the one who does nearly EVERYTHING first. School, puberty, getting a job etc.

  • Claudia

    Here’s something I never could quite decide in respect to those studies:
    if one of our parents already has an older child, but our other parent doesn’t, and we’ve never lived with that older child, should we consider ourselves more of a “firstborn” than “lastborn”, or?

  • Crystal

    I’m the youngest of three. I currently have the highest education of everyone in my family on both sides for generations. I likely was more experimental as a child, but more career oriented at the same time. I’ve been as independent as possible -never accepting money from my parents and always trying to manage/succeed on my own accord. I feel that these studies/surveys may be biased mostly by who takes them. Most 1st born are watched more carefully, but that also means they get more attention and in many cases they get to experience more activities as a child. They also tend to get the newest things as they are the first to need them. They do take on responsibility at a young age watching younger siblings, but I think all children can get that experience and those attributes if the parents raise them with chores or some activity that is weighed in on needing them. First borns also tend to marry first, maybe due to age or it might be a lack of independence after going through so much. Honestly, I think life lessons and experience overall weigh in much more than order of birth.

  • Crystal

    lol also as the youngest you get blamed for EVERYTHING… I learned to just accept that regardless of accuracy =)

  • Tanya

    I’m the middle child & female. I have a younger & older brother. And they are both equally successful & both equally responsible. Yet my younger brother is more open-minded. My older brother is a bit more conservative. But my older brother definitely takes on & accepts more responsibility as in a traditional sense.

  • Jim

    “firstborns reported greater educational attainment than lastborns”

    Yea, because most parents can only afford to send one to college. After that, the funds are gone.

  • Helen Kimbrough

    I only want to say I found this very interesting. In looking back at the family I grew up in , My own family and others I have known . This analogy sounds very accurate. My sister and children in my own family consisted of my older sister and oldest sister in my own family and the older does seem to feel greater responsibility and pressure and to be more outgoing . Interesting how that might prepare the older for other accomplishments that advanced living requires ; and changes that might take place in the younger of siblings as they grow older.

  • Skeptic

    With respect to chicken pox and mumps, presumably the data crunchers were smart enough to control for families whose oldest and youngest siblings bridged the development of vaccines for these diseases. Otherwise the results are hardly remarkable. I was born before there were vaccines for either virus, so of course I had the diseases (chicken pox when I was in grad school!), but those born in later decades are quite unlikely to have had them.

    Another confounding effect is that these surveys rely on recall, which is notoriously inaccurate. If you believe you had one of these illnesses as a young child you are likely relying on your parents’ recall. It stands to reason that parents are more likely to remember a first-born getting mumps or chicken pox, because it was their first experience in caring for a child with these physically obvious symptoms. Things may start to blur with the third and later child . . .

    Basic survey design issues.

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