No support for birth order effects on personality from the GSS

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In researching for a review of The Nurture Assumption, I read over the debate between Harris and Sulloway over birth order effects on personality. Sulloway’s thesis, explained in Born to Rebel, is that last-born children have more rebellious, agreeable, and open-minded/liberal personalities, and that this manifests itself in history with revolutions spearheaded by last-borns. This runs in contrast to Harris’s theory that the family environment has no lasting impact on personality, so she spends a good deal of time in her books and articles critiquing it.

The whole debate makes my head dizzy. A seemingly simple empirical question has produced years of arguing over methodology. I’m not going to go over the tedious back and forth here, except to say that you can see what both sides have to say with a Google search.

Large, controlled studies have not been kind to Sulloway’s thesis. Freese, Powell, and Steelman (1999) looked for a relationship between birth order (controlled for family size) and a variety of political measures on the nationally representative General Social Survey (GSS). They found no significant associations, contrary to Sulloway’s predictions.

I decided to look at the GSS myself, this time to see whether questions that tapped into personality characteristics outside of politics showed any relationship with birth order (SIBORDER), when sibship size (SIBS) was controlled for. I excluded only children. I used the Multiple Regressions feature on the Berkeley SDA tool. I found no significant associations between birth order and any of the four variables I looked at:


  • MEMLIT (proxy for openness/creativity)- “Here is a list of various organizations. Could you tell me whether or not you are a member of each type? m. Literary, art, discussion or study groups”

  • TRUST (proxy for agreeableness) – “Generally speaking, would you say that most people can be trusted or that you can’t be too careful in life?”

  • WORLD4 (proxy for agreeableness) – “People have different images of the world and human nature. We’d like to know the kinds of images you have. Here is a card with sets of contrasting images. On a scale of 1-7 where would you place your image of the world and human nature between the two contrasting images? 1. Human nature is basically good. 7. Human nature is fundamentally perverse and corrupt.”

  • OBEYLAW (proxy for rebelliousness) – “In general, would you say that people should obey the law without exception, or are there exceptional occasions on which people should follow their consciences even if it means breaking the law?”
I wouldn’t say that we should write off the idea of birth order influences on personality and intelligence, only that we should be very skeptical of them. To the extent that they do exist, they’re probably not very significant.

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6 Comments

  1. The only possible advantages I can see in birth order are that the first-born likely gets more attention, but it’s inexperienced attention, whereas later born (specifically last born) get both more attention (they are the last to leave home) and more experienced attention. 
     
    It’s the middle child who gets either the best or worst of both worlds… says the whiny middle child. 
     
    Best illustrated by the fact that when we left for college, my older brother got a VISA card, my younger sister a MasterCard, and I got a gas card. 
     
    We are all over the age of 50 now and still all incredibly spoiled. We were all the 1st child in some ways as there is 7 years between me and either of my siblings. 
     
    Even anecdotal evidence doesn’t show much support, eh?

  2. The only possible advantages I can see in birth order are that the first-born likely gets more attention, 
     
    Well, there is also the possibility of biological maternal effects. Why must we assume that a woman’s body responds in exactly the same manner for each successive child?  
     
    Possibly related: Effect of birth order on sexual orientation. 
     
    Apparently, some people have failed to replicate the results, while (several) others have succeeded. Some say the effect is biological (adopted sibs have no effect), others disagree. Caveat lector. 
     
    This runs in contrast to Harris’s theory that the family environment has no lasting impact on personality,  
     
    Not necessarily, if the effect is a maternal (i.e. biological) effect.

  3. Donna, 
     
    A lot of people provide anecdotal support for birth order effects because they observe that it matters in the family setting (which is really the main time that most people see their family). Obviously the bigger siblings get to beat up the younger ones, the younger ones can whine to mom, etc and that matter. The important research question is whether birth order has a lasting effect outside of the family by the time people grow up. 
     
    toto, 
     
    very interesting line of research. indeed, i would find it strange if there weren’t all types of prenatal differences relevant to psychological development associated with birth order.

  4. It seems like it might be worthwhile to control for actual families. 
     
    Rather than try to say ‘first children are more open than average’, look at ‘first children are more open than their siblings, on average’

  5. Granite26, 
     
    Harris addresses that in an online essay
    Sulloway’s second criticism of self-report tests is that studies that do not directly compare siblings within the same family might produce spurious results due to “confounding effects associated with differences between families” (1999, p. 192). This is true. However, some of the researchers who used self-report questionnaires (Freese, Powell, & Steelman, 1999; Hauser, Kuo, & Cartmill, 1997) have performed within-family analyses, directly comparing the responses of siblings in the same family, and nonetheless failed to find significant birth order effects.Also, I would note that you have to be extra careful with studies that compare family members. If you’re asking them stuff like “are you more outgoing than your brother”, then you’re not measuring the outside-the-home personality that we’re interested in, but rather how they act when they’re around each other (where no one would deny systematic birth order effects).

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