Sibling Relationships and Why We Can't Blame It On Birth Order Anymore

   By drodriguez  Jul 27, 2015

If you’ve ever finished a thought by saying, “well…that’s probably because I am the first born, middle child, or baby of the family” than you’ll be interested to hear that ideas about birth order and how they shape our personality development may actually mean very little in the long run. A new study suggests that the order in which you are born may not really have much of an affect on the way you develop as an adult.

Forbes reports about the largest study of birth order ever conducted that suggests everything we’ve been told about first borns and later born siblings is incorrect. Researchers studied about 377,000 high school aged students to see how borth order affected their intelligence and personality development.

The study, published in the Journal of Research in Personality did find that first-borns tend to score slightly higher on IQ tests than their siblings, but only by about 1 point. The first-borns also tend to be slightly more extroverted, conscientious and agreeable than their siblings but researchers deemed the difference to be “infinitesimally small”.

Co-author of the study Brent Roberts explains how the slight variances in personality would be undetectable to the naked eye. He says, “In some cases, if a drug saves 10 out of 10,000 lives, for example, small effects can be profound. But in terms of personality traits and how you rate them, a .02 correlation doesn’t get you anything of note. You are not going to be able to see it with the naked eye. You’re not going to be able to sit two people down next to each other and see the differences between them. It’s not noticeable by anybody.”

Researchers hope the current study will trump the data that has been collected in the past regarding birth order because previous studies have used much smaller sample sizes deeming them more unreliable. The study’s other co-author Rodica Damian hopes that the current findings will help parents understand that they shouldn’t rely on birth order to make parenting decisions or label their kids. She says, “The message of this study is that birth order probably should not influence your parenting, because it’s not meaningfully related to your kid’s personality or IQ.”

What do you think of the latest study suggesting birth order has very little to do with personality development and intelligence?

Do you tend to rely on past ideas about birth order when thinking about your own personality and that of your siblings?

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