Theory of birth order effect on personality debunked

The idea that sibling birth order affects personality has been around since the early 1900s, and became entrenched after Dr. Frank Sulloway published his book Born to Rebel in 1996.

A new study has debunked this theory. The study, published in the Proceedings of the National Academy of Sciences, has found “no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination”. The study has, however, confirmed that first-born siblings have a higher IQ across a wide study sample, but the effect is slight and not universal.

This leads the study authors to conclude that:

On the basis of the high statistical power and the consistent results across samples and analytical designs, we must conclude that birth order does not have a lasting effect on broad personality traits outside of the intellectual domain.

Source: ABC Science.

Also published on Medium.