The idea that birth order determines siblings' personality and intelligence has been debunked by a team of researchers.
Psychologists from Leipzig and Mainz analyzed central personality traits of over 20,000 grown-ups from Germany, the USA and Great Britain and found that who we become, only marginally correlates with our birth position amongst siblings.
The question of whether a person's position among siblings has a lasting impact on personality has occupied scientist for more than 100 years. Laypeople as well a scientist share a number of beliefs: Firstborns are supposedly perfectionists, for example, while middle children develop a talent for diplomacy and last-borns are expected to be rebellious.
Researchers found that central personality traits such as extraversion, emotional stability, agreeableness, and conscientiousness are not affected by birth-order position. Only regarding self-reported intellect small effects were found: Firstborns were more likely to report a rich vocabulary and less difficulty understanding abstract ideas.
Researcher Stefan Schmukle said that they found no substantial effects of birth order on any of the personality dimensions we examined. "This does not only contradict prominent psychological theories, but also goes against the intuition of many people."
The study appears in Proceedings of the National Academy of Sciences.