Birth Order Has Only Very Modest Effect on Personality

Many laypeople as well as scientists have shared the belief that birth order has a lasting impact on personality.

A new German study appears to dispel this notion, suggesting that who we become only marginally correlates with our birth position among siblings.

Research psychologists from the universities of Mainz and Leipzig, Germany share their findings in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

The question of whether a person’s position among siblings has a lasting impact on personality has challenged psychologists for more than 100 years.

Common beliefs included: Firstborns are supposedly perfectionists, while middle children develop a talent for diplomacy, and last-born or the babies, are expected to be rebellious.

In the new study, researchers attempted to determine whether these differences actually exist.

Professor Stefan Schmukle and Julia Rohrer of Leipzig University and Professor Boris Egloff of Johannes Gutenberg University Mainz (JGU) analyzed the data of more than 20,000 grown-ups from Germany, the U.S., and Great Britain.

They found that central personality traits such as extraversion, emotional stability, agreeableness, and conscientiousness are not affected by birth-order position. Only self-reported intellectual variances were found: Firstborns were more likely to report a rich vocabulary and less difficulty understanding abstract ideas.

These self-reports are not completely unfounded as the study confirmed the already known small decline in objectively measured intelligence from first- to last-born.

“This effect on intelligence replicates very well in large samples, but it is barely meaningful on the individual level, because it is extremely small. And even though mean scores on intelligence decline, in four out of ten cases the later-born is still smarter than his or her older sibling,” explained Schnukle.

“The real news of our study is that we 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.”

Source: Johannes Gutenberg Universitaet Mainz/EurekAlert
Brothers photo by shutterstock.