Middle children from large families more likely to be friendly and fair, study claims

The debate has raged for more than a century: does birth order help to shape personality, or are conscientious firstborns and creative youngest children flawed stereotypes based on flimsy evidence?

- Ian Sample

After decades of contested claims, a handful of recent studies found that there was little evidence for meaningful differences. But in a new study published yesterday, psychologists have pushed back and claim that there is an effect after all.

In one of the largest studies ever conducted on birth order, family size and personality, Canadian researchers gathered data from more than 700,000 volunteers and found that, on average, middle children scored higher than their siblings on traits seen as important for cooperation.

Scores were also higher in families with more children, suggesting that people may be more likely to develop a cooperative personality when they are raised as part of a bigger group.

The effects are not large, but psychology professors Michael Ashton at Brock University in Ontario and Kibeom Lee at the University of Calgary in Alberta believe they challenge the idea that birth order and the number of children raised together have no meaningful impact on personality.