Study suggests siblings don't shape character

The finding of an international study by researchers from Leipzig University, the University of Zurich and Victoria University of Wellington, New Zealand that our personality as adults is not determined by whether we grow up with sisters or brother.

The results have now been published in the renowned journal "Psychological Science".

Siblings play a central role in childhood, and so it seems reasonable to assume that they influence each other's personalities in the long term. In fact, psychological research has been dealing with the question of what difference it makes whether people grow up with sisters or brothers for more than half a century.

Scientists have repeatedly investigated whether brothers and sisters influence the extent to which their siblings adopt traditional "gender-conforming" characteristics, i.e. characteristics that are considered "typically male" or "typically female" in society. There are many assumptions and also contradictory findings on this, which is due in part to the fact that earlier studies were often based on limited and not very robust data.

In order to shed light on the previously inconsistent data situation, a team of researchers has now analysed data from more than 80,000 adults from nine countries, including Germany and the US, but also Mexico and China, for example. This was made possible by various national longitudinal studies that systematically collect information about people over decades, including their living conditions and personality traits determined in various ways. Statistical analysis of this data showed across national borders that personality traits such as risk-taking, emotional stability, conscientiousness and patience are not systematically related to sibling gender.

"Our findings refute the idea that growing up with brothers or sisters causes us to develop certain personality traits in the long term that are considered 'typically female' or 'typically male' in a society," explains Dr Julia Rohrer, one of the authors of the paper. "Overall, current research suggests that siblings have a surprisingly small impact on personality in adulthood. For example, previous studies by our research group here in Leipzig show that sibling position - that is, whether a person is a firstborn or a sandwich child, for example - also does not play a major role in personality."

However, the results of the new study do not mean that sibling gender does not play a role at all in long-term life paths. Economic studies have shown that in the US and Denmark, women with brothers earn less when employed. "So there do seem to be some interesting dynamics here that are related to gender," says Rohrer. "But personality is probably not part of the explanation for such effects."