21 March 2022

No Evidence that Siblings’ Gender Affects Personality


In a forthcoming paper in Psychological Science, Assistant Professor and associated CEBI-member Anne Ardila Brenøe (University of Zurich) answers the question whether siblings' gender affects personality. She has carried out the work together with her coauthors Jan Feld, Thomas Dudek, and Julia Rohrer.

Siblings are a central part of the childhood family environment, which is often believed to play a crucial and long-lasting role in personality development. For example, growing up with siblings of the opposite gender (as opposed to the same gender) may lead to different interactions between siblings and their parents.

These different interactions may in turn leave a mark on one’s personality. However, existing theories make opposing predictions—siblings of the opposite gender may plausibly either result in less gender-stereotypical personalities (e.g., a girl may take on more masculine traits because she imitates her brother) or more gender-stereotypical personalities (e.g., a girl may take on a more feminine role to differentiate herself from her brother).

“Previous empirical studies have resulted in inconsistent findings,” tells Anne Brenøe “and we therefore wanted to test this in a rigorous and comprehensive way.”

To test whether sibling gender affects personality development, Anne Brenøe and her coauthors compiled a unique data set by combining 12 large representative surveys covering 9 countries (the United States, the United Kingdom, the Netherlands, Germany, Switzerland, Australia, Mexico, China, and Indonesia). Their joint efforts resulted in a data set including nearly 90,000 individuals, which is many-fold the sample sizes used in previous studies. They investigated the personality traits risk tolerance, trust, patience, locus of control, and the Big Five.

The gender of the next younger sib is essentially random, giving them a nice natural experiment. That does not hold for the gender of the next older sibling, which may affect which parents move on to have another child (or not).

They found no meaningful causal effects of the gender of the next younger sibling, and no associations with the gender of the next older sibling. “Based on high statistical power and consistent results in the overall sample and relevant subsamples, our results suggest that siblings’ gender does not systematically affect personality,” explains Anne Brenøe.

You can read up on the results here

Does that mean that sibling gender does not matter? It does not! Anne Brenøe has shown in previous work that, in Denmark, brothers increase women's gender conformity, with consequences for labor market outcomes.

“It just seems that the personality measures we consider are not part of that story. Maybe they are simply a blunt tool when it comes to gendered dynamics,” says Anne Brenøe.