Growing up with brothers vs. sisters: How does it affect your personality?
Now, an expansive study of more than 80,000 people in nine countries has what appears to be the definitive answer.
Having a sibling of a different gender does not affect one’s adult personality.
Study principal investigator Dr. Julia M. Rohrer, personality psychologist and lecturer for the Department of Psychology at the University of Leipzig, told Medical News Today:
“To clarify — we are looking at personality in adulthood rather than childhood personality. This is important to clarify because it could be that sibling gender does have effects on personality while people still live with their siblings, but which fade out later in life.”
“What surprised me was how consistently we couldn’t detect any effects on personality. We disaggregated the data in all sorts of ways to check whether there were effects in individual data sets, or maybe for certain birth cohorts, or maybe only for firstborns, et cetera. But we really came up mostly empty-handed!”
The researchers work with survey responses from people in the United States, the United Kingdom, the Netherlands, Germany, Switzerland, Australia, Mexico, China, and Indonesia.
Co-author Dr. Anne Ardila Brenøe, a research associate in the Department of Economics at the University of Zurich, said to Medical News Today:
“Given my own prior work, I had expected that having an opposite-sex sibling would increase gender-typed personality. We don’t find any evidence of this, which was surprising to me.”
The study appears in Psychological Science.