Now, a new UC Davis study shows that children who have older brothers tend to become more aggressive than those with older sisters. The study, published in the September/October 2007 issue of the journal Child Development, had the following findings:
- Having a brother or a highly aggressive sibling of either gender can lead to greater increases in aggression over time.
- Older siblings with younger sisters tend to end up less aggressive.
- Older siblings who were aggressive tended to have younger siblings who were also aggressive, and vice versa.'