Well, here’s the first one: younger siblings are cooler.
Just kidding. Despite having a horse in this race, I’ll try to maintain some objectivity and give older siblings a fair shake. In fact, older siblings can be pretty awesome.
Still, research on how birth order influences personality and cognition have found that while both older and younger siblings have some things going for them, they do have differences, at least from a statistical point of view. Here are three:
- Perfectionistic self-presentation: A study published in September found that first-born siblings are more likely to display what psychologists call perfectionistic self-presentation. As the name suggests, perfectionistic self-presentation is a tendency to portray oneself as perfect and to hide one’s imperfections. It has been linked to psychological distress.
- Risk taking: If younger siblings are less perfectionistic, you might hypothesize that they’d also be less risk-averse – and you’d be right. At least in the context of athletics. Research published in 2010 showed that younger siblings are 1.48 times more likely to participate in high-risk sports and that major league baseball players who are younger brothers are 10.6 times more likely to attempt stealing bases than those who are older brothers.
- Intelligence: Yes, this might be the trump card in birth order research. According to a massive study of 20,000 people from 3 countries, older siblings are a little smarter on average. The same study also found, somewhat disappointingly for those of us who like to contemplate the differences between older and younger siblings, that birth order does not seem to affect personality traits like agreeableness, conscientiousness, emotional stability, extraversion or imagination.
Despite the research that’s been done, scientists still have very little understanding of why there are these subtle differences between siblings or why birth order affects some traits but not others. So you might want to wait for a little more research to come out before you go and throw these results in the face of your poor brother or sister!