I'm pretty sure that in the general population, there are at least as many people with older siblings as there are people with only younger siblings. But in this poll, it's 6 vs 19. That looks like a humongous effect (which we also found in SIAI-associated people, and which this poll was intended to further check). I could see some sort of self-selection bias and the like, and supposedly oldest children have slightly higher IQs on average, but on the whole I'm stumped for an explanation. Anyone?

ETA: Here's a claim that "it is consistently found that being first-born is particularly favourable to high levels of scientific creativity". See also this.

Vote this up if you are the oldest child with siblings.

Vote this up if you have older siblings.

Vote this up if you are an only child.

Vote this down for karma balance.