I agree with the other comments here that it is a rather common sense effect, but it has eluded psychological research until now (which is what makes me questio

I agree with the other comments here that it is a rather common sense effect, but it has eluded psychological research until now (which is what makes me question it). I know plenty of people who have a common sense view that birth order is important. So that part isn't missing. I can't even grasp how many times I've heard about the middle child being so different. Or being a typical little brother, etc. For me the question is, if it is so obvious and measurable, why is this the first study that finds this obvious effect.