Is There a Difference Between Firstborn and Only Children?

Even firstborn children, it is now well established that there is a slight IQ difference. But I don't think there's a lot of evidence for firstborn or only children being higher or lower in any kind of dramatic way on any personality trait or unhappiness either. So I don't know if we gave Ian anything even remotely useful. Well, he can't make a podcast, dammit. Let me just annotate a bit your observation or your understanding. My screed, my rant.