My thought (ha!) is that as one ages, there's just more context to swap into to think about something. Kids can flit about because everything around them doesn'

My thought (ha!) is that as one ages, there's just more context to swap into to think about something. Kids can flit about because everything around them doesn't overwhelm with context, whereas the elderly have experienced enough that any context switch carries a burdensome overhead. (That's what I meant by weighty thoughts.) I don't think intelligence has too much to do with it, except perhaps in overall speed in coping / filtering. (But here I'm just arguing about the number of teeth in a horse; the empiricist in me would like to be able to spend a few weeks with an academic article subscription to just survey the experiments that have been done. I bet there are lots!)