Perhaps it takes a bit more "intelligence" to keep one's attention focused for long periods on the kinds of subtle clues that one would first get of danger out

Perhaps it takes a bit more "intelligence" to keep one's attention focused for long periods on the kinds of subtle clues that one would first get of danger out in the dark beyond the cave. And it could be a mutually reinforcing thing, in one direction, the higher IQ provides the right skills to form thoughts that keep the listening-&-watching game interesting longer and that interest gives one personal motivation to stay up. In the other direction, groups who delegated this job to those with higher IQ did better; as those members are better able to tease the right danger signals out of the noises in the dark. I.e. do you want the smart guy or the idiot to watch for the wolves as you sleep? I want someone at least as smart than all the wolves put together. Personally speaking, I know my most creative schemes (leave aside the question of paranoid or not) for attacking/robbing a house all came as I sat listening to the sequences of noises from outside the house... trying to determine if I needed to use the flashlight or yard lights to confirm/dispel danger, weighing the benefits against giving my attention/position away to anyone who might be out there.