I am also not sure if this a limiting or enhancing factor. But in general, I think, sleep, and 'how much of it' -- was reason (not consequence) of human's cogni

I am also not sure if this a limiting or enhancing factor. But in general, I think, sleep, and 'how much of it' -- was reason (not consequence) of human's cognitive development. I will admit, I have not found a set of repeatable studies to verify the above assertion. So just a thought.