Thomas Edison apparently only slept 3-4 hours a night, and sometimes stayed awake for 2 to 3 days on end. But I'm not Thomas Edison and feel like a freak on a leash if I don't get at least 7-8 hrs a night. Saying that, I probably get only around 5 hrs on average - and I don't feel smarter, that's for sure. P.s @antonette - please link the article which states insomnia causes intelligence. This seems highly dubious and most likely a generalization at best. ;)