Interesting. I've read that all caffeine does is stimulate your adrenal gland, which I guess would make sense with the not being able to learn new tasks thing. Adrenaline is a major part of the fight or flight response. If he was drinking 6 pots a day I can see why he wasn't sleeping well.
I don't drink it that much; usually once a week. On Monday mornings I go to Sheetz and get a frozen late because I have to get up at about 6:30 to take my boyfriend into work, which is too early, but too late to go back to sleep. Most of my caffeine comes from tea, soda, and chocolate.