According to a somewhat flawed study at the Medical University of Innisbruk, the area of the brain that is tied to working memory (the ability to maintain and manipulate new bits of info) "lit up" shortly after the test subject had the equivalent of two cups-o-joe. At the same time, those caffeinated subjects outperfromed the caffeine deprived in doing tasks designed to test short-term and working memory.
The flaw is they didn't seem to note how much caffeine test subjects normally consumed--maybe two cups was all they'd usualy have in a week (I've heard of such people), maybe two cups was what they needed to figure out how to get out of bed in the morning...it kinda makes a difference in this sort of thing.
Oh well...I suppose this could be file under "stuff we kinda already knew, but someone actually needed to study it to justify our addictions."
Here's the link to the Globe and Mail article--usual caveat about subscriptions...