Everyone knows that caffeine is useful on occasion if we need to stay alert, especially when we’re sleepy.  Is there any college graduate who hasn’t had a caffeine-fueled all-night study session before an exam?  I certainly remember several nights in which I drank coffee to the point of inability to blink, much less sleep. But for those who drink a lot of coffee daily, how much of a boost in alertness are they getting?  A study in this issue of Neuropsychopharmacology offers an interesting insi...