Enter coffee, stage right. Caffeine is perhaps the most widely used stimulant in our general population. It helps us get through those non-optimal periods for productivity when we compelled to be productive anyway. Caffeine makes us feel alert and attentive. It is a highly lipid soluble, so it tends to cross from the bloodstream into the brain quickly and we feel its effects relatively quickly. In animals, caffeine has shown that it reaches peak accumulations in the brain within minutes of ingestion (Ryan et. al. 2002: 68). And it hangs around in the brain, stimulating the regions that control sleep, mood, and concentration, slowly dissipating over three to four hours (68)—which is plenty of time for you to get through your morning inbox, survive the staff meeting, return a few calls, and then get ready for lunch. (Though as Peter Lipson correctly reminded me, regular coffee drinkers do not get the same boost from the caffeine in coffee as do those who are not regular imbibers. Lipson recommends this paper, and points out that for regular coffee drinkers, the caffeine mitigates withdrawal symptoms, which we incorrectly associate with a stimulating boost.)