This one is taken from Chapter 92 of Mind Hacks, a book published by O’Reilly. PDF = oreilly.com/catalog/mindhks/chapter/hack92.pdf

After you’ve drunk a cup of tea or coffee, the caffeine diffuses around your body, taking less than 20 minutes to reach every cell, every fluid (yes, every fluid) of which you’re made. Pretty soon the neurotransmitter messenger systems of the brain are affected too. We know for certain that caffeine’s primary route of action is to increase the influence of the neurotransmitter dopamine, although exactly how it does this is less clear. Upshifting the dopaminergic system is something caffeine has in common with the less socially acceptable stimulants cocaine and amphetamine, although it does so in a different way.

Neurons use neurotransmitters to chemically send their signals from one neuron to the next, across the synapse (the gap between two neurons). There are many different neurotransmitters, and they tend to be used by neurons together in systems that cross the brain. The neurons that contain dopamine, the dopaminergic system, are found in systems dealing with memory, movement, attention, and motivation. The latter two are what concern us here.Via the dopaminergic system, caffeine stimulates a region of the subcortex (the brain beneath the cerebral cortex) called the nucleus accumbens, a part of the brain known to be heavily involved in feelings of pleasure and reward. Sex, food, all addictive drugs, and even jokes cause an increased neural response in this area of the brain. What happens with addictive drugs is that they chemically hack the brain’s evolved circuitry for finding things rewarding—the ability to recognize the good things in life and learn to do more of them.

The jury is still out on whether most caffeine addicts are really benefiting from their compulsion to regularly consume a brown, socially acceptable, liquid stimulant. While some killjoys claim that most addicts are just avoiding the adverse effects of withdrawal, it is more likely that most people use caffeine more or less optimally to help them manage their lives. One study even went so far as to say “regular caffeine usage appears to be beneficial, with higher users having better mental functioning.” So it’s not just pleasure-seeking, it’s performance-enhancing.

Coffee is strongly associated with two things: keeping you awake and helping you do useful mental work. In fact, it can even be shown to help physical performance. The association with creative mental work is legendary, although the cognitive mechanisms by which this works are not clear. As early as 1933, experiments had shown that a cup of coffee can help you solve chess problems, but the need for experiments has been considered minimal given the massive anecdotal evidence. As the mathematician Paul Erdös said, “A mathematician is a device for turning coffee into theorems.” Academics, designers, programmers, and creative professionals everywhere will surely empathize.