A Jolta Java

A Jolta Java

Looking for a quick cognitive boost? Go ahead, fill up your coffee mug. Psychologist Harris Lieberman, Ph.D., of the U.S. Army Research Institute of Environmental Medicine, in Natick, Massachusetts, has been studying how to maintain alertness in soldiers. Caffeine works, says Lieberman, by blocking the neurotransmitter adenosine, which normally calms the brain. "The clearest effect of caffeine on cognition is its ability to enhance vigilance." Caffeine helps sustain attention during performance of various cognitive tasks for long periods of time.

Used in moderation, caffeine appears to be safe, Lieberman says. Unless pregnant, the average person can safely use coffee and tea as a habitual wake-up call, up to his or her personal "jitter threshold."