Most of us rely on artificial stimulants to power through the day, with full-time employees consuming on average 3 cups of coffee/soda per day. Caffeine enhances alertness and concentration. But its effects, if any, on higher cognitive functions like learning and memory are debatable. In terms of really recharging one's mind in the middle of the day, what most of us need, experts say, is a good nap.
For night shift workers, however, researchers have found that a combination of naps and caffeine had the most beneficial effect. The nap-and-caffeine cocktail improves alertness and performance during hours when the body is naturally inclined to sleep.