Jorge, one of my students, quickly dispelled any myths I had about siesta as we slammed back our second round of espresso. Children take naps every day, he told me, not adults. "Usually on the weekends you have a big lunch and siesta with the family," he said. "But not during the week. No one has the time."

For centuries in Spain and Latin America, heading home for lunch and a snooze with the family was something like a national right, but with the ubiquity of global capitalism standardizing work hours, this idyllic habit is fast becoming an endangered pleasure. Ironically, all this is happening just as researchers are beginning to note the health benefits of the afternoon nap.

According to a nationwide survey, less than 25 percent of Spaniards still enjoy siestas. And like Spain, much of Latin America has adopted Americanized work schedules, too, with shortened lunchtimes and more rigid work hours. Last year the Mexican government passed a law limiting lunch breaks to one hour and requiring its employees to work their eight-hour shift between 7 a.m. and 6 p.m. Before the mandate, workers would break up the shift -- going home midday for a long break with the family and returning to work until about 9 or 10 p.m. The idea of siesta is changing in Greece, Italy and Portugal, too, as they rush to join their more "industrious" counterparts in the global market.

Most Americans I know covet sleep, but the idea of taking a nap midafternoon equates with laziness, unemployment and general sneakiness. Yet according to a National Sleep Survey poll, 65 percent of adults do not get enough sleep. Numerous scientific studies document the benefits of nap taking, including one 1997 study on the deleterious effects of sleep deprivation in the journal Internal Medicine. The researchers found that fatigue harms not only marital and social relations but worker productivity.

According to Mark Rosekind, a former NASA scientist and founder of Alterness Solutions in Cupertino, Calif., which educates businesses about the advantages of sanctioning naps, we're biologically programmed to get sleepy between 3 and 5 p.m. and 3 and 5 a.m. Our internal timekeeper -- called the circadian clock -- operates on a 24-hour rotation and every 12 hours there's a dip.

Rosekind recommends that naps be either for 40 minutes or for two hours. Forty minutes keeps you in non-REM (rapid eye movement) sleep, the physical restoration part of the cycle, and two hours lets you go into a more complete rotation of non-REM and REM. (REM sleep, in simple terms, is when our mental repair takes place and when we usually dream.) During the night REM and non-REM alternate more or less in 90-minute cycles. Napping anywhere in between cuts into the two loops, so it's better to stop the cycle before it starts -- after 40 minutes -- or let it run its course -- two hours. Latin American countries, asserts Rosekind, have had it right all along. They've been in sync with their clocks; we haven't.

Since most of the world is sleep-deprived, getting well under the recommended eight hours a night (adults get an average of 6.5 hours nightly), we usually operate on a kind of idle midday. Naps are even more useful now that most of us forfeit sleep because of insane work schedules, longer commute times and stress. In a study published last April, Brazilian medical researchers noted that blood pressure and arterial blood pressure dropped during a siesta.