Pulling an all-nighter for that big test tomorrow? Put the books down and get some sleep.

A new study released yesterday by Robert A. Stickgold, assistant professor of psychiatry at Harvard Medical School, suggests that without sleep, a person's memory of dates and places is only fleeting.

Students would be better off getting a solid night's sleep than cramming for a few extra hours, he said.

Stickgold also said his study belies a frequent assumption of college students everywhere--that sleepless nights can be made up a few days later when things slow down.

"The students engage in what I call 'sleep bulimia,' in which they binge sleep on weekends and purge, abstaining from sleep all week long," he said. "It's going to be just as destructive as real bulimia."

For his study, Stickgold trained 24 students to recognize a pattern of diagonal lines flashed briefly on a computer screen. Half the students then enjoyed a good night's sleep. The other half were kept up through the entire night.

Three days later, Stickgold found that the students who pulled an all-nighter weren't any better at recognizing the line patterns than they had been originally. The students who slept, however, remembered the patterns and recognized them more easily.

"Regardless of when we trained the subject, they cannot show improvement in performance until they've slept on it," Stickgold said.