Sleep Boosts Memory

"Let me sleep on it" may just be the right advice for remembering complex information. Getting a good night's rest not only helps retention, but may even help us recall thoughts forgotten during the day, according to researchers from the University of Chicago.

Howard Nusbaum, a professor of psychology at the university, studied the effects of sleep on memory by testing the retention of words. Using a synthesizer, he distorted tapes of recorded speech, making the words difficult to understand. He then played the tapes back to college students, asking them to decipher the speech.

On first exposure, students understood just 21 percent of the words. After an hour of training, they understood 54 percent. "It is something like learning how to understand someone with a foreign accent," explains Nusbaum.

He then ran the same experiment with a second group of students, who were tested first at 9 in the morning and then tested again at 9 that night. This group remembered only remembered 31 percent of the words in the test at the end of the day. Yet after a night of sleep, their scores climbed up again: the following morning, the same students remembered 40 percent of the words.

A third group was tested at 9:00 in the evening, then again the next morning. Their retention was also 40 percent.

Apparently, in the process of cleaning up our scattered thoughts, sleep also finds the ones that were about to slip through the cracks. "Sleep might strengthen relevant associations and weaken irrelevant associations, improving access to memories," Nusbaum notes.