CET-6 Listening Practice: How Sleep Protects Memory

Good morning, everyone, and welcome to today's talk on sleep and memory. Most of us assume that forgetting simply happens with the passage of time. The longer ago we learned something, the more of it fades away. But is time really the main cause of forgetting? More than a hundred years ago, two American psychologists decided to put this idea to the test. In nineteen twenty-four, John Jenkins and Karl Dallenbach conducted a simple but clever experiment. They wanted to know whether sleep affects how quickly we forget new information. Two university students took part, and they were asked to learn short lists of nonsense syllables. These were meaningless combinations of letters, so the students could not rely on what they already knew. They were then tested after one, two, four or eight hours. Sometimes they spent that interval asleep, and sometimes they went about their normal daily activities. The results turned out to be remarkably clear! After eight hours of sleep, the students could still recall about half of the syllables. After eight hours awake, however, they remembered only around one syllable in ten! In other words, staying awake led to far more forgetting than sleeping did. The researchers concluded that forgetting is not simply a matter of time passing. Instead, new experiences during the day seem to interfere with what we have just learned. However, we should be careful not to draw strong conclusions from a single study. Only two people took part, which is an extremely small sample. Moreover, memorizing nonsense syllables in a laboratory is very different from studying real subjects. Fortunately, many later studies with far larger groups have produced similar results. Many scientists now believe that the sleeping brain actively strengthens new memories. This suggests that sleep is not wasted time, but an essential part of learning. So if you want to retain what you study, review it and then sleep on it. Staying up all night before an exam may well do more harm than good. Next time you are tempted to give up sleep for extra study, remember these two students. Thank you for listening, and sleep well tonight.