THE LOGIC OF SLEEP-LEARNING: Page 20

Despite the knowledge that one impression is sufficient to register permanently on our brain, repetition appears to be necessary to memorize material. The reason for this is not yet known. It is thought that there may be some relationship between the time the impression is made and the ability to recall it when awake. Sleep-learning psychologists hope to discover a means of triggering off recall of material, possibly an associa-tional symbol which will stimulate the recall much as the electric current did in Dr. Penfield's experiments. Meanwhile, sleep-memorization is based on repetition and free-association. Certain things have been found to be helpful in aiding retention of material. Motivation is important, as, for instance, thinking of the reward that will be enjoyed as a result of learning. Material that is understood is retained better than material learned by rote alone; repetition alone will affect memorization, but retention for any length of time requires the use of intelligence. Writing the material after learning it tends to shorten the time necessary for permanent learning, and repetition a few times after the material is learned aids in retention. New forms of presentation are no more effective than repetition of identical material; the latter is recommended to refresh the memory. The order of presentation seems to be important: the beginning and end of a lengthy sleep-study period are often better remembered than the middle parts, which seems an emphasis that the student should not attempt absorbing too much material in one night's sleep-study. In learning a language it appears more effective to