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Short-term Memory
短时记忆

There are two kinds of memory: short-term and long-term. Information in long-term memory can be recalled at a later time when it is needed. The information may be kept for days or weeks. Sometimes information in the long-term memory is hard to remember. Students taking exams often have this experience. In contrast, information in short-term memory is kept for only a few seconds, usually by repeating the information over and over. For example, you look up a number in the telephone book, and before you dial, you repeat the number over and over. If someone interrupts you, you will probably forget the number. In laboratory studies, subjects are unable to remember three letters after eighteen seconds if they are not allowed to repeat the letters to themselves.

Psychologists study memory and learning with both animal and human subjects. The two experiments here show how short-term memory has been studied.

Dr. Hunter studied short-term memory in rats. He used a special apparatus which had a cage for the rat and three doors. There was a light in each door. First the rat was placed in the closed cage. Next, one of the lights was turned on and then off. There was food for the rat only at this door. After the light was turned off, the rat had to wait a short time before it was released form its cage. Then, if it went to the correct door, it was rewarded with the food that was there. Hunter did this experiment many times. He always turned on the lights in a random order. The rat had to wait different intervals before it was released from the cage. Hunter found that if the rat had to wait more than ten seconds, it could not remember the correct door. Hunter's results show that rats have a short-term memory of about ten seconds.

Later, Dr. Henning studied how students who are learning English as a second language remember vocabulary. The subject in his experiment were 75 students at the University of California in Los Angeles. They represented all levels of ability in English: beginning, intermediate, advanced, and native-speaking students.

To begin, the subjects listened to a recording of a native speaker reading a paragraph in English. Following the recording, the subjects took a 15-question test to see which words they remembered. Each question has four choices. The subjects had to circle the word they had heard in the recording. Some of the questions had four choices that sound alike. For example, weather, whether, wither, and wetter are four words that sound alike. Some of the questions had four choices that have the same meaning. Method, way, manner, and system would be four words with the same mean

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