Memory is the ability to remember something that has been learned or experienced. Memory also refers to the brain’s ability to store information. Memory is a vital part of the learning process. Without it, learning would be impossible. If your brain recorded nothing from the past, you would be unable to learn anything new. All your experiences would be lost as soon as they ended, and each new situation would be totally unfamiliar. Without memory, you would repeatedly have the same experiences for the “first time.” Memory gives a richness to life–the pleasure of happy remembrances as well as the sorrow of unhappy ones.
Scientists learn more every day about what happens in the brain when it stores memories. Almost certainly, storing new memories involves chemical changes in the nerve cells of the brain or in the substances that carry messages across the tiny gaps between the nerve cells. These gaps are called synapses. Storing new memories also involves structural changes, such as changes in the physical structure of the brain’s nerve cells.
Scientists also continue to learn more about which areas of the brain are involved in remembering. One important area is the hippocampus, part of a larger structure called the cerebral cortex. The cerebral cortex controls higher brain functions such as thinking, problem solving, decision making, and the use of language. Many people who suffer damage to the hippocampus have trouble remembering anything new.
The memory system
Psychologists divide a person’s memory system into three types, each of which has a different time span. These types are called sensory memory, short-term memory, and long-term memory.
Sensory memory
holds information for only a second or two. Suppose you look at a picture of a mountain. A nearly exact image of the mountain is stored briefly in your visual sensory memory, which involves your eyes and parts of your brain. However, the image quickly fades and disappears unless you make an active effort to think about it.
Short-term memory
contains what you actively think about at any particular time. It can hold a fact for as long as you think about it. You use short-term memory when you look up a telephone number and repeat it to yourself until you dial it. Unless you continually repeat this information to yourself, it will fade after about 20 to 30 seconds.
Long-term memory
can store facts, ideas, and experiences after you stop thinking about them. All conscious processing of information–such as when you think or when you solve problems–involves short-term memory working together with long-term memory. Psychologists refer to this combination as working memory. Long-term memory includes a huge amount of information, some of which lasts a lifetime. Experts believe that by the time a person dies, the long-term memory has stored hundreds of times the amount of information in a comprehensive encyclopedia, such as World Book.
Measuring memory
There are many methods to measure how much a person remembers. Three common methods are (1) recall, (2) recognition, and (3) relearning. Suppose you give a party and someone asks you a few weeks later who was there. The simplest way to find out how much you remember is to list as many names as you can. This is the method of recall.
In recognition, the person asking about your guests would give you a list of names. The list would include names of people who were at the party and of others who were not. You could then indicate which people were there. Most people can recognize more facts than they can recall. As a result, most students perform better on multiple-choice tests than on essay tests.
In relearning, you would memorize the party guest list after apparently forgetting it. Most people relearn information faster than they learned the information the first time. Scientists regard the difference in the time required for the original learning and for the relearning as evidence of how much was remembered.
Why people forget
In general, people forget more and more as time passes. An hour after a party ends, you probably could remember most of the people who were there. Two days later, you might recall only a few of the guests. A month later, you probably would remember even fewer. Scientists have devoted much study to why the passage of time makes people unable to remember things they once knew. The chief explanations for forgetting include interference, retrieval failure, motivated forgetting, and constructive processes.
Interference
occurs when the remembering of certain learned material blocks the memory of other learned material. If a friend moves, you may have difficulty recalling his or her new telephone number. The person’s old number may keep coming to mind and interfering with your remembering the new one. But after you have thoroughly learned the new number, you may not even be able to recall the old one.
The above example illustrates two types of interference. Previously learned information may hamper a person’s ability to remember new material. This hampering process is called proactive interference. Likewise, the learning of new facts may interfere with the memory of something previously learned. Such interference is known as retroactive interference.
Retrieval failure
is the inability to recall information that has been stored in the memory. You probably have had the experience of being unable to think of a name or some other piece of information that was on the tip of your tongue. Later, the information came to you naturally and effortlessly. Such temporary loss of memory, which occurs frequently, is called retrieval failure. Scientists compare it to trying to find a misplaced object in a cluttered room. The information is not gone, but neither can it be recalled immediately.
Motivated forgetting
occurs when people want to forget something. Some psychologists distinguish between two kinds of motivated forgetting, suppression and repression. In suppression, a person consciously tries to forget a memory. For example, singers might deliberately put out of their minds the memory of the last time they sang off key. In repression, a person unconsciously tries to forget a memory. Sigmund Freud, the Austrian physician who developed psychoanalysis as a method of treating mental illness, believed that people often get rid of memories of traumatic events through the process of repression. But scientists have not proved this theory.
Constructive processes
can involve the creation of false memories. When you try to remember an event that happened years ago, you may recall only a few facts. Using those facts, you fill in the gaps with details that seem to make sense but may be untrue. The process of constructing probable happenings to tell a complete story is called confabulation. Confabulated memories seem real and are almost impossible to distinguish from memories of events that actually occurred.
Improving memory
Memory experts believe that people can, with practice, increase their ability to remember. One of the most important means of improving memory is the use of mental aids called mnemonic devices << nih MON ihk >> . Other techniques can also be used to help people improve their memory.
Mnemonic devices
include rhymes, clues, mental pictures, and other methods. One of the simplest ways is to put the information into a rhyme. Many people remember the number of days in each month by using a verse that begins, “Thirty days hath September… .”
Another method provides clues by means of an acronym, a word formed from the first letters or syllables of other words. For example, the acronym homes could help a person remember the names of the Great Lakes–Huron, Ontario, Michigan, Erie, Superior.
A mental picture can be provided by the key-word method, which is particularly useful in learning foreign words. Suppose you want to remember that the German word Gabel << GAH behl >> means fork. First, you think of a key word in English that sounds like the foreign word–for example, gobble. Next, you connect the two words through a mental image, such as that of a person gobbling food with a fork. From then on, to recall the meaning of Gabel, you would remember gobble and the stored image linking it to fork.
Mental pictures can also be used to remember names. When you meet a person for the first time, pick out a physical feature of the individual and relate it to his or her name. For example, if you meet a very tall man named Mr. Shackley, imagine his bumping his head on the roof of a shack. In the future, this image will help you remember his name when you see or think of him.
Mnemonic techniques work best for remembering lists of specific items, such as words or objects. They do not work well for learning complex materials, such as stories and poems. For this reason, many psychologists favor more general strategies for improving memory.
Other ways to improve memory.
A good way to help remember a piece of information is to rehearse (repeat) it a number of times. You can rehearse aloud or quietly to yourself. The more you rehearse, the more lasting the memory will be. In addition to repeating the information over and over, rehearsal also can involve elaborating upon the information. For example, suppose you want to remember the year that the telephone was invented–1876. You might elaborate upon this information by reminding yourself that the Declaration of Independence was signed 100 years earlier.
Another memory aid involves making the surroundings in which you remember material similar to those in which you learned the material. For this reason, football coaches often require players to practice under conditions similar to those of an actual game.
Uncommon memory conditions
Exceptionally good memory.
You sometimes hear of someone who has a “photographic memory,” which supposedly works like a camera taking a picture. A person with such a memory would be able to take a quick mental picture of a textbook page or a scene. Later, the person could describe the page or scene perfectly by causing the image to reappear in his or her mind.
No one actually has a photographic memory. However, some people have a similar ability called eidetic imagery. An eidetic image is a picture that remains in a person’s mind for a few seconds after a scene has disappeared. People who have eidetic imagery can look at a scene briefly and then give a thorough description of the scene based on a mental image. But the image fades quickly and may be inaccurate. Eidetic imagery is rare. Only 5 to 10 percent of all children have this ability, and most of them lose it as they grow up.
Certain people possess an exceptionally good memory. They may be able to memorize the names of all the state capitals or hundreds of names and numbers from a telephone book. When such exceptional memory occurs in people with mental handicaps, psychologists refer to this condition as savant << suh VAHNT >> syndrome.
Déjà vu
(pronounced DAY zhah VOO) is the feeling of having already experienced a situation that is actually happening for the first time. For example, a person who goes to a restaurant in a foreign city for the first time may have the overwhelming sensation of having been there before. Episodes of deja vu occur most often in people who have epilepsy. Déjà vu is a French term meaning already seen.
Memory disorders.
Some memory disorders result from physical damage to the brain. Such physical damage may occur due to head injuries, drug abuse, infection, and other causes. For example, a blow to the head can cause a person to forget events that occurred before the injury. A person’s inability to remember these events is called retrograde amnesia. How much memory loss occurs depends on the severity of the injury. Football players who receive a blow to the head might forget the few seconds just before the injury. Someone who suffers major brain damage in a car accident might lose months or even years of memories. Brain-injured people also can experience anterograde amnesia. This condition involves difficulty remembering events that occur after the injury.
Memory difficulties also may result from emotional shock. For example, a person who witnessed a horrible accident may forget details of the accident. Memory loss in the absence of physical injury is known as psychogenic amnesia.
