Human Memory
The Basics Since learning and remembering are closely linked, teachers can benefit from understanding the fundamentals of human memory.
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The human mind is a marvel and a mystery. How does it work? What are its limitations? How can it be improved? For a long time, these questions have been difficult to answer, but recent research has, at last, brought insight into how the mind functions. One key breakthrough has been the invention of the digital computer. The computer provides an analogy for understanding the human mind. No analogy is perfect, so it’s important to realize that the mind is like a computer in some ways but quite different in others. One similarity is that both have memory — in fact, both the human mind and digital computers have different kinds of memory. But there are also differences. Unlike a computer, the human mind has emotions. We feel happy, sad, worried, or excited, but such emotions seem unnatural for computers. Humans also have agency, or what we call will; in our minds, we have purposes and intentions, and we form plans. Again, it’s hard to think SOPHISTICATED PRIMER of computers as having these characteristics. These differences aside, computers and minds share enough similarities to make a comparison worthwhile. A computer has different kinds of memory. One form is active memory, called RAM. RAM is temporary: If the power is shut off accidentally, the computer loses its recent in-
MICHAEL E. MARTINEZ is a professor of education at the University of California, Irvine.
May 2010
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Michael E. Martinez
formation. A computer also has long-lasting, durable memory, which is stored in its hard drive. Human memory also has different forms. Some human memory, called long-term memory, is relatively durable. The mind also has memory that’s temporary, called short-term memory. These two forms of memory work together to form the mind’s basic structure — its cognitive architecture. You can gain insight into short-term memory by thinking about your own active thoughts. What are you thinking about right now? Whatever you’re thinking about in the moment — whether about a special person, politics, or pizza — that’s the content of your short-term memory. You can think about only a few ideas in your short-term memory at any one time. Maybe you can think of five common objects or five of your best friends all at once. Perhaps you can think about 10 things. But the number is limited. So, one characteristic of short-term memory is that its capacity is rather small. Long-term memory has a very large capacity. Your mind has stored hundreds of thousands of pieces of knowledge: names, facts, and life experiences. It’s all in your long-term memory. But, like short-term memory, long-term memory also has serious limitations. In particular, the contents of your long-term memory may not be particularly complete or accurate. Information flows between short-term and longterm memory. Depending on the direction of flow, different kinds of thinking result. For example, when information flows from short-term memory into long-term memory — when it leaves a longlasting trace — it produces learning. Information can also flow the other way, from long-term memory back into short-term. This happens whenever we think about a previously known fact, person, or event. That process is called recognition or recall, or just plain remembering. These two processes, learning and remembering, are important in daily life, and perhaps especially for students. But they are not necessarily easy. For better or worse, we don’t remember all the information we ever experience. After all, daily life brings millions of pieces of information to our awareness, and we pay brief attention to much of it, then discard it. We store in long-term memory only a fraction of what we experience in life. Learning is not automatic. Every good student knows that to form a long-term memory trace, or what we call learning, often requires quite a bit of effort. Even if some information is learned, it may be difficult to remember it again at some later time. Sometimes, you know that you know, but you can’t seem to bring the needed information back into your awareness, that is, from long-term memory
back into short-term memory. Thus, both processes — learning and remembering — can be difficult. LANGUAGE AND IMAGES
The mind deals with various kinds of information. Certainly, language is important. We communicate with words, as well as in other ways. Linguistic skill is important for the development of every child and for the child’s integration into the larger society. But language also has a second function that’s extremely important. Not only do we use language to communicate, we also use language to think. For example, whenever you reason through a difficult problem, chances are you use language inside your own mind to figure out things and to keep yourself on track. Language might well be the most obvious way When learning takes place, whether in schools or in other contexts, learners must see the meaning — they must find the pattern — in what is learned. that information is stored in the mind, but human memory holds other kinds of information too. For example, it can store information as mental pictures. Imagine, for example, what an apple looks like. In your mind’s eye, perhaps you can see an image of a shiny apple — red or green or yellow. The image of an apple might be very vivid, showing the shiny skin and tiny flecks of white or gold. Your mental image is not necessarily static. Maybe you can rotate the apple image in your mind. Maybe you can peel it or slice it. Your mental picture of an apple shows that the mind can hold images as well as words. Such images may not be pictures. The images can also be experienced in other sensory forms, such as taste or smell. A special kind of dynamic imagery is experienced like movies inside the head. You may be able to replay experiences from your past like a mental video. Perhaps your personal memories can be re-experienced at will. The memories may be so vivid that you don’t doubt their accuracy. But are your memories of the past truly accurate? Do you store your personal experiences in long-term memory exactly as they occurred? In other words, does your memory work like a videocamera? The answer is no — human memory does not function like a videocamera. But this answer is not obvious: One common myth is that our minds store every experience that we have ever had during an entire lifetime. According to the myth, the brain stores all incoming information completely and accurately, pdkintl.org
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even if it has trouble recalling the information later. However, the mind is quite different from a video camera. For one thing, it stores only a fraction of the information it experiences; it doesn’t record everything. Instead, human memory is very selective in what is stored. Memory is unlike a video camera in yet another How can the mind have such significant limitations and yet be responsible for the accumulated marvels of civilization in science, medicine, engineering, literature, music, and the arts?
way. Not only is the mind selective in what it stores, it is also distortive. When we think about our previous experiences, we sometimes “remember” them in ways that are quite different from what actually happened. This is obvious when eyewitnesses to a crime remember the event quite differently. But even among friends and family members, there can be considerable disagreement about past events. As a general rule, human memory isn’t particularly accurate. It selects and distorts information. One exception to this rule is photographic memory, which psychologists call eidetic memory. Eidetic memory does exist, but it’s quite rare — and those who do remember fully, accurately, and in detail don’t necessarily benefit from their ability. The most famous case is the Russian man code-named “S,”
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whose memory was so jumbled with unimportant facts that he had difficulty keeping a job. Ultimately, he was unable to manage his life. It’s not inevitable that photographic memory will lead to problems, but the case of “S” shows that eidetic ability is not necessarily a gift. It can be a handicap. THE MIND’S LIMITATIONS
The mind’s structure — the cognitive architecture — has rather significant limitations. Short-term memory has a fairly small capacity, so that it’s hard to think about many things at once. A second limitation is that long-term memory doesn’t record experience completely and accurately. Instead, memories are highly selective and tend to distort what really happened. This presents a mystery: How can the mind have such significant limitations and yet be responsible for the accumulated marvels of civilization in science, medicine, engineering, literature, music, and the arts? Clearly, the human mind has produced amazing achievements. How could these achievements arise from minds that have such fundamental limitations? One solution to the paradox is that the human mind is exceptionally good at finding patterns. The mind does so by binding together information according to its meaningfulness. Meaningful connections can become so strong that the linked ideas form a new unit. For example, you can recognize the face, voice, and characteristic ways of behaving of a person you know well. Those diverse pieces of information are forged together to form a single unit: that person’s identity. Here’s where language comes in — when ideas are linked to form a pattern, we often give that pattern a name or other symbol. The name or symbol can be used to recognize recurrent patterns, to communicate with other people, and to think about both concrete concepts — such as “chair” — and abstract ones — such as “freedom” or the number seven. This bonding of related ideas is so common to human thinking, it usually goes unnoticed. Yet it applies to many different activities. In the game of chess, for example, a grandmaster sees the board not as isolated pieces, but rather as clusters. With experience, the chessboard becomes perceptually simpler over time. This makes it possible for some experts to see the chessboard entirely in the mind, even to play blindfolded. Similarly, ideas cluster as we gain experience in anything — in reading, for example, our memory clusters letters to form words. This clustering has a name — chunking. As our mind chunks its perceptions, short-term memory can hold more and more information. The capacity of shortterm memory doesn’t change — it’s still rather small
— but as each chunk grows in complexity, shortterm memory can handle more data. Chunking makes a complex world seem simpler. A second resolution to the paradox is that the connectivity of long-term memory applies not only to common patterns, or chunks, but also to ideas that are distantly related. For example, knowing how to play chess might help a person imagine strategic ways to advance a career or win a sports competition. The ability to detect distant similarities makes solving problems possible. It’s also the basis for creative thinking. The mind can combine an idea with other ideas in unusual ways. Sometimes, the product is a creative breakthrough that has lasting value, such as a novel, a musical composition, or a scientific discovery. These creative products can form enduring contributions to a culture. Like any tool, the mind always functions best when it’s used in ways that are consistent with its design. As we consider the mind’s architecture — its organization by short-term memory and long-term memory — we need to cooperate with that design, rather than to fight against it. We ought to appreciate what the mind does best. The mind is not a video camera; rather, it’s a pattern-finder and a patternChina This ad 4/5/10 1:20when PM learning Page 1 takes place, maker. means that
whether in schools or in other contexts, learners must see the meaning — they must find the pattern — in what is learned. Seeing the meaning requires making new information connect with what the mind already knows. Of course, prior knowledge differs from person to person, and so the meaning of each new experience will vary form one learner to
Human memory is very selective in what is stored.
the next. In some ways, what is learned and how it is learned will always be tailored to the individual. No two people, given the same experience, will learn precisely the same thing in the same way. In the end, this person-to-person variability is probably a good thing because, when a mind is teamed with other minds, the result can be greater creative insight and analytical power. When human minds work together productively, the result can be mutually catalyzing, and the combined reach can extend far beyond what the individual mind, acting alone, K can achieve.
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