Memory is the persistence of learning over time. One helpful model of human memory is the Atkinson-Shiffrin three-stage processing model, which describes how information is encoded, stored, and retrieved. More recent research has modified this model to incorporate the concept of working memory.
Although some types of information are encoded automatically, other types, including information involving meaning, imagery, and organization, require effort. Mnemonic devices that use imagery and that organize information into chunks aid memory. Organizing into hierarchies also helps.
Information first enters the memory through the senses. We register visual images via iconic memory and sound via echoic memory.
Although our memory for information just presented is limited to about seven items, our capacity for storing information permanently is essentially unlimited. The search for the physical basis of memory has focused on the synapses and their neurotransmitters and on brain circuits. The hippocampus processes explicit (declarative) memories; even more ancient brain regions—for example, the cerebellum—process implicit (nondeclarative) memories.
To be remembered, information that is “in there” must be retrieved with the aid of associations that serve as primers. Returning to the original context sometimes aids retrieval. While in a good or bad mood we often retrieve memories congruent with that mood. Forgetting sometimes reflects encoding failure. Without effortful processing, much of what we sense we never notice or process. Memories may also fade after storage—often rapidly at first and then leveling off. Retrieval failures may be caused by proactive or retroactive interference or even by motivated forgetting.
Memories are not stored as exact copies. Rather, they are constructed, using both stored and new information. Thus, when eyewitnesses are subtly exposed to misinformation after an event, they often believe they saw the misleading details as part of the event. Memory researchers are especially suspicious of long-repressed memories of sexual abuse that are “recovered” with the aid of a therapist or suggestive book.
Among strategies for improving memory are studying repeatedly, making material personally relevant, activating retrieval cues, using mnemonic devices, minimizing interference, getting adequate sleep, and self-testing.
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The Phenomenon of Memory and Information Processing
Memory is the persistence of learning over time through the storage and retrieval of information. In some ways, our memory is like a computer’s information-processing system. Information must be encoded, stored, and retrieved. Psychologists have offered several information-processing models of memory. One is connectionism, which views memories as emerging from interconnected neural networks. The Atkinson-Shiffrin three-stage processing model states that we first record tobe-remembered information as a fleeting sensory memory, from which it is processed into short-term memory, where we encode it through rehearsal for long-term memory and later retrieval. This model is limited and fallible because we sometimes bypass the first two stages and process some information automatically and directly into long-term memory without conscious awareness. Also, working memory is a newer and better understanding of short-term memory because it emphasizes a more active role in the second processing stage in which information is rehearsed, new stimuli are associated with existing memories, and problems are solved. The working-memory model includes the processing of incoming visual-spatial and auditory information.
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Unlike most computers, which do step-by-step serial processing, our brain engages in parallel processing. As a result, some encoding occurs automatically. With little or no effort, we process an enormous amount of information about space, time, frequency, and well-learned information. For example, we can re-create a sequence of the day’s events in order to guess where we might have left a coat. Automatic processing occurs without our awareness and without interfering with our thinking about other things. Some forms of processing, such as learning to read or drive, require attention and effort when we first perform them but with practice become automatic.
Automatic processing occurs unconsciously; effortful processing requires attention and effort. For example, our memory of names will disappear unless we rehearse them. The spacing effect is our tendency to retain information more easily if we distribute our rehearsal than if we practice in one long session. The serial position effect is our tendency to remember the last and first items in a long list (for example, a grocery list) better than the middle items. Immediately after learning, we remember the last items best (the recency effect); after a delay, we remember the first items best (the primacy effect).
When processing verbal information for storage, we usually encode its meaning. For example, we associate it with what we already know or imagine. Research indicates that semantic encoding (of meaning) yields better memory of verbal information than acoustic encoding (of sound) or visual encoding (of an image). We are particularly likely to remember words we can meaningfully relate to ourselves, called the self-reference effect. This research also highlights the futility of trying to remember words we do not understand and the benefits of rephrasing what we read and hear into meaningful terms.
In a variety of experiments, researchers have documented the benefits of mental imagery. For example, we remember concrete words that lend themselves to picture images better than we remember abstract, low-imagery words. We remember concrete nouns better than abstract nouns because, for example, we can associate both an image and a meaning with fire but only a meaning with process. Imagery is at the heart of many memory aids, or mnemonics. For example, in the peg-word system, people remember new items by using a visual as well as an acoustic code.
When we organize information into meaningful units, we recall it more easily. In chunking, we cluster information into familiar, manageable units, such as words into sentences. Chunking occurs so naturally that we often take it for granted. When people develop expertise in an area, they often process information in hierarchies composed of a few broad concepts divided and subdivided into lesser concepts and facts. In this way, experts can retrieve information efficiently.
Information first enters the memory system through the senses. Iconic memory is a momentary sensory memory of visual stimuli, a photographic or picture-image memory lasting for a few tenths of a second. Echoic memory is a momentary sensory memory of auditory stimuli. Even if attention is elsewhere, sounds and words can still be recalled within 3 or 4 seconds.
Our working/short-term memory span for information just presented is very limited—a secondslong retention of up to about seven items, depending on the information and how it is presented. Short-term recall is slightly better for random digits than for random letters, and slightly better for what we hear than what we see. Without rehearsal, most of us retain in short-term memory only about four information chunks.
Although we know that our capacity for storing information permanently is essentially unlimited, we are not sure how and where we store it. Research has shown that memories do not reside in a single place, and the so-called memory trace is difficult to find.
The search for the physical basis of memory is now focused on the synapses and their neurotransmitters and on the long-term potentiation (LTP) of brain circuits. In response to increased activity in neural pathways, neural interconnections form or strengthen. Studies of the sea slug indicate that when learning occurs, the slug releases more of the neurotransmitter serotonin at certain synapses, and these synapses become more efficient at transmitting signals. In experiments, rapidly stimulating certain memory-circuit connections has increased their sensitivity for weeks to come. This LTP appears to be a neural basis for learning and remembering associations. Drugs that block LTP interfere with learning. Scientists are developing and testing drugs that enhance long-term memory. One approach is to develop drugs that enhance the production of the protein CREB. Another is to develop drugs that boost glutamate.
The naturally stimulating hormones that we produce when excited or stressed make more glucose energy available to fuel brain activity, signaling the brain that something important has happened. The amygdala, two emotion-processing clusters in the brain’s limbic system, arouses brain areas that process emotion. These emotion-triggered hormonal changes help explain our flashbulb memories of surprising, significant events. Emotionless events mean weaker memories.
Studies of brain-damaged patients who suffer from amnesia reveal two types of memory. Implicit memory (nondeclarative memory) is retention without conscious recollection. Explicit memory (declarative memory) is the memory of facts and experiences that one can consciously know and “declare.”
Brain scans of people recalling words and autopsies of people who had amnesia reveal that the hippocampus, a limbic system structure, plays a vital role in the gradual processing of our explicit memories into long-term memory. The hippocampus is lateralized. Damage to one or the other seems to produce different results. With left-hippocampus damage, people have trouble remembering verbal information. With right-hippocampus damage, they have trouble recalling visual designs and locations. The hippocampus is not the permanent storehouse, but a loading dock that feeds new information to the cortex for permanent storage. Implicit memories are processed by the cerebellum. Research with rabbits in which different parts of the neural pathway were temporarily deadened during eye-blink training pinpointed implicit memory in the cerebellum at the back of the head. Our dual-memory system helps explain infantile amnesia.
Recall is a measure of memory in which the person must retrieve information learned earlier, as on a fill-in-the-blank test. Recognition is a measure in which a person need only identify items previously learned, as on a multiple-choice test. Relearning is a memory measure that assesses the amount of time saved when relearning previously learned information. Tests of recognition and relearning reveal that we remember more than we recall. We can think of a memory as held in storage by a web of associations. Retrieval cues are bits of related information we encode while encoding a target piece of information. They become part of the web. To retrieve a specific memory, we need to identify one of the strands that leads to it, a process called priming. Activating retrieval cues within our web of associations aids memory. Such activation may occur without our awareness.
Retrieval is sometimes aided by returning to the original context in which we experienced an event or encoded a thought. It can flood our memories with retrieval cues that lead to the target memory. Sometimes, being in a context similar to one we’ve been in before may trick us into subconsciously retrieving an earlier experience. The result is a feeling that we are reliving something that we have experienced before—a phenomenon known as déjà vu.
State-dependent memory is the tendency to recall information best in the same emotional state as when the information was learned. Memories are somewhat mood-congruent. While in a good or bad mood, we often retrieve memories consistent with that mood. For example, research suggests that currently depressed people recall their parents as rejecting, punitive, and guilt-promoting, whereas formerly depressed people describe their parents much as do those who have never suffered depression. Moods also prime us to interpret others’ behavior in ways consistent with our emotions.
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The capacity to forget useless or out-of-date information is helpful. Because of his inability to forget, the Russian memory whiz known as S found it more difficult than others to think abstractly—to generalize, to organize, to evaluate. Without an ability to forget we would be overwhelmed by out-of-date and irrelevant information. As noted by Daniel Schacter, our memories fail us through forgetting (absent-mindedness, transience, and blocking), through distortion (misattribution, suggestibility, and bias), and through intrusion (persistence of unwanted memories).
One explanation for forgetting is that we fail to encode information for entry into our memory system. Without effortful processing, much of what we sense we never notice or process. For example, most people in the United States have looked at thousands of pennies. However, when tested on specific features, they have difficulty recognizing the real thing.
Memories may fade after storage. From his research on learning and retention, Ebbinghaus found that forgetting occurs rapidly at first, then levels off. This principle became known as the forgetting curve. Storage decay may reflect a gradual fading of the physical memory trace. Another possible explanation is that we simply can’t retrieve the information.
Retrieval failure can occur if we have too few cues to summon information from long-term memory. It may also happen when old and new information compete for retrieval. In proactive interference, something we learned in the past interferes with our ability to recall something we have recently learned. In retroactive interference, something we have recently learned interferes with something we learned in the past.
With his concept of repression, Sigmund Freud proposed that our memories are self-censoring. To protect our self-concepts and to minimize anxiety, we may block from consciousness painful memories. In Freud’s view, this motivated forgetting submerges memories but leaves them available for later retrieval under the right conditions. Increasing numbers of memory researchers think repression rarely, if ever, occurs. More typically, we have trouble forgetting traumatic experiences.
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Memories are not stored as exact copies, and they certainly are not retrieved as such. Rather, we construct our memories, using both stored and new information. In many experiments around the world, people have witnessed an event, received or not received misleading information about it, and then taken a memory test. The repeated result is a misinformation effect: After exposure to subtle misinformation, many people misremember. Asking leading questions can plant false memories. As people recount an experience, they fill in their memory gaps with plausible guesses. Other vivid retellings may also implant false memories. Even repeatedly imagining and rehearsing nonexistent events can create false memories, called imagination inflation.
Our memory for the source of an event is particularly frail. In source amnesia, we attribute to the wrong source an event that we have experienced, heard about, read about, or imagined. Thus, we may recognize someone but have no idea where we have seen the person. Or we imagine or dream an event and later are uncertain whether it actually happened.
Because memory involves reconstruction as well as reproduction, we are unable to tell whether a memory is real by how real it feels. False memories created by suggested misinformation and misattributed sources may feel as real as true memories and may be very persistent. Just as perceptual illusions may seem like real perceptions, false memories may feel like real memories. However, memories we derive from experience have more detail than memories we derive from imagination.
Preschool children are particularly sensitive to suggestion, and their recollections of sexual abuse may be prone to error. When researchers have used suggestive interviewing techniques, they have found that most preschoolers and many older children can be induced to report false events. However, even young children can accurately recall events if a neutral person asks about their experiences in neutral words they can understand and uses less suggestive, more effective techniques.
Innocent people have been falsely convicted of abuse that never happened, and true abusers have used the controversy over recovered memories to avoid punishment. Forgetting of isolated past events, both negative and positive, is an ordinary part of life. Cued by a remark or an experience, we may later recover a memory. Controversy, however, focuses on whether the unconscious mind forcibly represses painful experiences and whether they can be retrieved by therapist-aided techniques. Memories “recovered” under hypnosis or drugs are especially unreliable, as are memories of things happening before age 3. Traumatic experiences are usually vividly remembered, not banished into an active but inaccessible unconscious.
The psychology of memory suggests several effective study strategies. These include studying repeatedly by using spaced practice; making new material personally meaningful by relating it to what is already known; mentally re-creating the contexts and moods in which the original learning occurred in order to activate retrieval cues; using mnemonic devices; minimizing interference, for example, by studying just before sleeping; sleeping more; and testing your own knowledge both to rehearse it and to determine what must still be learned.
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*Work Cited: All summary notes come from *Myers Pyschology for AP, Lecture Guides (2011 Worth Publishers)