Durability of Storage 3

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1 Chapter 7 These two kinds of memory memory for general information and memory for personal events were labelled semantic and episodic memory, respectively, by University of Toronto psychologist Endel Tulving Of course, we are not constrained to the past in our time travelling. Our cognitive systems also allow us to experience the present and to travel forward in time to plan and anticipate things in the future. As the preceding discussion suggests, memory involves more than taking information in and storing it in some mental compartment. In fact, psychologists probing the workings of memory have had to grapple with three enduring questions: (1) How does information get into memory? (2) How is information maintained in memory? (3) How is information pulled back out of memory? Encoding involves forming a memory code. Storage involves maintaining encoded information in memory over time. Retrieval involves recovering information from memory stores. Retrieval is analogous to calling up a file and then displaying it on your computer monitor. Research issues concerned with retrieval include the study of how people search memory and why some retrieval strategies are more effective than others. Our memories change over time and are rough reconstructions rather than exact copies of past events. Just as memory involves more than storage, forget ting involves more than "losing" something from the memory store. Psychologists have observed a similar phenomenon in the laboratory, which they have dubbed the next in line effect. If participants in a small group take turns speaking to the group, subsequent memory tests reveal that the subjects tend to not recall much of what was said just before they took their turn The Role of Attention Attention involves focusing awareness on a narrowed range of stimuli or events. The key issue in this debate is whether stimuli are screened out early, during sensory input, or late, after the brain has processed the meaning or significance of the input 1 o Evidence on the "cocktail party phenomenon" suggests the latter. For example, imagine a young woman named Claudia at a crowded party where many conversations are taking place. Claudia is paying attention to her conversation with a friend and filtering out the other conversations. However, if someone in another conversation mentions her name, Claudia may notice it, even though she has been ignoring that conversation. In experimental simulations of this situation, about 35% of participants report hearing their own name When we are attending to complicated, high load tasks that consume much of our attentional capacity, selection tends to occur early. Wherever filtering occurs, it is clear that people have difficulty if they attempt to focus their attention on two or more inputs simultaneously. Although people tend to think that they can multitask with no deterioration in performance, research suggests that the human brain can effectively handle only one

2 attention consuming task at a time That may be fine in many circumstances, but the cost of divided attention does have profound implications for the controversy about the advisability of driving while conversing on a cellphone. suggest that while much of the information we want to remember is encoded as a result of effortful processing, some types of information may be acquired more automatically. Levels of Processing According to some theorists, differences in how people attend to information are the main factors influencing how much they remember. Structural encoding is relatively shallow processing that emphasizes the physical structure of the stimulus. phonemic encoding, which emphasizes what a word sounds like. Phonemic encoding involves naming or saying (perhaps silently) the words. Finally, semantic encoding emphasizes the meaning of verbal input; it involves thinking about the objects and actions the words represent. Levels of processing theory proposes that deeper levels of processing result in longer lasting memory codes. As predicted, the subjects' recall was low after structural encoding, notably better after phonemic encoding, and highest after semantic encoding Enriching Encoding Elaboration Elaboration is linking a stimulus to other information at the time of encoding. Elaboration often consists of thinking of examples that illustrate an idea. Visual Imagery Imagery the creation of visual images to represent the words to be remembered can also be used to enrich encoding. The beneficial effect of imagery on memory was demonstrated in a study by Paivio, Smythe, and Yuille (1968). They asked subjects to learn a list of 16 pairs of words. They manipulated whether the words were concrete, high imagery words, or abstract, lowimagery words. In terms of imagery potential, the list contained four types of pairings: impact of imagery is quite evident. The best recall was of high high pairings, and the worst recall was of low low pairings, showing that high imagery words are easier to remember than low imagery words. Dual coding theory holds that memory is enhanced by forming semantic and visual codes, since either can lead to recall. Self Referent Encoding Self referent encoding involves deciding how or whether information is personally relevant. The value of self referent encoding demonstrates once again that encoding plays a critical role in memory. But encoding is only one of the three key processes in memory. 2

3 Key Points Three key processes contribute to memory: encoding, storage, and retrieval. The nextin line effect illustrates that active encoding is crucial to memory. Attention, which facilitates encoding, is inherently selec tive and has been compared to a filter. The cocktail party phenomenon suggests that input is screened late in mental processing. The empirical evidence indicates that people may have some flexibility in where they place their attention filter. According to levels of processing theory, the kinds of memory codes people create depend on which aspects of a stimulus are emphasized. Structural, phonemic, and semantic encoding emphasize the structure, sound, and meaning of words, respectively. Deeper processing results in better recall of information. Structural, phonemic, and semantic encoding represent progressively deeper levels of processing. Elaboration enriches encoding by linking a stimulus to other information, such as examples of an idea. The creation of visual images to represent words can enrich encoding. Visual imagery may help by creating two memory codes rather than just one. Encoding that emphasizes personal self reference may be especially useful in facilitating retention. information processing theories was to subdivide memory into three separate memory stores the model devised by Richard Atkinson and Richard Shiffrin, which proved to be the most influential of the information processing theories. According to their model, incoming information passes through two temporary storage buffers the sensory store and short term store before it is transferred into a long term store Sensory Memory The sensory memory preserves information in its original sensory form for a brief time, usually only a fraction of a second. Sensory memory allows the sensation of a visual pattern, sound, or touch to linger for a brief moment after the sensory stimulation is over. In the case of vision, people really perceive an afterimage rather than the actual stimulus. Because the memory trace in the visual sensory store decays in about 1/4 of a second. Memory traces in the auditory sensory store also appear to last less than a second Short Term Memory Short term memory (STM) is a limited capacity store that can maintain unrehearsed information for up to about 20 seconds. o However, there is a way that you can maintain information in your short term store indefinitely. rehearsal the process of repetitively verbalizing or thinking about the information. o rehearsal or processing (e.g., Craik & Lockhart, 1972). In using maintenance rehearsal you are simply maintaining the information in consciousness, while in more elaborative processing, you are increasing the probability that you will retain the information in the future Durability of Storage 3

4 Theorists originally believed that the loss of information from short term memory was due purely to time related decay of memory traces, but follow up research showed that interference from competing material also contributes Capacity of Storage George Miller (1956) in a famous paper called The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information. Miller noticed that people could recall only about seven items in tasks that required them to remember unfamiliar material. A chunk is a group of familiar stimuli stored as a single unit. People routinely draw information out of their long term memory banks to evaluate and understand information that they are working with in short term memory. Short Term Memory as Working Memory Among other things, studies showed that short term memory is not limited to phonemic encoding as originally thought and that decay is not the only process responsible for the loss of information from STM. Baddeley's model o The first component is the phonological loop that represented all of STM in earlier models. This component is at work when you use recitation to temporarily remember a phone number. o The second component in working memory is a visuospatial sketchpad that permits people to temporarily hold and manipulate visual images. o The third component is a central executive system. It controls the deployment of o attention, switching the focus of attention and dividing attention as needed The fourth component is the episodic buffer, a temporary, limited capacity store that allows the various components of working memory to integrate information and that serves as an interface between working memory and long term memory. For example, studies showed that visual processing tasks that engaged the visuospatial sketchpad did not interfere much with verbal processing tasks that engaged the phonological loop, and vice versa Researchers are also making progress in identifying the brain areas and neural mechanisms that underlie various aspects of working memory Long Term Memory Long term memory (LTM) is an unlimited capacity store that can hold information over lengthy periods of time. According to this view, forgetting occurs only because people sometimes cannot retrieve needed information from LTM. Wilder Penfield in the 1960s to map brain function in patients undergoing surgery for epilepsy, he found that stimulation of the temporal lobe sometimes elicited vivid descriptions of events long past. flashbulb memories, which are unusually vivid and detailed recollections of momentous events. In a similar vein, subsequent research has undermined the notion that flashbulb memories 4

5 represent an instance of permanent storage. Although flashbulb memories tend to be strong, vivid, and detailed, studies suggest that they are neither as accurate nor as special as once believed Although the possibility cannot be ruled out completely, there is no convincing evidence that memories are stored away permanently and that forgetting is all a matter of retrieval failure Are Short Term Memory and Long Term Memory Really Separate? some theorists have expressed doubts about whether there really are separate memory A handful of theorists have questioned the concept of sensory memory on the grounds that it may be nothing more than perceptual processes at work, rather than memory. larger number of theorists have questioned the concept of short term memory on the grounds that it really isn't all that different from long term memory STM was thought to depend on phonemic encoding (based on sound), whereas LTM encoding was thought to be largely semantic (based on meaning). One perspective is to view short term memory as a tiny and constantly changing portion of long term memory that happens to be in a heightened state of activation How Is Knowledge Represented and Organized in Memory? How is knowledge represented and organized in memory? In other words, what forms do our mental representations of information take? Clustering and Conceptual Hierarchies clustering the tendency to remember similar or related items in groups. Even A conceptual hierarchy is a multilevel classification system based on common properties among items. A schema is an organized cluster of knowledge about a particular object or event abstracted from previous experience with the object or event. For These results suggest that people are more likely to remember things that are consistent with their schemas than things that are not. People sometimes exhibit better recall of things that violate their schema based expectations Thus, the impact of schemas on memory can be difficult to predict, but either way, it is apparent that information stored in memory is often organized around schemas. o Mark Baldwin of McGill University terms these representations of typical events surrounding interpersonal interactions as relational schemas He suggests that these relational schemas represent regularities in your interpersonal experience, much in the same way that your office schema represents regularities in your exposure to offices. Semantic Networks Much knowledge seems to be organized into less systematic frameworks, called semantic networks A semantic network consists of nodes representing concepts, joined together by pathways that link related concepts. The ovals are the nodes, and the words inside the ovals are the interlinked concepts. 5

6 The length of each pathway represents the degree of association between two concepts. Shorter pathways imply stronger associations. Semantic networks have proven useful in explaining why thinking about one word (such as butter) can make a closely related word (such as bread) easier to remember Connectionist Networks and Parallel Distributed Processing (PDP) Models connectionist models of memory take their inspiration from how neural networks appear to handle information. connectionist, orparallel distributed processing (PDP), models assume that cognitive processes depend on patterns of activation in highly interconnected computational networks that resemble neural networks A PDP system consists of a large network of inter connected computing units, or nodes, that operate much like neurons. Like an individual neuron, a specific node's level of activation reflects the weighted balance of excitatory and inhibitory inputs from many other units. PDP models assert that specific memories correspond to particular patterns of activation in these networks Key Points Information processing theories of memory assert that people have three kinds of memory stores: a sensory memory, a short term memory, and a long term memory. The sensory store preserves information in its original form, probably for only a fraction of a second. Short term memory has a limited capacity of about seven chunks of information. STM can maintain unrehearsed information for up to about 20 seconds. Short term memory is working memory, and it appears to involve more than a simple rehearsal loop. According to Baddeley, working memory also includes a visuospatial sketchpad, an executive control system, and an episodic buffer. Long term memory is an unlimited capacity store that may hold information indefinitely. Penfield's ESB research and the existence of flashbulb memories suggest that LTM storage may be permanent, but the evidence is not convincing. Flashbulb memories are not as accurate as claimed. Some theorists have questioned the distinction between shortterm and long term memory. Information in long term memory can be organized in simple clusters or multilevel classification systems called conceptual hierarchies. A schema is an organized cluster of knowledge about a particular object or sequence of events. Semantic networks consist of concepts joined by path ways. Research suggests that activation spreads along the paths of semantic networks to activate closely associated words. Parallel distributed processing models of memory assert that specific memories correspond to particular patterns of activation in connectionist networks. Some theorists maintain that understanding retrieval is the key to understanding human memory Using Cues to Aid Retrieval The tip of the tongue phenomenon the temporary inability to remember something you know, accompanied by a feeling that it's just out of reach is Fortunately, memories can often be jogged with retrieval cues stimuli that help gain 6

7 access to memories. Reinstating the Context of an Event Another principle of memory articulated by Tulving was the encoding specificity principle. He suggested that your memory for information would be better when the conditions during encoding and retrieval were similar The technique of reinstating the context of an event has been used effectively in legal investigations to enhance eyewitness recall The eyewitness may be encouraged to retrieve information about a crime by replaying the sequence of events. According to Fergus Craik (Brown & Craik, 2000) and others, the effects of matching the person's internal state of encoding at the retrieval phase is just a special case of the encoding specificity principle. if you encoded information while intoxicated, your recall should be facilitated by attempting to retrieve the information while in a similar state similar effects are observed when considering the match or mismatch between the emotional state at encoding and retrieval of the individual attempting to retrieve the information some of these effects may account for red outs, or amnesia, by the perpetrators of violent crime for the crime itself. Reconstructing Memories and the Misinformation Effect To some extent, your memories are sketchy reconstructions of the past that may be distorted and may include details that did not actually occur As you might expect, subjects condensed the story, leaving out boring details. Subjects often introduced entirely new elements and twists. Modern schema theories also emphasize the reconstructive nature of memory misinformation effect has shown that reconstructive distortions show up frequently in eyewitness testimony. The misinformation effect occurs when participants' recall of an event they witnessed is altered by introducing misleading post event information. o In the first stage, subjects view an event. In the second stage, they are exposed to information about this event, some of which is misleading. In the third stage, their recall of the original event is tested to see if the post event misinformation altered their memory of the original event. Source Monitoring and Reality Monitoring Source monitoring is the process of making attributions about the origins of memories. Marcia Johnson and her colleagues maintain that source monitoring is a crucial facet of memory retrieval that contributes to many of the mistakes that people make in reconstructing their experiences these decisions are so easy and automatic, people make them without being consciously aware of the source monitoring process. In other instances, however, they may consciously struggle to pinpoint the source of a memory. 7

8 A source monitoring error occurs when a memory derived from one source is misattributed to another source. For instance, in studies of eye witness suggestibility, some subjects have gone so far as to insist that they "remember" seeing some thing that was only verbally suggested to them. cryptomnesia inadvertent plagiarism that occurs when people come up with an idea that they think is original, when they were actually exposed to it earlier Reality monitoring refers to the process of deciding whether memories are based on external sources (one's perceptions of actual events) or internal sources (one's thoughts and imaginations). Key Points The tip of the tongue phenomenon shows that recall is often guided by partial information about a word. Rein stating the context of an event can facilitate recall. This factor may account for cases in which hypnosis appears to aid recall of previously forgotten information. How ever, hypnosis seems to increase people's tendency to report incorrect information. Memories are not exact replicas of past experiences. As Bartlett showed many years ago, memory is partially reconstructive. Research on the misinformation effect shows that information learned after an event can alter one's memory of it. Source monitoring is the process of making attributions about the origins of memories. Source monitoring errors appear to be common and may explain why people some times "recall" something that was only suggested to them or something they only imagined. Reality monitoring involves deciding whether memories are based on perceptions of actual events or on just thinking about the events. Forgetting can reduce competition among memories that can cause confusion. In a recent exploration of this hypothesis, scientists used brain imaging technology to track neural markers of cognitive effort in a series of tasks in which participants memorized pairs How Quickly We Forget: Ebbinghaus's Forgetting Curve o The first person to conduct scientific studies of forget ting was Hermann Ebbinghaus. He published a series of insightful memory studies way back in forgetting curve, graphs retention and forgetting over time. Ebbinghaus's forgetting curve shows a precipitous drop in retention during the first few hours after the nonsense syllables were memorized. When subjects memorize more meaningful material, such as prose or poetry, forgetting curves aren't nearly as steep. Measures of Forgetting Retention refers to the proportion of material retained (remembered). o The three principal methods used to measure forgetting are recall, recognition, and relearning A recall measure of retention requires subjects to reproduce information on their own without any cues. A recognition measure of retention requires subjects to select previously learned information from an array of options. o One view is that recognition tests are especially sensitive measures of retention. The other 8

9 view is that recognition tests are excessively easy measures of retention. A relearning measure of retention requires a subject to memorize information a second time to determine how much time or how many practice trials are saved by having learned it before. Why We Forget Ineffective Encoding Since you can't really forget something you never learned, this phenomenon is sometimes called pseudoforgetting. People usually assume that they know what a penny looks like, but most have actually failed to encode this information. Even when memory codes are formed for new information, subsequent forgetting may be the result of ineffective or inappropriate encoding For example, if you're distracted while you read your text books, you may be doing little more than saying the words to yourself. This is phonemic encoding, which is inferior to semantic encoding for retention of verbal material. Decay Decay theory proposes that forgetting occurs because memory traces fade with time. o According to decay theory, the mere passage of time produces forgetting. Interference Interference theory proposes that people forget information because of competition from other material. o interference by varying the similarity between the original material given to subjects (the test material) and the material studied in the intervening period. Retroactive interference occurs when new information impairs the retention of previously learned information. o Retroactive interference occurs between the original learning and the retest on that learning, during the retention interval proactive interference occurs when previously learned information interferes with the retention of new information. Retrieval Failure As we suggested earlier in our discussion of context and state dependent encoding, one theory is that retrieval failures may be more likely when a mismatch occurs between retrieval cues and the encoding of the information you're searching The encoding specificity principle states that the value of a retrieval cue depends on how well it corresponds to the memory code This principle provides one explanation for the inconsistent success of retrieval efforts. Another line of research also indicates that memory is influenced by the "fit" not just between the cues present during encoding and retrieval, but also by the degree of match between the type of processing engaged in at encoding and retrieval. Transfer appropriate processing occurs when the initial processing of information is similar to the type of processing required by the subsequent measure of retention o Thus, retrieval failures are more likely when there is a poor fit between the processing done during encoding and the processing invoked by the measure of retention 9

10 Motivated Forgetting o Freud asserted that people often keep embarrassing, unpleasant, or painful memories buried in their unconscious. repression refers to keeping distressing thoughts and feelings buried in the unconscious The Repressed Memories Controversy Many of them have seemed genuinely baffled by the accusations, which have torn some previously happy families apart The crux of the problem is that child abuse usually takes place A handful of recovered memory incidents have been substantiated by independent witnesses or belated admissions of guilt by the accused Support for Recovered Memories Many psychologists and psychiatrists, especially clinicians involved in the treatment of psychological disorders, largely accept recovered memories of abuse at face value The clinicians who accept the authenticity of recovered memories of abuse attribute the recent upsurge in recovered memories to therapists' and clients' increased sensitivity to an issue that people used to be reluctant to discuss. Skepticism Regarding Recovered Memories They point out that the women in the Williams (1994) study may have failed to report their earlier sexual abuse for a variety of reasons besides amnesia, including embarrassment, poor rapport with the interviewer, normal forgetfulness, or a conscious preference not to revisit painful experiences from the past The skeptics do not say that people are lying about their previously repressed memories. Using hypnosis, dream interpretation, and leading questions, they supposedly prod and probe patients until they inadvertently create the memories of abuse that they are searching for (1) overly prone to see signs of abuse where none has occurred (2) unsophisticated about the extent to which memories can be distorted (3) naïve about how much their expectations and beliefs can influence their patients' efforts to achieve self understanding. Those who question the accuracy of repressed memories also point to findings on the misinformation effect, research on source monitoring errors, and other studies that demonstrate the relative ease of creating "memories" of events that never happened When subjects recall the words on each list, they remember the nonpresented target word over 50% of the time, and when they are given the final recognition test, they typically indicate that about 80% of the nonstudied target words were presented Skepticism about the validity of recovered memories of abuse has also been fuelled by the following observations and research findings: Many repressed memories of abuse have been recovered under the influence of hypnosis. Moreover, research shows that bogus dream interpretations can lead normal subjects to believe that they actually experienced the events suggested in the dream analyses Some recovered memories have described incidents of abuse that occurred before the victim reached age three and even when the victim was still in the womb 10

11 Rebuttals to the Skeptics Kluft (1999) argues that a recantation of a recovered memory of abuse does not prove that the memory was Harvey (1999) argues that laboratory demonstrations that it is easy to create false memories have involved insignificant memory distortions that do not resemble the emotionally wrenching recollections of sexual abuse that have been recovered in therapy. Olin (1994) concludes, "The possibility of implanting entire multiple scenarios of horror that differ markedly from the individual's experience, such as memories of childhood abuse in an individual who does not have a trauma history, remains an unsubstantiated hypothesis" Conclusions At this point, we don't have adequate data to estimate what proportion of recovered memories of abuse fall into each category On the other hand, recovered memories of abuse cannot be summarily dismissed, and it would be tragic if the repressed memories controversy made people overly skeptical about the all too real problem of childhood sexual abuse. The repressed memories controversy deserves one last comment regarding its impact on memory research and scientific conceptions of memory. The controversy has helped inspire a great deal of research that has increased our understanding of just how fragile, fallible, malleable, and subjective human memory is. Key Points Ebbinghaus's early studies of nonsense syllables sug gested that people forget very rapidly. Subsequent research showed that Ebbinghaus's forgetting curve was exceptionally steep. Forgetting can be measured by asking people to recall, recognize, or relearn information. Different methods of measuring retention often produce different estimates of forgetting. Recognition measures tend to yield higher estimates of retention than recall measures. Some forgetting, including pseudoforgetting, is due to ineffective encoding of information. Decay theory pro poses that forgetting occurs spontaneously with the passage of time. It has proven difficult to show that decay occurs in long term memory. Interference theory proposes that people forget information because of competition from other material. Proactive interference occurs when old learning interferes with new information. Retroactive interference occurs when new learning interferes with old information. Forgetting may also be a matter of retrieval failure. According to the encoding specificity principle, the effectiveness of a retrieval cue depends on how well it corresponds to the memory code that represents the stored item. Repression involves the motivated forgetting of painful or unpleasant memories. Recent years have seen a surge of reports of recovered memories of sexual abuse in child hood. The authenticity of these repressed memories is the subject of controversy because empirical studies have demonstrated that it is not all that difficult to create false memories. The evidence suggests that therapists can unknowingly create false memories in their 11

12 patients and that a significant portion of recovered memories of abuse are the product of suggestion. But it also seems likely that some cases of recovered memories are authentic. Wilder Penfield's work with electrical stimulation of the brain during surgery suggested that the cortex houses exact tape recordings of past experiences James McConnell rocked the world of science when he reported that he had chemically transferred a specific memory from one flatworm to another. McConnell (1962) created a conditioned reflex (contraction in response to light) in flat worms and then transferred RNA The Biochemistry of Memory alterations in synaptic transmission at specific sites. According to this view, specific memories depend on biochemical changes that occur at specific synapses. research that earned a Nobel prize for Kandel, they showed that reflex learning in the sea slug produces changes in the strength of specific synaptic connections by enhancing the availability and release of neurotransmitters at these synapses Manipulations that alter hormone levels shortly after an organism has learned a new response can affect memory storage in a variety of animals. James McGaugh (2002, 2004) theorizes that hormones influence memory storage by modulating activi W in the amygdala and a variety of neurotransmitter systems in the brain. Other animal studies suggest that adequate protein synthesis is necessary for the formation of memories The Neural Circuitry of Memory In other words, memories may create unique, reusable pathways in the brain along which signals flow. Thompson has traced the pathway that accounts for a rabbit's memory of a conditioned eye blink response. the cerebellum, a structure in the hindbrain (see Figure 7.21). When this spot is destroyed, the conditioned stimulus no longer elicits the eye blink response, even though the unconditioned stimulus still does The key implication of this work is that it may be possible to map out specific neural circuits that correspond to at least some types of specific memories. Long term potentiation (LTP) is a long lasting increase in neural excitability at synapses along a specific neural pathway. Researchers produce LTP artificially by sending a burst of high frequency electrical stimulation along a neural pathway, but theorists suspect that natural events produce the same sort of potentiated neural circuit when a memory is formed neurogenesis the formation of new neurons may contribute to the sculpting of neural circuits that underlie memory. As we noted in Chapter 3, scientists have discovered that new brain cells are formed constantly in the dentate gyrus of the hippocampus The Anatomy of Memory Retrograde amnesia involves the loss of memories for events that occurred prior to the onset of amnesia. Anterograde amnesia involves the loss of memories for events that occur after the onset of amnesia. 12

13 H. M. had a relatively normal childhood until, on his 16th birthday, he suffered his first of many grand mal seizures By 1953 he was having as many as 11 epileptic seizures a week and he needed some type of intervention. He had surgery to relieve debilitating epileptic seizures in M.'s memory losses were originally attributed to the removal of his hippocampus Based on decades of additional research, scientists now believe that the entire hippocampal region (including the hippocampus, dentate gyrus, subiculum, and entorhinal cortex) and the adjacent parahippocampal region are critical for many types of long term memory Many theorists believe that the hippocampal region plays a key role in the consolidation of memories Consolidation is a hypothetical process involving the gradual conversion of information into durable memory codes stored in long term memory. According to this view, memories are consolidated in the hippocampal region and then stored in diverse and widely distributed areas of the cortex One recent advance has been the demonstration that the amygdala seems to be critical to the formation of memories for learned fears Researchers exploring the anatomy of memory have traditionally focused on the anatomical bases of long term memory. However, recent years have brought progress in understanding the neural correlates of working memory. Alan Baddeley (2003) suggests that the central executive component of working memory may be localized in the prefrontal cortex, whereas other components of working memory may be housed elsewhere. Key Points Memory traces may reflect alterations in neurotransmitter release at specific locations. Manipulations of hormone levels and protein synthesis can affect memory. Thompson's research suggests that memory traces may consist of localized neural circuits. Memories may also depend on long term potentiation, which is a durable increase in neural excitability at synapses along a specific neural pathway. Memory formation may also stimulate neural growth. In retrograde amnesia, a person loses memory for events prior to the amnesia. In anterograde amnesia, a person shows memory deficits for events subsequent to the onset of the amnesia. Studies of amnesia and other research suggest that the hippocampal complex is involved in the consolidation of memories. Implicit versus Explicit Memory As noted earlier, patients with anterograde amnesia often appear to have no ability to form long term memories. o Thus, the amnesiacs do remember words from the list. Implicit memory is apparent when retention is exhibited on a task that does not require intentional remembering. explicit memory, which involves intentional recollection of previous experiences. To draw a parallel with everyday life, implicit memory is simply incidental, unintentional remembering Implicit memory is unconscious, must be accessed indirectly, and can best be assessed 13

14 with variations on relearning (savings) measures of retention. Implicit memory is largely unaffected by amnesia, age, the administration of certain drugs (such as alcohol), the length of the retention interval, and manipulations Some theorists think these differences are found because implicit and explicit memory rely on different cognitive processes in encoding and retrieval The declarative memory system handles factual information. nondeclarative or procedural memory system houses memory for actions, skills, operations, and conditioned responses. Some theorists believe that an association exists between implicit memory and the procedural memory system (Squire, Knowlton, & Musen, 1993). Why? Because memory for skills is largely unconscious. People execute perceptual motor tasks such as playing the piano or typing with little conscious awareness of what they're doing. Another parallel with implicit memory is that the memory for skills (such as typing and bike riding) doesn't decline much over long retention intervals. Declarative memory appears to be handled by the hippocampal complex and the far flung areas of the cortex with which it communicates Semantic versus Episodic Memory The episodic memory system is made up of chronological, or temporally dated, recollections of personal experiences. Her episodic memory is so powerful that it "dominates" her waking life AJ seems to be able to accurately remember almost everything that happened to her, especially since she was 14 years old. Episodic memory is important to us in terms of keeping a record of our personal experiences. It is important to us in other ways too. The semantic memory system contains general knowledge that is not tied to the time when the information was learned. Episodic memory is like an autobiography, while semantic memory is like an encyclopedia. Prospective versus Retrospective Memory Prospective memory involves remembering to perform actions in the future. retrospective memory involves remembering events from the past or previously learned information. Retrospective memory is at work when you try to recall who won the Stanley Cup last year, when you reminisce about your high school days, or when you try to recall what your professor said in a lecture last week. Key Points Implicit memory involves unintentional remembering, whereas explicit memory involves intentional recall. Implicit memory is unconscious, must be accessed indirectly, and is largely unaffected by amnesia, age, drugs, and the length of the retention interval. Declarative memory is memory for facts, while procedural memory is memory for actions and skills. Theorists suspect that the declarative memory system handles explicit memory, whereas the procedural memory system handles implicit memory. Declarative memory can be subdivided into episodic memory for personal facts and semantic memory for general facts. Theorists have also distinguished between 14

15 retrospective memory (remembering past events) and prospective memory (remembering to do things in the future). Our discussion of memory enhances our understanding of why people's experience of the world is highly subjective. Work in this area also shows that behaviour is governed by multiple causes and that psychology is characterized by theoretical diversity. 15