Memory in Psychology
Memory in Psychology
The creation of new memories is an ability that occurs minute to minute in human beings (and some researchers would argue millisecond to millisecond) as people go about their daily lives encountering new information. In fact, although people sometimes need to intentionally remember an appointment date or a phone number, many of life’s everyday experiences are not intentionally rehearsed at the time for later remembering, but are created without intentional awareness. Human recall of certain events is not perfect, nor always detailed. This transformation of past events is influenced by many factors relating to events occurring in one’s environment and in the brain itself.
In 1968 Richard Atkinson and Richard Shiffrin were among the first researchers to propose that the formation of memories proceeds by passing through a series of stages. Information from the environment first flows through one’s sensory organs (responsible for vision, hearing, smell, touch, and taste) into what Atkinson and Shiffrin termed the sensory store. Memories are considered to be stored very briefly in this processing step because the flow of information through the sensory organs leaves only a temporary trace of the information—this is why waving a sparkler at night gives the illusion of a light trail. If an individual pays further attention to the incoming information, it enters a short-term or working memory system that allows additional processing (e.g., analyzing the meaning of a letter one is reading). When one “thinks” or works through a problem mentally, one is using working memory. This working memory system is limited in capacity so that there is only so much information that can be processed at one time. Another important function of working memory is to transfer information to longterm memory, where an infinite number of memories are capable of being stored indefinitely.
The process of storing memories is ultimately dependent on biological brain structures. Although it is still unknown “where” personal memories are stored in the brain, it is clear that certain brain structures are critical for storing and retrieving memories. A structure in the medial temporal region of the brain called the hippocampus has long been known to be important for the development of new memories. Numerous case studies have demonstrated that damage to the hippocampus leads to profound memory impairment. The most famous case study is that of an epileptic patient, H.M., whose hippocampus was surgically removed, leaving him with the inability to form any new memories despite the fact that he could remember events that occurred before the surgery and otherwise had a normal intelligence quotient (IQ).
The ability to remember information is based on two fundamental processes, encoding and retrieval. During encoding, incoming information is transmitted to the brain and is consolidated and prepared in the hippocampus and surrounding medial temporal regions for longterm memory storage. Although these regions play a primary role in preparing memories for long-term storage, the memories themselves are not stored there, but are distributed throughout the brain in a network. Once information has been properly encoded and stored in longterm memory, recalling these past events relies, in part, on the frontal lobes of the brain, responsible for organizational and strategic processing of information. Neuroimaging research suggests that the fontal lobes play a key role in memory processes because both encoding and retrieval processes are inherently strategic. That is, when one remembers an event, one often must remember when the event occurred relative to other events, how individual details contributed to the overall meaning of the events, and where the event occurred. In 1994 Endel Tulving and colleagues reported that the left frontal lobe may play a more active role during information encoding, whereas the right frontal lobe may be more responsible for retrieval.
The distinction between encoding and retrieval processes is key because if either process fails, a memory cannot be experienced. In the case of H.M. encoding processes were impaired so that new experiences were not stored in long-term memory. Other forms of disease-related damage to medial temporal brain regions (e.g., Korsakoff’s syndrome) also lead to an impaired ability to recall previously stored memories, often attributable to a retrieval, rather than an encoding, problem. Evidence from healthy individuals indicates that problems during encoding may be more responsible for memory failures relative to problems during retrieval. For example, it is common for a person to fail to remember the name of a recently met person, even though the introduction may have occurred only minutes before. When meeting someone new, one’s attention is drawn to many aspects of the person other than the name—what the person looks like, whom he or she knows, whom he or she is with, and other details of the encounter. Because one’s working memory is also engaged in these other processes, the specific name information may not be encoded sufficiently, so that no matter how hard one tries to later remember the name, that information is not accessible. In 1996 Fergus Craik and his colleagues substantiated these findings, showing that memory performance is much poorer when people are distracted when encoding information compared to distraction during retrieval.
In addition to conscious recollection of past experiences, memory can also be demonstrated subconsciously or automatically. The ability to ride a bike, type, read, and accomplish other familiar tasks relies on a memory of how to do these things. Psychologists in the past have used a number of terms to define the distinction between these learned skills and memories that are consciously recalled. In 1985 Tulving used the term procedural memory to describe these memories that were skill-based and learned through repetition over time. In contrast, Tulving used the term episodic memory to describe the conscious recollection of past events, and the term semantic memory to refer to memory of word meanings, facts, and concepts. Semantic and procedural memories have been shown to be more resistant to brain injury, disease, and aging than episodic memories. For example, although H.M. was unable to recall any new events that he experienced after his surgery, his vocabulary system was unaffected, and he was able to learn new complex skills as efficiently as others his age.
As people age, they typically notice that their memory is not quite as strong as it used to be. One theory proposed by Lynn Hasher and Rose Zacks in 1979 states that remembering often requires the use of substantial working memory resources and effort, which may decline as people age. Thus, recalling one’s new doctor’s name may be relatively more difficult as one ages because doing so requires one to engage these limited mental resources. When memory tasks, however, place less of a burden on these mental resources, an older adult’s memory performance is similar to that of a younger adult. For example, although one may have difficulty recalling a doctor’s name without prompts, one may easily identify the name on a directory list at the doctor’s health center. Research conducted in 1987 by Fergus Craik and Joan McDowd has confirmed that when presented with a list of words, young adults perform significantly better than older adults if required to later recall the words without assistance. The two age groups, however, often show similar memory performance when participants are later presented with the words and have to simply recognize those that were previously seen.
Hasher and Zacks proposed that this decline in working memory could be due to either a shrinkage in capacity with normal aging or to a difficulty inhibiting irrelevant information while remembering. Everyone has thoughts that drift in and out of consciousness during the day, but Hasher and Zacks believe that younger adults may be more efficient in inhibiting such thoughts when needed, leading to a less cluttered working memory space. In fact, in studies conducted by Zacks and colleagues in 1996, when told to purposefully forget information they had previously been instructed to remember, younger adults were more successful at this forgetting than older adults. Another theory of declining memory with age, put forth by Timothy Salthouse in 1996, suggests that brain cells (neurons) undergo the same degradation with age as the nerves in one’s arms and legs that move the muscles associated with these areas. Consequently, Salthouse argued, declining memory processes are the result of a “general slowing,” so that information in the brain is transmitted more slowly. In a sense, information can get backed-up and fade from memory before it can be used. Although there may be a gradual progression of general slowing as a person ages, other factors appear to either slow down or speed up memory declines. Educational status, social activity, exercise, cardiovascular disease, diabetes, and medications may all influence memory ability in old age.
Although older adults may have difficulty recalling more recently experienced events and information, they are nonetheless able to recall distant memories with clarity and detail. Psychological researchers typically refer to memories related to one’s self as autobiographical memories. Autobiographical memories may be distinct from other types of explicit memories because autobiographical memories are rich with contextual or situational detail. For example, recalling one’s wedding requires not just remembering information about the event (e.g., what food was served), but also recall of the time in one’s life that it occurred. This time-tag on the memory may also serve to help one recall other events surrounding the event (e.g., remembering the date of the event can help one remember where the event happened). These memories are not just organized by time period, but may also be organized around themes (e.g., “that happened during my long-haired hippie days”). Perhaps the most critical component of autobiographical memories is that they contain information related to the individual person and his or her own sense of self. Research conducted in 1997 by Cynthia Symons and Blair Johnson showed that people exhibit better memory performance when they are required to learn a list of adjectives (e.g., assertive) by how well each adjective applies to their own personality compared to conditions where they remember other similar words without self-reference.
This latter finding may explain why a reminiscence “bump” is observed when older adults are asked to recall as many events as they can from their life. Although people tend to recall many events from the most recent year, the number of memories recalled declines the older the memories are except for a bump (or period) that occurs during the teenage years through the mid-twenties of which people recall a good deal of memories. Martin Conway and David Rubin believe that this pattern may exist because the adolescent and early adult years are a time when the self is formed and thus this time becomes a dominant theme in one’s life resulting in more vivid memories of this period.
When studying autobiographical memories it is very difficult to establish whether a reported memory actually occurred—usually there is no one available to confirm or deny the accuracy of the memory. Further compounding this problem is the fact that human memory is not exact, but reconstructive in nature. That is, one’s recall of details surrounding an event is a combination of what actually happened and what one believes happened. These beliefs may or may not be true. Memory researcher Elizabeth Loftus has studied how people can come to “remember” events that never happened to them.
In 1978 Loftus and her colleagues first observed that participants’ memory of an actual event can be contaminated and changed when they hear a different account of the same memory from someone else. Loftus termed this phenomenon the misinformation effect. Perhaps more troubling is the finding that not only can memory be distorted by post-event information, but through the power of suggestion people can come to remember things that never even happened to them. A 2004 review by Loftus notes that even in laboratory settings people can come to believe that as children they were attacked by an animal or almost drowned in a pool, and come to remember things that never could have happened, such as seeing Warner Bros.’ Bugs Bunny at Disney World. Telling the participants that the following story they are about to hear came from a family member implants such memories. Participants then come to believe, with great confidence, that the story is true. Some therapists have been critical of Loftus’s theory, concerned that it may minimize or discount truly recovered memories of abuse that may occur in therapy sessions. Loftus, however, did not suggest that all recovered memories are necessarily false, but rather that some people may remember some things that did not happen if questioned in a particular way.
Not all participants in such studies adopt false memories—the range being around 20 to 50 percent for false memory adoption, depending on other variables, according to Loftus. Further, some individuals appear to be more susceptible than others. Those who have more creative imaginations and those who are more prone to memory or attentional lapses appear most susceptible. Studies involving false memories have received considerable attention from the media due to their relevance to judicial cases involving childhood sexual abuse and rape. Based solely on the testimony of children, day care workers at the Little Rascals day care center in Edenton, North Carolina, in 1988 were accused, charged, and convicted of orchestrating a child sexual abuse ring. Higher courts eventually overturned the cases involving the staff because the children’s accusations were the result of leading questions by investigators and therapists and were fueled by the children’s imaginations.
The Little Rascals day care case reveals the fluid and malleable nature of memory, especially during childhood, and how it is often difficult to distinguish between what actually happened and what sounds familiar due to repeated and leading questioning. In 1993 Marcia Johnson and her colleagues suggested that such problems can be attributed to internal source monitoring, or difficulties identifying the source of internalized experiences (e.g., whether the experience was real or imagined). The ability to make these internal source distinctions appears to be more difficult for children and older adults, compared to younger adults. Human memories are thus a product of what an individual actually experiences (or sometimes does not actually experience), and intervening information received after the event. How a person reflects on these memories later in life can also come to influence and change the perception of memory.
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Wythe L. Whiting
David J. Madden