Memory
Psychologists, in recent years, have attempted to developed theories of memory using the computer as a model. These information-processing theories of memory are based on the apparent similarities between the operation of the human brain and that of the computer. In this model information can be followed as it moves through the following operations: input, storage, and retrieval. At each point in the process, a variety of control mechanisms ( such as attention, storage, and retrieval ) operate. Information enter the memory system through the sensory receptors. Attention operates at this level to select information for further processing. The raw sensory information that is selected is then represented--- or encoded in a form (sound, visual image, meaning) that can be used in the next stage of memory.Other control mechanisms might then transfer selected information into more permanent memory storage. When the stored information is needed, it is retrieved from memory. The information-processing model is represented by the stage theory of memory:
Stages of Memory
Include three stages representing a continuous process, and considered as a closely linked three stages of memory rather than three separate memories.
A-Sensory Register Stage: ( Immediate Memory )
It is very brief, designed to hold an exact image of each sensory experience in the sensory register long enough to locate and focus on relevant bits of information and transfer them into the next stage of memory. For visual information, this ''snapshot'' fades very quickly, probably lasting about one-quarter of a second in most cases. For, a vivid image of what we hear is retained for about the same length of time, one-quarter of a second, but weaker '' echo'' is retained for up to 4 seconds. The information stored in the sensory register does not last long, but it's apparently a complete replica of the sensory experience. Visual information in the sensory register is lost and replaced so rapidly with new information that we seldom aware we even have such a memory store.
B-Short-Term Memory:
When a bit of information is selected for further processing, it transferred from the sensory register into short term memory-or STM . It is not necessary to intentionally transfer information to STM; generally just p aying attention to the information is enough to transfer it. Once information has been transferred to short term memory, a variety of control processes may be applied. Rehearsal and chunking are two important examples of these control processes
a-Rehearsal: For Overcoming STM's Limited Life Span, as short term memory is good for only temporary storage of information .In general, information is lost from STM in less than half a minute ( 30 sec.) unless it is 'renewed, 'and it is often lost in only a few seconds. Fortunately, information can be renewed in STM by mental repetition, or rehearsal, of information. When a grocery list is rehearsed regularly in this way, it can be held in STM for relatively long periods of time. If the list is not rehearsed, however, it is soon lost. .
The information stored in STM can be of many different types of memories: the smell of perfume, the notes of melody, the test of a fruit, the shape of a nose, the finger positions in a guitar chord, or a list of names. But humans have a preference for transforming information into sounds, or acoustic codes, whenever possible for storage in STM, we probably use acoustic codes in STM as much as possible because it is easier to rehearse by mentally talking to ourselves than by mentally repeating the images of sights, smells, and movements. Nonetheless, STM can store any form of information that can enter the brain through the senses.
b-Chunking: For Overcoming STM's Limited Capacity---as the storage capacity is quite limited. The exact capacity differs slightly for different kinds of information, but as the psychologist George Miller(1956) put it, it is constant enough to call it the magic number- seven plus or minus two. i.e. rarely are we able to hold more than five to nine bits of information in STM, regardless of the nature of that information. This is very limited capacity. STM is serves another important function, which further limits its already small capacity- it serves as our working memory. This means that space in STM is used when old memories are temporarily brought out of long-term memory to be used or updated. Space in STM is also used when we think about this information.
To improve the capacity of STM there are some effective ways.
1-To learn the information well enough to transfer it into long-term memory,
2-To put more information into the 7 plus-minus 2 units of STM. These units of memory are called chunks, as in grouping information into related categories or broken up telephone or bank account numbers or so into hyphens.
In summary, STM is a stage of memory with limited capacity in which information- often stored in acoustic codes- is lost rapidly unless it is rehearsed. The capacity of STM can be expanded by increasing the amount of information in each chunk to be good place to store information for long periods of time. Such information must be transferred to long-term memory for more permanent storage.
C-Long-Term Memory:
It is the storehouse for information that must be kept for long periods of time.
Differences between STM and LTM;
They differ in four major ways:
The way in which information is recalled: Because the amount of information stored in the LTM is so vast, it has to be indexed, and we retrieve information from LTM using cues, as in using a call number to find a book in the library. The recall is either intentional act as- what was the name of the previous Dean, or an unintentional act as when hearing a particular song brings back memories of a lost love, while in STM we scan the entire contents of the memory when we are looking for a bit of information.
The form in which information is stored in memory: In STM information is stored in terms of the physical qualities of the experience (what we saw, did, tasted, touched, or heard), with a special emphasis on acoustic codes. While information is stored in LTM primarily in terms of its meaning, or semantic codes.
The reasons that forgetting occurs. In STM information that is not rehearsed or processed appears to drop out of the system, while information stored in LTM is actually appears to be permanent, and forgetting when occurred because we are unable to retrieve it for some reason, not because the memory is erased as in STM.
The physical location or sites of these functions in the brain. STM is primarily a function of the frontal lobes of the cerebral cortex, whereas information that are stored in LTM is first integrated in the hippocampus and then transferred to the areas of the cerebral cortex involved in language and perception for permanent storage.
Types of LTM:
Procedural memory; It is memory for skills and other procedures. Memories of how to ride, a bicycle, to cook, or to kiss are procedural memories.
Semantic memory; It is memory for meaning. When you remember what father is, what pudding is, and what the phrase '' peace of mind '' means, you are recalling meaning from long-term semantic memory.
Episodic memory; It is the kind of LTM that stores information about experiences that took place at specific times and in specific places.
The LTM mechanisms are apparently able to store procedural and semantic memories quite effectively, but LMT handles episodic information much less well. Declarative memory-referred to grouping semantic and episodic memories together, as they are easily described or declared in words, in contrast to procedural memory, which can be assessed only through performance and it is difficult, if not impossible, to describe verbally the experience, because they involve such skills as playing the guitar, which can be seen only when the task is performed.
Organization in LTM:
Organization is important in facilitating the retrieval of information from the vast amount stored in LTM. One way of organization is to group information into categories such as: animals, vegetables, names, and professions. When research participants memorize new list of items that could be categorized, they tend to recall them in related groups. Apparently, the words were stored in LTM according to organized categories. In addition, there is clear evidence that recall from LTM is better when we impose more organization on the information that is stored there. e.g. in a research by ( Brower and Clark,1969) when participants were asked to memorized 12 lists of 10 words, half of them were asked to memorize the words in any order and the other half to make up stories containing all the words in the list- to organize them into a single story. The group that organized the words into stories recalled an amazing 90% of the 12 lists of words, whereas the other group recalled only 15%.
The Organization of memory in LTD has been characterized as an associative network by some theorists. According to this view, memories are associated, or linked together, through experience. E.g. your experience forms links between that special song and memories of your summer vacation, or between algebra and that undesirable teacher. The operation of the associative network is explained by the spreading activation model, accordingly, we form links between various concepts and their characteristics based on our experience. When we asked a question, representations of the concepts or characteristics are activated, as when asked the question '' Is a canary a bird''. All features related to this bird become readily available and linked to answer the question. Also related items are readily memorized than unrelated items e.g. bread-butter in contrast to nurse-butter ,as the word butter was activated partially even before the word bread appeared on a screen in an experiment on memory.
Retrieval of Long-Term Memories:
Three ways of testing retrieval;
Recall method: Here you are asked to recall information with few, if any, cues; Whom did Bill Clinton defeat for the presidency of the United States in 1996?. This is a recall method of assessing your memory for that fact.
2-Recognition method: you are asked to recognize the correct information from among alternatives. The same question could be asked as a recognition question:
In 1966, Bill Clinton defeated----------------- for presidency of the United States.
a- Bob Dole b- George Bush c- Pat Buchanan d- Jimmy Carter
Generally, we can 'remember' more when tested by the recognition rather than the recall method, because recognition tasks provide more cues for retrieving information from long term memory.
3-Relearning (or saving) method: It is the most sensitive of all three of the methods of evaluating memory. In this method, you relearn previously memorized information. If the relearning takes less time than the original learning, then the information has been remembered in this sense. E.g. relearning a mathematical problem that you are unable to remember now.
Your enhanced ability to relearn the technique shows that the memory was never completely lost.
Serial Learning: Is another type of retrieval tasks, here the order in which we memorize a list is as important as the items in the list. The recall of items in the serial lists is often better for items at the beginning and end of the list than in the middle. This is called the serial position effect.
The ''Tip-of the Tongue'' Phenomenon. Referred to sudden block in recall. Studies suggest that about half of the things that we can't remember, but are the tip of our tongues, are recalled within a minute or so.
Level of Processing Model: It is an alternative to the stage model. Suggesting that the distinction between short-term and long-term memory is a matter of degree rather than separate stages. The durability of stored information depends on how well it is processed as it is being encoded for memory. Information will be kept only briefly if it's processed at a shallow level, but it will be kept much longer if it's processed at a deeper level. Thus, the differences between STM and LTM are not differences between two different memory systems operating according to different principles. Rather, these differences are the results of different levels of processing during the encoding process. And there is a continuum of levels of processing, ranging from very shallow to very deep, rather than just two types of storage (short and long). Shallow processing involves the encoding of superficial perceptual information, whereas deep processing encodes meaning. Deep processing also involves greater elaboration of memories during encoding phase than does shallow processing.
Elaboration- means creating more association between the new memory and existing memories. What is interesting about deep processing is that even superficial perceptual information can be richly elaborated, e.g. relating a new telephone number to existing memories about the person your calling ,particularly if you relate the new information to yourself.
Forgetting:
There are four major theories of forgetting;
Decay Theory
According to this theory, memories that are not used fade gradually over time as a result of disuse. It is unaccepted by most psychologists, as forgetting is more complicated than the mere fading of memory traces and involves factors other than time.
Interference Theory
This theory is based on a considerable evidence that forgetting in LTM does not occur because of passage of time but, rather, because other memories interfere with the retrieval of what you trying to recall, if other memories are similar to the one you are trying to remember.
Proactive interference- referred to interference built up by prior learning , while interference created by later learning as Retroactive interference. e.g. suppose one day, you meet two interesting persons each at a time, in a hotel, and told you their rooms numbers. If you forgot the room number of the person you met later, you are the victim of proactive interference by the number of the first person and the victim of retroactive interference if you forgot the number of the first person.
Schema Theory
First presented in 1932 by Sir Fredric Bartlett, the theory that is known today as schema theory suggests that information stored in LTM is not forgotten in the usual sense but sometimes is recalled in a distorted, incorrect manner. Schemas are beliefs, knowledge, and expectations. Long-term memories often become distorted because they change over time to become more consistent with our schemas. e.g. if you have a negative view on a person, you give negative information about him to the other and minimizing any positive aspect he has.The distortion of memories to fit our schemas does not occur gradually over time but occurs during the process of retrieval itself.
Theory of Motivated Forgetting:
Forgetting that is believed to be based on upsetting or threatening nature of the information that is forgotten. Freud suggested that we forget some information because it's threatening to us in some way. Freud believed that the conscious mind often dealt with unpleasant or dangerous information by pushing it into unconsciousness, by an act of repression.
Relationship between emotion and memory:
It is a complex relationship. Researches on relationship between emotional arousal and memory indicated that individuals are better able to recall words with positive emotional impact (such as kiss or prize) than words with negative emotional impact (such as disease or loss).Words with neutral emotional impact are recalled least. Memories of intensely negative events tend to be vivid but are often disorganized and confused. These vivid memories are called flashbulb memories.
Biological Basis of Memory
A great deal has been learned about memory in recent years through the study of the role of the brain in the storage and retrieval of information.
a- Synaptic theories of Memory:
It is obvious that some physical change must take place in the nervous system when we learn something new. This ''something'' that remains after learning is called engram by the early memory researcher-Karl Lashley. It is the biological basis of memory. It is the memory trace.
The synaptic theory stated many years ago by Canadian researcher Donald Hebb (1949) is still considered to provide an accurate model of the physiological processes responsible for learning and memory. According to Hebb, synaptic facilitation is the biological basis of learning and memory. Individual experiences result in unique patterns of neural activity, which ''reverberate'' through neural loops. This causes structural changes in the synapses to occur. These changes make firing in the loop more likely in the future. i.e. synapses become more efficient, or facilitated. Thus for Hebb, changes in the synapses are the biological basis of memory. This theory was confirmed in an experiment on sea snail by using stimulation and classical conditioning, The changes in synapses were studied by measuring the amount of neurotransmitter which was increased. For Hebb learning is remembered at synapse. Several studies give evidence that suggests that changes in synapses are based on changes in their proteins for LTM, but not STM.
b-Stages of Memory and the Brain:
The parts of the brain associated with different stages of memory include;
Visual information is first routed through the thalamus to the visual area of the cerebral cortex. This neural activity is the basis for the sensory register.
The information is then relayed to the frontal lobes, where it can be held in short-term memory.
Information that is stored in long-term memory is held in the hippocampus for weeks or months, and then transferred to the areas of the cerebral cortex near where it was originally processed for long term storage.
When we recall information from long-term memory, it is routed again to the frontal lobes, where it is held in short-term (or working) memory.
Memories for events associated with intense negative emotions (flashbulb memories) tend to be vivid but disorganized. Such events that create intense negative emotional arousal activate the amygdale, and its involvement tends to improve recall. This negative emotional arousal stimulates the release of the adrenal stress hormone, cortisol, which inhibits the hippocampus. Because the hippocampus organizes the elements of complex memories that are stored in different parts of the cortex, inhibition of the hippocampus appears to result in a lack of organization in emotionally charged memories, which may make distortions more likely.
c-Amnesia:
It refers to disorders of memory, which is of two types; 1-Anterograde Amnesia:
This is a disorder of memory characterized by an inability to consciously retrieve new information in LTM for events following a disorder or a trauma to the brain. STM is not affected and information retained for about 15 seconds, but patients can not retained or store any new information or knowledge and retrieve them. Anterograde amnesia usually does not affect the ability to acquire procedural memories but disrupts the ability to form new declarative memories.
The biological or brain structure responsible for this disorder is the hippocampus. Which is believed to govern the transfer of memories from STM to LTM. Damage to the hippocampus spares both new and old procedural memories but prevents the formation of new long-term declarative memories.
Anterograde amnesia can be caused by: brain tumors, lack of oxygen to the brain, damage to blood vessels in the brain, senility, and sever nutritional deficiencies. Also hard blow to the head can cause such amnesia temporarily.
Retrograde Amnesia:
It is opposite of anterograde amnesia. Individuals are unable to recall information from the past. They can not retrieve old long-term memories. Memory might be lost for a period of minutes, days, or even years.
It can be caused by disease or trauma to the brain, or highly stressful events.
Generally, most brain-damaged individuals with anterograde amnesia also experience retrograde amnesia for periods of days or weeks. This is common in Korsakoff's syndrome, caused by brain damage in hippocampus and mammillary bodies due thiamine deficiency in chronic alcoholism and other disorders.