[vinnomot] Humanism and Psychology: (Comp 8): Human Memory

Understanding Ourselves and Our Universe: How Psychology Can Turn the "Mysteries of Human Nature" into Useful Tools for Self Improvement and Success in Life

 

Part  8: The Three-Store Model of Human Memory

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When your brain leaps from forming only a few isolated connections  to forming a whole complex series of integrated connections, based not only on the unique qualities of that stimulus but also linking to all brain connections with qualities similar to that stimulus, you've made the leap from simple ideation (a single unique thought or memory) all the way to concept formation and conceptualization (integrated groups of thoughts or memories linked by common similarities)…… As was introduced earlier in this module, one's memory is absolutely indispensable to one's ability to normally perceive sensory information (as history is necessary for indispensable as memory of a nation). Without memory, one would be limited to genetically pre-programmed perceptual experiences, which are so simple as to make the world a meaningless place, just as History is the memory of a nation or country or humanity as a whole without with civilizaion cannot progress . If such an experience happened again, impoverished as it was, one would be incapable of recognizing it or communicating it to anyone else. However, what psychologists mean by memory is considerably different than the simple concept most people understand that term to mean. Human memory, once again in simplified form, has two basic functions: (1) to store coded information over time in unchanged form; and (2) to retrieve that information from storage when it's needed. A simple example is when we learn the answer ("Hobart") to a question ("What is the capital of Tasmania?"). We need to (1) store that answer correctly until we need it, and then (2) produce that answer when it's appropriate (and only when it's appropriate). Failure of either function means no memory. Compared to other animals, human memory is impressive, since we have the largest known memory capacity on earth. Compared to "perfection," however, we have remarkably inefficient memory systems, since very few memories are ever stored for significant periods of time without being changed to some degree, and too often we fail to retrieve needed memories as quickly and accurately as we'd like. ("What is Aunt Harriet's third husband's name?" "Tell me your phone number again?") So much, again, for that "image of a perfect maker" idea! Embedded within the neurophysiology of our sensory receptors, sensory transmitters, and our CNS there are three integrated but different memory functions. When stimulus information is first transduced and transmitted, the first memory store sensory memory (SM) begins to function. People who do not study psychology or human biology can live their whole lives unaware that they even have sensory memory, because it operates so quickly and automatically, and there is almost no way to make its functions conscious. In fact, in the ½-second or more it takes to concentrate on one's sensory memory, it has already finished its functions, or it has failed. Some people, however, occasionally report an almost instantaneous "sensory echo" to some stimuli, particularly with loud sounds or bright lights, which may well be sensory memory retrieval. Sensory memory's only function is to store a veridical (true, unprocessed) copy of a sensory stimulus called an icon (so raw and meaningless that we don't even call it "information" until it has undergone further processing), for approximately ¼-½ second. Any stimulus that attracts selective attention (i.e., on which we consciously or unconsciously focus our attention) goes on to short term memory. As we grow and develop, we supplement our basic genetically pre-programmed repertoire of salient stimuli (i.e., aspects of our environment that are adaptive to sense, like food odors when we're hungry or warmth when we're cold) by learning from experience what non-instinctive stimuli are adaptive to sense too (like money when we're poor or a friend's tone of voice indicating that they're upset). Sensory memory has a huge capacity; it can store a large number of stimuli simultaneously, but only for very short duration. If a sensory memory is not processed on within a second or two, it is lost forever, and we're never even aware that it was there. Thus, we routinely "sense" things with no sensory experience whatsoever to show for it. If we didn't have sensory memory, or if it routinely malfunctioned, we'd be stressed right into severe psychopathology due to being overstimulated by thousands of "important" but meaningless sensations every second of every day of our lives. Selective attention is a very important screening device to give our brains a manageable amount of sensory info to process at any one time. The tiny fraction of sensory memories that are selectively attended to are processed on into the second memory store, short term memory (STM). Unlike SM, we are well aware of our short term memory, and consciously use it every day to "hold information" we need to remember and/or want to use quickly. Note what you do the next time you're given a phone number; you'll "say it over and over to yourself" -- vocally or subvocally -- until you can use it or write it down for future reference. That is your STM at work. Short term memory is often called "working memory", because whenever we concentrate on something, in fact,  we're trying to remember it, we take this information from external stimuli or long term memory and "work on it" to bring it into STM. Unlike SM, STM lasts for approximately 15-30 seconds, but has a very small capacity (i.e., it can only store 7-9 different meaningful images at once). Just as stimulus icons are maintained or processed on into SM via selective attention, memory images in STM are maintained for longer periods of time and/or transferred into long term memory (LTM) by means of "rehearsal." There are two basic types of rehearsal that will successfully process STM images, but they differ enormously in their effect on our memory storage and how well we can retrieve that information later. Maintenance rehearsal is simply restimulating ourselves with the stimulus material over and over again (like rotely repeating a person's name or phone number several times in a row), but the long term memory image or engram it produces is a very singular, impoverished one, which is fairly easy to store (get into LTM) but quite difficult to retrieve (get out when we need to recall it). Maintenance rehearsal can form simple, one-to-one memories (like, "What is the capital of Tasmania? Hobart!"), but not the more complex memories that are more important to human IP. Elaborative rehearsal is the second means of processing STM images, but it produces much more easily stored engrams that are much easier to retrieve. Elaborative rehearsal means associating the new image with already learned information, and it can take many forms -- far too many to exhaustively review here. Three common methods of elaboration are to 1.  associate the new memory with similar, well-learned old memories (e.g, "Your name is Suggins? I have a favorite cousin named Suggins!") 2.  associate the new memory with other sensory images that are naturally and/or logically related to it (e.g., you won't forget the name of that delicious exotic fruit you tasted on vacation because you simultaneously learned its name along with its visual image, its taste, its smell, and its texture) 3.  synthesize novel sensory images into previously analyzed and learned groups of sub-images, which is called "chunking" (e.g., 11-digit long distance numbers would exceed our STM capacity for rehearsal if we didn't break it down into prefixes, area codes, and so on). If you remember phone numbers well, this chunking technique is why. The more thoroughly we learn something, the easier it is to chunk in the future. There are hundreds of "memory aid" systems (called mnemonics), any of which may help some people improve their memory for some kinds of information. But the three elaborative rehearsal techniques described above will always work for all normal people with all kinds of memories, because our brains and nervous systems are already genetically preprogrammed to receive, store, and retrieve information that way. (Yes, despite considerable everyday experience to the contrary, all people with an intact CNS organize, store, and retrieve their memories logically, because all normal brains are genetically organized in ways we call "logical." Sometimes people can and do behave illogically, but the reasons for that won't be addressed in this module.) STM memory information that is sufficiently rehearsed is processed on into the third memory store, long term memory (LTM). Very distinctively from either of the shorter memory brain range well into the trillions), and engram storage is also relatively permanent stores, LTM is extremely large in capacity (estimates of how many memory engrams can be stored in the human As was earlier stated, the two primary functions of LTM are to permanently store each memory in an unchanged form, and to efficiently retrieve that memory when it is needed. Most evidence indicates that engrams are stored associatively throughout most of the non-specialized areas of the brain. Just as selective attention is the key to successful processing through SM, and rehearsal is the key to successful processing through STM, categorization and organization by meaning seems to be the key to successful long term storage and retrieval in LTM. Recalling that new memory images enter the brain in the form of neural codes sent up the sensory transmission neurons from the sensory receptors, we can tentatively locate the three memory stores within the human CNS neurophysiology as follows: SM is likely a function of subcortical areas of the brain such as the thalamus STM is likely a cortical function of the brain's primary sensory reception and association areas (each of the 12 senses has its own genetically specialized sensory reception area in the brain) LTM is primarily a function of the cerebral cortex's general association areas (which are much larger, programmable areas spread throughout both of the two hemispheres and all four lobes of the brain) The point here is that when memory information enters the brain, the transmission neurons fire genetically pre-programmed groups of neurons called neural circuits. These circuits continue firing in the brain as long as rehearsal is going on. Each sensory reception circuit that fires will also fire at least one other sensory association circuit, depending on how the new material was rehearsed in STM. Rote rehearsal fires only a very few circuits -- perhaps only two (representing the memory image and the stimulus cue that came in with that image). For example, if you learn "Sally Smythe's phone number is 592-7654" by rote rehearsal, the only two LTM circuits that may be formed are "Sally Smythe's phone number" (the stimulus cue) and "592-7654" (the stimulus memory image). Two associated engrams = two sensory reception circuits + perhaps another two sensory association circuits = only 4 circuits altogether storing that new LTM memory. In the grand scheme of brain circuitry, that's a very tiny engram! (And as with some other human endeavors we can think of, size really is important here) If, instead, you learn exactly the same stimulus material by elaborative rehearsal in STM, a much larger number of sensory reception memory circuits are formed to store that material, as well as perhaps dozens of other sensory association circuits associated with those reception circuits. For example, using the three illustrative elaborations we used before, if when you STM rehearse Sally Smythe, you also picture how she looks, what her voice sounds like, and maybe what she was wearing and the aroma of the perfume she used (multisensory imaging), that's five sensory reception circuits formed for Sally Smythe, instead of just the one circuit with rote rehearsal. And if instead of just rotely rehearsing her phone number, you also chunk the prefix and last four numbers (using only two "slots" in STM instead of seven), and you note that 592 is the local prefix of other friends of yours, too, and that the 7654 numbers are in reverse sequence, and that you've previously memorized five other phone numbers that are in reverse sequence (associating the new material with logical patterns and also old memories), those elaborations will produce not two to four sensory reception circuits like rote rehearsal, but a total of 14 sensory reception circuits for the material you elaboratively rehearsed. Each of these 14 sensory reception circuits will in turn fire sensory association circuits with the same type of meaning, so those 14 circuits will associate with all your other LTM memory circuits for "pretty girls" and "clothes like Sally's" and "voices like Sally's" and "perfumes like Sally's" and "phone prefixes like Sally's" and "phone suffixes like Sally's", etc., etc. So just by elaborating on your STM rehearsal image, it would not be unusual to form dozens or even hundreds of associated circuits linked to "Sally's phone number is 592-7654" by common meanings. And that means that any one of the memories stored in all those circuits can be retrieved by stimulation of any other one of those circuits. When your brain leaps from forming only a few isolated circuits to forming a whole complex series of integrated circuits, based not only on the unique qualities of that stimulus but also linking to all brain circuits with qualities similar to that stimulus, you've made the leap from simple ideation (a single unique thought or memory) all the way to concept formation and conceptualization (integrated groups of thoughts or memories linked by common similarities). Likewise, the neurological organization underlying and operationally defining this huge difference in cognition has leaped from a few associated circuits to a whole complex of associated groups of circuits organized and linked by common meanings, called a neural network. To the immediate point, long term memories that are rotely rehearsed can only be retrieved by producing the stimulus cue with which they were associated when they were first learned. Thus, to retrieve the example's information, one would likely have to hear, "What is Sally Smythe's phone number?" in order to reliably retrieve the engram "592-7654". Otherwise, it would likely be "forgotten" if one just tried to recall it "cold", with no stimulus cues, "from memory." Elaboratively rehearsed engrams, however, can be retrieved using any of the learned elaborations, or using any of the other network associations formed in LTM. Thus, "pretty girls," "girls named Sally," or a whiff of Sally's perfume, or any reverse sequential phone number, or dialing up a friend with the 592 phone prefix, or seeing 592 on a license plate, etc., could all retrieve the memory of Sally Smythe's phone number. And every instance of recalling Sally's phone number, even when you're not trying to, constitutes another rehearsal, which makes that LTM engram even stronger; i.e., longer lasting, and better organized, and easier to retrieve. Such an external stimulus cue or internal idea that produces other memory associations (i.e., retrieves other memory engrams) is called a memory hook. Every hook that goes in with a new memory also provides a means for retrieving that memory, and the more hooks a memory forms in the brain, the faster and easier it will be to recall that memory when you need it. A final detail about how human memory works is the perhaps obvious one that not all long term memories are created equal. One method of classifying the qualitative differences in the "depth and breadth" of memories is the following four-type system: 1.  The least qualitative degree of memory is called relearning, and is so impoverished in content that one cannot even use that type of memory consciously. (It can only be demonstrated under lab conditions.) 2.  The second type is recognition: the ability to tell something familiar from something novel. (This is the basis of multiple-choice tests, by the way, and is a major reason such tests don't tell us much about learning!) 3.  The third type is recall, which is a simple one-to-one correspondence memory (what most of us commonly mean by the term "memory"). 4.  The fourth, and by far the most complex and complete form of memory is called redintegration. Redintegrative memories are multi-modal -- which means they involve several different senses -- and are heavily laden with emotions. Here are some examples of these four types of memory and one's high school prom: If you're taking a memory test in a lab, and you relearn a particular piece of music (that was played at your senior prom) significantly faster than totally novel music you've never heard before, that's relearning. (Note that if you were asked in advance if you'd ever heard that music before, you'd honestly answer, "No!") If you heard a different, better-remembered piece of music from your prom, but you couldn't remember what it was, or where you'd heard it before, that's recognition. If you heard a still better-remembered piece of music from your prom, and could say what it was, where you heard it, and maybe sing the words, that's recall. If someone just mentioned a still better-remembered piece of music from your prom, and you are suddenly "back at the prom" and can see and hear many aspects of the prom, and smell your date's cologne, and even "re-enjoy" the event, that's redintegrative memory. Routinely thinking and remembering using a few neural circuits (simple ideas) versus thinking and remembering using many neural circuits organized by meaning into neural networks (complex concepts) also has profound implications for one's cognitive abilities such as one's abilities to learn, remember learned material, and think critically or creatively, as well as ultimately one's intelligence (which is the single most important tool humans use to adapt, and accounts for most of the difference among a person merely surviving vs. coping vs. succeeding vs. excelling in life). For now, as that great humanist psychologist, Porky Pig, says, "The-the, the-the, the-the, that's all for now, folks!"

 

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