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PSYCH 101 CHPT. 8

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Department
Psychology
Course
PSYC 101
Professor
Barbara Cox
Semester
Winter

Description
PSYC 101 007 CHPT.8 MEMORY I. Overview of Memory Like learning, memory can’t be measured directly. Again, we have to indirectly measure it based on performance. Early Understanding of Memory: Associative Models  Associationism- belief that memory results from mental connections between ideas and concepts  First systematically studied by Herman Ebbinghaus in the late 1800’s  Ebbinghaus memorized strings of nonsense syllables & tried to figure out the basic rules of memory  Used himself as the only subject, prolonged study over several years Memory & Information Processing  Starting in the ‘80s it become more popular to look at memory processes like a computer  Broke down memory into processes  Memory- the cognitive processes of encoding, storing & retrieving information  Encoding- process by which sensory info is converted into a form that can be used by the brain’s memory system  Storage- process of maintaining info in memory  Retrieval- active processes of locating and using the stored information  Active/latent distinction between retrieval of info  Donald Hebb used this distinction to suggest the brain remembered info in 2 different ways  Known as dual trace theory  Info in active state b/c of neurons firing continuously- feedback circuits of neurons  Repeated firing strengthened the synaptic efficiency of the circuit, leading to structural changes in the neurons involved  This structural change persists after the activity has ceased- latent structural state  The brain retains traces of an experience either in an active state or latent structural state  Richard Atkinson & Richard Shiffrin later proposed that memory takes 3 forms: 1. Sensory Memory-memory in which representations of the physical features of a stimulus are stored for very brief durations  Difficult to distinguish from act of perception  Corresponds to memory systems that retain active traces  Info contained here represents original stimulus fairly accurately & contains all or most of the info that has just been perceived 2. Short Term Memory- immediate memory for stimuli that have just been perceived  Limited both in terms of capacity (5-9, usually 7 chunks of info) and duration (less than 20 secs)  Remember the info by keeping it active, such as repeating it  Let the info become inactive, then might not remember it later  Unless info stored in long term memory, it will be lost forever 3. Long Term Memory- info is represented on a permanent or near permanent basis  Retains latent traces  Has no known limits, is relatively durable  Occurs b/c of physical changes that take place in the brain  Info here need not be continually rehearsed like in short term memory  Can retrieve info from here for future use  Implication that info flows from one type of memory to another called modal model of memory II. Sensory Memory  We become aware of sensory memory only when info is presented very briefly so that we can perceive its after- effects  Ex. thunderstorm at night provides an opportunity to become aware of visual sensory memory  When flash of lightening reveals a scene, we see things before we recognize them  2 most important forms: iconic (visual) & echoic (audio) memory Iconic Memory- a form of sensory memory that holds a brief visual image of a scene that has just been perceived  Aka visible persistence b/c representation is closely tied to perception  Sperling studied this form by flashing a set of 9 letters on the screen for 50 milliseconds  He then asked people to recall as many letters as they could- known as whole-report procedure  On average, they could remember on 4 or 5 letters, they saw more than that but image of the letters faded too quickly for people to identify them all  Sperling used the partial-report procedure to determine whether the capacity of iconic memory accounted for this limitation  Hebb sounded low, medium or high tone immediately after matrix disappeared  tone signaled 1 row to report  recall was almost perfect  when he delayed the tone signalling which row to remember, recall only 50%  Showed people could not report more than 5 letters not b/c they didn’t have enough time to view all the letters  When visual stimulus is presented for a brief flash, all the info is available for a short time & people can see and recall the info momentarily  BUT image of visual stimulus fades quickly from iconic memory  The people had to scan their iconic memory, identify each letter, & name it verbally  During this process, the letters were fading & the info becoming unreliable  Although their iconic memory contained all 9 letters, they had time to recognize & report only 4-5 before the mental image disappeared Echoic Memory- a form of sensory memory for sounds that have just been perceived  we hear individual sounds one at a time when we hear a word pronounced  we cannot identify the word until we have heard all the sounds  acoustical info must be stored temporarily until all the sounds have been received  Appears to operate similar to iconic memory III. Short Term or Working Memory Encoding of Information in the Short Term: Interaction with Long Term Memory  Sensory memory forms automatically, without attention or interpretation  Attention is needed to transfer information to short term memory  Information can also enter short term memory from long term memory  When performing a task, some info that we require to do it is available in our long term memory  This info is moved into short term memory & then recalled  So short term memory contains both new info & info retrieved from long term memory  Led to preference for the term working memory  Working Memory- memory for new info & info retrieved from long term memory  Represents our ability to remember what we have just perceived & to think about it in terms of what we know  A sort of behaviour that we use to maintain info over the short term Primacy and Recency Effects  Primacy effect- tendency to remember initial info  In memorization of a list of words, the effect is evidenced by better recall of words early in the list  Caused by words earlier in a list having the opportunity to be rehearsed more than others words later in the list  The rehearsal permits the beginning words in long term memory-> remembered better  Recency Effect- tendency to recall later info  In memorization of a list of words, the effect is evidenced by better recall of the last words in the list  Last words to be heard still in short term memory  Shows that memory follows predictable patterns & is dependent on the contributions of rehearsal & short term memory The Limits of Working Memory  Maintenance rehearsal- mental or verbal repetition of info  Allows info to remain in working memory longer than the usual 30 secs  Memory decays quickly if prevented from using maintenance rehearsal  Consider the following experiment:  Nonsense syllable presented  BUT, have to count backwards from 1,000 by sevens (i.e., 1014, 1007, 1000 … etc.)  The backward counting prevents rehearsal  Stimuli remain in working memory for less than 20 secs unless they are rehearsed  Petersons pointed out that working memory may be even more limited  Found that unexpected distractions seriously disrupted working memory  Most people found it hard to recall 3 letters after only 2 secs  Capacity of working memory: people can retain on average about 7 pieces of info in their short term memories  Chunking- process by which info is simplified by rules, which make it easily remembered once the rules are learned  Ex. Easier to remember sequence of letters “MBIASUAICIBF” when organize them into smaller chunks “ FBI CIA USA IBM”  Capacity for verbal material depends on how much meaning the info has  When items are related, we can store many more of them  Chain unrelated words together by imaging a story involving them to improve short term memory of those words Varieties of Working Memory  Working memory can contain a variety of sensory info & motor memories  Baddeley suggested that working memory consists of several components all coordinated by a “central executive” function  Phonological short term memory- short term memory for verbal info  Phonological coding involves both the auditory system of the brain (auditory association cortex) & the system that controls speech  People read the letters, encode them acoustically & remember them by rehearsing the letters as sounds  During this process, may easily make acoustic errors  Reflects a form of acoustical coding in working memory  Subvocal articulation prevents decay of phonological short term memory  Best neurological evidence for existence of phonological short term memory comes from a disorder called conduction aphasia  Conduction aphasia- inability to remember words that are heard, although they usually can be understood & responded to appropriately  Caused by damage to a region of the left parietal lobe (Wernicke’s & Broca’s areas)  b/c brain damage that produces this disorder disconnects regions of the brain involved in speech perception & production, perhaps the damage disrupts acoustical short term memory  making subvocal verbal rehearsal difficult or impossible  verbal info can be perceived by the visual system as well  we possess a working memory that contains visual info  obtained from immediate environment via our sense organs  or retrieved from long term memory  Much of what we see is familiar- visual working memory doesn’t have to encode details  Ex. our short term memory of a dog doesn’t need to store all its visual features, already have mental images of dogs in our long-term memory (prototype selected to fit the bill)  Degroot: chess experiment, showed experts and novices chessboards  If game in progress, experts could glance away from the board, repeat piece positions, novices could not  However, if the pieces were placed haphazardly on board, experts can’t repeat piece positions better than novice  Their short term memories for the positions depended on the organizational rules stored in long-term memory as a result of years playing chess  Humans can manipulate visual info in working memory  Shepard and Metzler drawings experiment: mental manipulation to rotate images to coincide with drawings  people accurate in judging if shapes are the same Loss of Information from Short Term Memory  Info is maintained in working memory as long as it is rehearsed  Anything that interferes with rehearsal leads to loss of short term info, possibly through decay  Metaphor: working memory is juggling, with greater skill or effort, more items can be juggled, unless a distraction occurs IV. Learning and Encoding in Long Term Memory  Once info successfully goes into long term memory, it remains stable The Consolidation Hypothesis  traditional view of memory- sensory and short-term memory represent info in its active stateresult of brain processes that keep the info active  Consolidation- process by which info in short-term memory changes to long-term memory (physical changes that occur in neurons in brain)  Consolidated info =long term memory,  rehearsal allows consolidation to occur, can also happen without awareness  Best evidence comes from events that disrupt brain functioning  Blow to head affects memory, disrupts the balance in ions surrounding brain cells- large metabolic changes  Dutch amateur boxers given standard tests for memory ability before and after a boxing match, compared to non-boxers who simply exercised- boxer scores showed significant impairments  Retrograde amnesia- severe case of injury causes loss of ability to retrieve memories of one’s past, particularly memories of episodic or autobiographical events, b/c of damage to the brain’s centres for consolidation  Retrograde amnesia- recent memories more strongly affected than older ones (less time to have had been consolidated=weaker) Consolidation and the “Genetic Action Potential”  Hebb’s learning concept- synaptic connections formed or strengthened  Consolidation of memory therefore involves synaptic structures, the synthesis of proteins  David Clayton- molecular activity of genes should be considered in information terms like action potential- “genomic action potential”  Immediate-early genes (IEG)- genes which can be activated, or induced, without the synthesis of proteinsthe first part of a chain triggered by events like an action potential  ex. birds use songs to identify other members of their species o calls are complex acoustically, learned when bird is young by listening to an adult tutor o song is then stored in memory and used, fine-tuned in adulthood o memory partly the result of a particular IEG with ZENK (song gene name) o Listening to birdsong increased genetic ZENK activity in adult birds The Levels of Processing Hypothesis  Previous assumptions:  All info gets into long-term memory only after passing through short-term memory  The most important factor determining whether a particular piece of info reaches long-term memory is time spent in short term memory  Craik and Lockhart: the act of rehearsal may effectively keep info in short-term memory but does not guarantee the establishment of long-term memories  Maintenance Rehearsal: the rote repetition of info; repeating a given item over and over again  Maintains info in short term memory, but does not necessarily result in lasting cha
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