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Sensory Memory.doc

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Christopher Anderson

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Sensory Memory ● not aware – only when presented briefly ● have sensory memory for every modality – 2 main: iconic (visual) and echoic (auditory) Iconic Memory ● iconic memory – sensory memory that holds brief visual image of scene that has just been perceived; also known as visible persistence ● Sperling – presented visual images through tachistoscope at rate of 9 letters on screen for 50 milliseconds  on average, person could remember 4 or 5 but insisted that for brief time could see more but images faded to fast to see all  also used partial report procedure to determine whether capacity of iconic memory accounted for this limitation ■ asked people to name letters in only one horizontal row indicated by a tone after letters disappeared ■ able to repeat letters with perfect accuracy – iconic memory had capacity for all 9  if delay of tone was longer than 1 second people could onyl relay 50%  could not recall all 9 because had faded from memory Echoic Memory ● echoic memory – sensory memory for sounds that have just been perceived ● necessary for comprehending sound, particularly those that constitute speech – cannot identify word until we have heard whole sound so accoustical information must be stored temporarliy until all sounds have been received ● evidence from partial reporting shows that it lasts less than 4 seconds Short-Term or Working Memory Encoding of Information: Interaction with Long-Term Memory ● information can enter st memory from sensory of lt memory ● working memory – memory for new information and information retrieved from long-term memory; same as st memory  represents behaviour that takes place inside our head – represents our ability to remember what we have just perceived and to think about it in terms of what we already know Primacy and Recency Effects ● free-recall task – remember what you can of information that was just given to you ● primacy effect – tendency to remember initial information due to opportunity for rehearsal which causes them to be stored in lt memory ● recency effect – tendency to remember later information due to fact that they are last to be rehearsed so are still in st memory  pointed out by Atkinson and Shiffrin Limits of Working Memory ● Llyod and Margaret Peterson – presented people with stimuli composed of 3 consonants: JRG  people recalled info 30 seconds later  when made to count backwards from 3-4 digit numbers consonants were only accesible for a few seconds and dropped to zero after 15-18 seconds ● stimuli remain in st memory for 20 seconds unless rehearsed ● Miller – the magical number 7 plus or minu 2: people can retain on average 7+or- 2 pieces of information  chunking – process by which information is simplified by rules, which make it easily remembered once rules are learned ● can remember more if information can be organized into more meaningful sequence ● McNamara and Scott – taught people to chain unrelated words together as they listened to them – imagined story involving those words Varieties of Working Memory ● Phonological Working Memory: ● phonological short-term memory – short term memory for verbal information (whether presented visually or accoustically) ● Conrad – showed how quickly visually presented information becomes encoded acoustically  briefly showed people lists of 6 letters and then asked them to write letters  saw letters visually but when made errors, they were accoustical (V vs. B)  shows that words were encoded acoustically ● phonological memory may be produced by activity in auditory system by circuits of neurons in auditory association cortex ● subvocal articulation – unvoiced speech utterance ● although no actual movement may occur, is possible activity occurs in neural circuits that control speech ● when we invision something in our minds It is caused by activity in neurons in visual association cortex ● voice in head is probably from activity of neurons in motor association cortex ● Conrad – attempted to determine whether subvocal articulation played role in phonological working memory  study on deaf children (could not confuse letters because of their sounds)  children who made accoustical errors were ones who were rated as best speakers by teachers  deaf children who could speak best encoded letters in terms of movements they would make to pronounce them  clear evidence for articulatory code in working memory ● people may use acoustical and articulatory coding – simulatenously say word and feel themselves say it in head ● phonological code stored in lt memory also might help to strengthen rehearsed information ● conduction aphasia is best evidence for existence of phonoligcal st memory ● conduction aphasia – inability to remember words that are heard, although they usually can be understood and responded to appropriately; caused by damage to the connection between Wernicke's and Broca's - deficit in phonological working memory; might disrupt acoustical st memory by making such subvocal verbal rehearsal difficult or impossible ● Visual Working Memory: ● possess working memory that contains visual information either obtained from immediate environment by means of sense organs or retrieved from lt memory ● does not encode all details – find prototype in lt memory ● DeGroot – showed chessboards to expert players and to novices and if position of pieces represented game in progress, experts could glance at board for a few seconds and then look away and report position of each piece but novices could not; experts could also recognize immediately if positions were placed haphazardly  st memories for positions depended on organizational rules stored in lt memory as result of years of chess playing ● Gzowski – found similar pattern in Gretzsky's hockey playing ● have ability to manipulate visual information in working memory ● Shepard and Metzler – presented people with pairs of drawings that could be perceived as 3D constructions of cubes and found people could accurately judge if pairs were same shape even if rotated; were able to do so in head and ones that were more rotated, took longer to judge ● Loss of Information from ST Memory: ● st memory information controls behaviour and changes lt memory ● can decay but rehearsal refreshes it – but mostly due to displacement ● Waugh and Norman – heard lists of 16 digits where last digit was accompanied by tone and called probe digit – when people heard it they had to think back to last occurence of same digit that tell which digit followed that one; distance between target and probe was 1-12 items  critical variable was number of items, not time that elapsed – shows that new information displaces old information in st memory  also showed decayed if slow and a lot of digits were in between – but less of an effect ● St memory is encoded according to previously learned rules and information in LT memory determines nature of encoding Learnend Encoding in Long Term Memory ● perceptual memories involve alterations in circuits of neurons in sensory association cortex of brain, visual memories in visual association cortex, auditory in auditory association cortex, motor memories in motor association cortex in frontal lobes ● memories that involve combinations of perceptual information involve establishment of different connections between different regions of association cortex ● learning to perform particular behaviour involves establishing connections between appropriate regions of sensory and motor cortexes ● memory – inovles active and passive processes The Consolidation Hypothesis ● traditional view of memory is that it consists of 2 stage process: consolidation ● consolidation – process by which information in st memory is transferred to lt memory, presumably because of physical changes that occur in neurons in brain ● st memory consists of activity of neurons that encodes information received from sense organs and once acitibity subsides information is forgotten but through rehearsal activity can be sustained and if enough time passes activity causes structural change – permanent and solid; responsible for lt memory ● best evidence for this comes from events that dirsupt brain functioning ● retrograde amnesia – loss of ability to retrieve memories of one's past, particularly episodic or autobiographical, that occured just before episode  “closed-head injury” - brain bumps on inside of skull ● hypothesis assertions:  st and lt memory are physiologically different  all information gets into lt only after passing through st  most important factor determinig whether paritcular piece of information reaches lt memory is amount of time it spends in st memory The Levels of Processing Hypothesis ● Craik and Lockhart – pointed out that act of rehearsal may effectively keep information in st memory but does not necessarily result in establishment of lt memories  suggested that people engage in 2 types of rehearsal: maintenace rehearsal and elaborative rehearsal ● maintenance rehearsal – rote repetition of verbal information; repeating a given item over and over again; serves to maintain information in st memory but not necessarily resulting in lasting changes ● elaborate rehearsal – preocessing information on meaningful level, such as forming associations, attending to meaning of material, thinking about it, etc. ● Craik and Tulving – demonstrated effectiveness of elaboration in remembering by giving people set of cards containing printed sequence including missing words denoted by blank line and found that participants were twice as likely to remember sentence if word was of medium or high complexity  suggest that memory is more effectively established if item is presented in rich contex ● Craik and Lockhart – proposed framework for understanding process by which information enters lt memory: suggest that memory is by-product of perceptual analysis  central processor can analyze sensory information on several different levels that are hierarchically arranged from shallow (superficial) to deep (complex)  person can control level of analysis by paying attention to different features of stimulus ● shallow processing – analysis of superficial characteristics of stimulus, such as size or shape; example of this processing is maintenance rehearsal ● deep processing – analysis of complex characteristics of stimulus, such as its meaning or relationship to other stimuli (semantic features); example of this process is elaborative rehearsal – leads to better retention Knowledge, Encoding, and Learning ● how we encode information affects our ability to remember it later – paying attention to it and making it meaningful ● Automatic vs Effortful Processing:  effortful processing - practicing or rehearsing information (deep or shallow)  automatic processing – formation of memories of events and experiences with little or no attention or effort ■ information that is automatically processed includes frequency, time and place ● Encoding Specificity:  encoding specificity – principle that how we encode information determines our ability to reitve it later  Dooling and Lachman – found that people who were told title of hard to read passages remembered information much better than if they heard it after  time to make information meaningful is during encoding Criticism of Levels of Processing Hypothesis: ● term depth is metaphor, no defined distinction between shallow and deep processing ● research cannot control depth to which person processes information ● can retain information that relates to shallow processing – answer to question on page of notes written Improving Long-Term Memory through Mnemonics ● mnemonic systems – special technique or stratgey consciously employed in an attempt to improve memory ● Method of Loci:  method of loci – mnemonic system where items to be remembered are mentally associated with specific physical locations or landmarks ● Peg-Word Method:  peg-word method – mnemonic system in which items to be remembered are associated with set of mental pegs that one already has in memory, such as key words of a rhyme ● Narrative Stories and Songs:  narrative – mnemonic system in which items to be remembered are linked together by a story  Bower and Clark – showed people were able to remeber 120 words when told how to create story from them  Wallace – found people who learned words to sung ballad, rather than spoken, much more quickly  Kilgour, Jakobson and Cuddy – found that rate of words affected ability to remember, not whether sung or not  song slows rate so you can remember it better The Organization of Long-Term Memory ● consolidation is not a simple, passive process – many investigators believe that lt memory consists of more than pool of information – see it as organized into different systems where different kinds of information are encoded differently and stored in different ways, in response to evolutionary pressure Episodic and Semantic Memory ● lt memory contains more than exact records of sensory information that has been perceived – also contains information that has been transformed and organized in terms of meaning ● Sachs – showed that as memory of verbal material gets older, specific sensory information becomes less important that specific words  had people read passage and then say whether sentence (comparison sentence) was same sentence (test sentence) – as more syllables passed people could not remember specific words and sentences but did not get meaning wrong  form dissapears faster than meaning ● lead to suggestion that there are 2 types of lt memory – episodic and semantic ● episodic memory – type of lt memory that serves as record of life experience  autobiographical – consists of things we have done, seen, heard, felt, tasted and are tired to particular contexts ● semantic memory – type of lt memory that contains data, facts, and other information, including vocabulary  academic ● two interact together – remember most recent episode to aid semantic ● distinction reflects fact that we make use of different things we have learned but might just be different information stored in same system ● evidence comes form K.C. - man who cannot remember episodic information
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