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Chapter 4

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Psychology 2135A/B
Ruby Nadler

Chapter 4: Short-Term Working Memory 10/16/2012 10:34:00 AM George Miller: “The Magical Number 7” FORGETTING Rate of Forgetting Peterson and Peterson study: tested undergrads on their ability to remember 3 consonants over a short retention interval. E.g. subject heard the letters CHJ followed by the number 506. They would then count backward until a light presented, which was a signal for recalling the three consonants (the counting down from 506 by 3s disabled any verbal rehearsal). The light went on between 3-18 sec after the subjects began counting.  Results: probability of a correct recall declined rapidly over the 18- second retention interval. o Implies we must rehearse verbal info to keep it available in STM. o Good side about putting a phone number in STM rather than LTM: Harder to retrieve the few numbers that you actually regularly dial. Decay versus Interference Is the loss of info from STM caused by decay or interference? Interference theory: memory for other material or the performance of another task interferes with memory and causes forgetting. Decay theory: info is spontaneously lost over time, even when there is no interference from other material. If memory decays over time, the amt of recall should be determined by the length of the retention interval. If memory is disrupted by interference, then recall should be determined by the number of interfering items. Waugh and Norman: tested whether the loss of info from STM is caused by decay or interference. - presented lists of 16 single digits. The last digit in every list occurred. The task was to report the digit that had followed the probe digit. They varied the # of interfering items by varying the location of test digit in the list. (many interfering items if test item occurred early in the list, and only a few if the test item occurred late in the list. They also tested the rate of pres, to see if the prob of recalling the test difgit would be influenced by the length of the retention interval.  Pres digits either 1 or 4 digits per second. Result: the rate of pres had little affect.  Memory is only slightly better for the shorter retention interval. The prob. Of recall declines rapidly as the number of interfering items increases. Therefore, W and N’s findings suggest: Interference, rather than decay, is the primary cause of forgetting. Although some decay may occur, the amt of forgetting caused by decay is way less than the amt caused by interference. Main Point: Interference is the chief cause of forgetting! Release from Proactive Interference  Means how interference can be reduced by decreasing the similarly among items. Proactive: forgetting that occurs because of interference from material encountered BEFORE learning. Retroactive: forgetting that occurs… material encountered AFTER learning. Release from P I will occur by having information be dissimilar from earlier material. Reduction of interference thru appropriate sequencing can partly compensate for the rapid forgetting from STM. CAPACITY The Magic Number 7 Memory span task: the # of correct items that people can immediately recall from a sequence of items. Magic #7 also in an absolute judgment task: identifying stims that vary along a single, sensory, continuum (e.g. varying by loudness, pitch, intensity) Subject’s task is to learn to identify each stim (diff levels of loudness for e.g.) by assigning the correct label (1 being softest, 7 loudest) The limitation was caused by the inability to keep more than about 7 sensory values available in STM cuz of its limited capacity. The upper limit (7 +-2) of absolute j experiments corresponds very well with the upper limit of memory span tasks! Miller: putting stuff in chunks helps memory Chunks: a cluster of items that has been stored as a unit in LTM (e.g. FBI, HMV, ACC) Miller: The capacity of STM should be measured in chunks rather than in individual items. Individual Differences in Chunking Chunking relating to how chess players reproduce the pieces on a chessboard. This study was done by de Groot a Dutch psychologist. Main conclusion of the study: differences in skill among novice and master players is from diffs in perception and memory as opposed to how they planned their moves.  Master players depended on their ability to code the pieces into familiar groups. o When the players viewed pieces that were placed randomly on the board, the master players no longer had an advantage over the weaker players, and the two groups performed about the same.  Chase and Simon did a similar test: identified chunks that presumably produced the superior coding ability of master players o Result: Obvee masters better cuz they had more chunks and more pieces (chess pieces) per chunk. o ALSO… the estimated # of chunks across the 3 skill levels are at that 7 range. Instructional Implications Sweller’s cognitive load theory (includes redundancy effect, split attention effect, expertise reversal effect, etc): our efforts to combine information can result in cognitive overload – too much information for our STM to manage.  Can result from a split attention effect: occurs when ppl must divide their attention b/t 2 sources, such as instructions and the physical objects. o To avoid this effect, physically integrate the info. E.g. steps with diagrams so that the reader does not have to continuously switch attention b/t 2 sources. Sweller and Chandler’s experiment: two groups: Group 1 received standard instructions and could apply them to a physical thing. Group 2 received MODIFIED instructions (steps as well as diagrams)  This instruction proved most effective If for instance Group 2 received modified instructions as well as the physical apparatus, Sweller and Chandler proposed they would suffer cog overload cuz of the redundancy effect: if equivalent info is provided twice, then the added info simply provides MORE rather than new, information. It would increase time of completing task too. Result was that if Group 2 also got physical thing, they would perform the same as those in Group 1. Expertise reversal effect: instruction that may reduce cognitive load for a novice, may actually increase cognitive load for an expert.  E.g. adding text to a diagram will increase the load for the expert if he/she can understand the diagram already w/o the text. MEMORY CODES Argument that acoustic (speech based) codes are the predominant codes in STM, and that semantic (meaning based) codes are the predominant codes in LTM. Acoustic Codes and the Rehearsal 2 separate verbal-processing rates influence a person’s memory span.  1) The speed at which a person can pronounce the items on the list used to test the memory span  2) The speed at which a person can retrieve the items from STM. Both rates determine how many items a person can keep active in STM. Cowan’s exp: students asked to recall strings of digits.  Pronunciation rates measured by asking students to count from 1- 10 as quick as can be.  Retrieval rates measured by seeing the amt of time b/t digits as students attempted to recall the items during the memory span task.  Results: both pronunciation rates and retrieval rates are correlated with memory span BUT they do not correlate with each other! Acoustic confusion: an error that sounds like the correct answer. It is very easy for acoustic confusions to occur when all letters in a sequence sound alike. They occur often in STM tasks. Phoneme: any of the basic sounds of a language that are combined to form speech. (e.g. the letter C (“se”) ) The letter C has two components – namely, the s and e sounds. These are the basic sounds of the English language.  Each pronunciation is represented by a diff phoneme Phonemes can account for acoustic confusions cuz words that sound alike usually have some phonemes in common. Laughery’s assumption: each of the auditory components representing an item can be independently forgotten – that if a name consists of two phonemes for e.., a person might remember one phoneme but not the other. Easy to mix up letters cuz its
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