Psych Exam 2 STM - Short-Term Memory STM • What is the...

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Unformatted text preview: Short-Term Memory STM • What is the duration of STM? • How much information can STM hold? • How is information coded in STM? Duration of STM • Brown (1958); Peterson & Peterson (1959) Studied a 3 item list, then counted backwards from a certain number then were asked to recall list. After how much time were they able to recall list – Asked people to study three letters – Then given a # to count backwards by threes (for 3-18 sec) • Prevents rehearsal – Recall letters Brown (1958); Peterson & Peterson (1959) • Results: – Recall declined rapidly (virtually none after 18 sec) After 18 seconds the info was lost. Duration of STM without rehearsal is about 15-20 seconds-Decay: Information is lost without effort and is forgotten Oveall avg performance • Conclusion: – Duration of STM without ________ is about ________ seconds • Decay? 1 Short-Term Memory Keppel & Underwood (1962) • Results: – No forgetting on the first trial of the Brown-Peterson task, even with 18 sec of counting -Instead of decay this task is measuring proactive interference.(what you learned previously interferes with what you are trying to learn) • Conclusion: – Instead of decay, this task is measuring _____________ _____________ Release from PI • Wickens et al. (1976) – Gave people 3 trials of Brown-Peterson task, where the 3 items belonged to the same semantic category – On 4th trial, saw a different category ("fruit") Wickens et al. (1976) PI is reduced when semantic category is changed • Results: – PI is reduced when _______________ is changed • Conclusion: – PI occurs in BrownPeterson task but can be released 2 Short-Term Memory Capacity of STM • Digit span – the number of digits that can be correctly recalled in order – Listen to each list of numbers, and then recall them in order: Keep making longer strings of digits and when you can no longer recall the string correctly the last one you recalled correctly is your digit span Capacity of STM • Miller (1956) – Proposed a limit of 7 + 2 (5-9) items • Other researchers have suggested a limit of 4 items using other tasks • In any case, how is it possible to hold many more items under some circumstances? Chunking • Miller (1956) – Small units can be combined into larger meaningful units – Chunk: Larger meaningful unit is a chunk Associating chunks with something meaningful uses LTM which helps overcome STM and helps us recall easier. • Collection of elements that are strongly associated with one another B V S M T A U I vs. T V U S A I B M – Chunking explains how we sometimes “overcome” STM’s limited capacity, using LTM 3 Short-Term Memory Chunking • Chunking can be used to demonstrate exceptional memory (Ericsson et al., 1980) – S.F.: • prior to practice, digit span = 7 • after two years of practice, digit span = 79 • used his extensive knowledge about longdistance running to do chunking, e.g., “2942” • Not a perfect strategy avg college student with avg digit span of 7 and for 2 years he practiced recall digit spans by using his knowledge of running and time for chunking. After 2 years he had a digit span of 79. Not perfect because if it had numbers that would be invalid time(ex: 69min?) he could not chunk easily and could not recall – Rajan: • http://www.learner.org/vod/vod_window.html?pi d=1588 Chunking via chess • Chase and Simon (1973) – Looked at memory of chess pieces on a board for chess masters and beginning chess players – Briefly presented pieces positioned for a real chess game or randomly positioned – Asked people to reproduce these arrangements Chase & Simon (1973) • Results: Place pieces in normal chess patterns and again in random chess patterns that doesn't make sense for chess. The chess masters' advantage for recalling disappeared when the pieces were placed randomly because they could not chunk • Conclusion: – Chess master’s advantage is due to grouping the pieces into meaningful chunks 4 Short-Term Memory Coding in STM • Auditory coding: – Wickelgren (1965) • Lists presented auditorily – Conrad (1964) • Lists presented visually – Results: • People made errors based on similar-sounding items (recall “S” instead of “F”), not similar looking items (don’t recall “E” instead of “F”) Coding in STM • Visual coding coding- way information is presented mentally (how does information in STM look?) -Wickelgreen believed it was auditorily because he presented letters from a tape recorder and made mistakes based on what the letters sound like. -Conrad believed it was visually but presented letters visually and people made mistakes based on letters sounding familiar even though the look different People were able to recall about 9 black squares before making mistakes. Creates convergent ideas about how we store info in STM and that it may be visual as well – Della Sala et al. (1999) • Presented a matrix with black and white squares for 3 sec: • Given a blank matrix, could reproduce patterns even though matrix is not easily represented in sounds. Coding in STM Semantic coding- storing meaning of info not just sounds and appearance • Semantic coding – Wickens et al. (1976) 5 ...
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