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Textbook Notes Short Term and Working Memory.docx

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University of Toronto Mississauga
Christine Burton

Short Term and Working Memory Memory  Process involved in retaining, retrieving and using information about stimuli, images, events, ideas and skills after the original information is no longer present  Parts of the temporal lobe are important for forming new memories—if destroyed the person only lives within the most recent memory of 1-2 minutes and forgets everything else Atkinson and Shiffrin’s model of memory  Called the modal model of memory b/c it included many features of memory models that were being proposed in 1960s  Stages in the model are called the structural features of the model; three structural features 1. Sensory memory—first stage that holds all incoming information for seconds 2. STM—holds 5-7 items for 15-30 seconds 3. LTM—holds large information for years/decades  Memory system also has control processes which are active processes that can be controlled by the person and may differ from one task to another (eg) rehearsal- maintaining information in STM and encoding-storing information in LTM Sensory memory  Retention of the effects of sensory stimulation for short periods of time  Persistent of vision is the retention perception of light in your mind—when a sparkler is waved in the air, there is a trail of light. This trail of light is not created by the sparkler itself but is a creation of the mind which holds the perception of the sparkler’s light for few seconds Sperling’s experiment: measuring the capacity and duration of the sensory memory  Wondered how much information ppl can take in from a presented stimuli Experiment: Showed the participants an array of letters for 50 milliseconds and asked them to remember and report back as many of the letters as possible from the whole array. This was called the whole report method because participants were asked to report as many letter from the whole array of letters, only remembered 4.5 out of 12 letters on avg. He concluded that participants only saw 4.5 letters out of 12 due to the brief exposure time, and also their perception faded rapidly as they were reporting back the letters, that they forgot the rest of the letters on the matrix Made the partial report method to determine which two possibilities from the above is correct. He trained ppl to report certain rows when they hear a different sound pitch and cued the sound after the letters were shown. The participants were able to remember 3.3 out of 4 letters in that row. He concluded that because participants saw an average of 82% of the letters no matter which row was cued, immediately after the display was shown participants saw an average of 82% of letters on the whole display (because in order to remember which row is associated with what sound, they had to remember the row and the other rows that weren’t associated with the sound) and weren’t able to report all of the letters b/c the memory faded quickly as initial letters were being reported He did another experiment to determine the time course for the fading and made a delayed partial report method where the cue tones were delayed after the letters were presented. Results showed that due to this participants only reported more than 1 letter in a row for three rows—equivalent to the letters reported in whole report method Sperling concluded that short lived sensory memory registers all of the information that hits our visual receptors but that this information fades within less than a second—called iconic memory and corresponds to the sensory memory stage of Atkinson and Shiffrin’s model. Other research shows that sound also persist in the mind called echoic memory **sensory memory can hold lots of information (large capacity) but only holds that information for fraction of a second (small duration) Sensory memory good for: collection info to be processed, holding info while processing is going on and filling in the blanks when stimulation is caused STM  Stores small amounts of info for brief period of time  Peterson and Peterson experiment of Recall asks what is the duration of STM Experiment: Showed participants 3 letters and 2digit numbers on each trial, and asked them to remember the letters and when they hear/see the digits they should repeat it and count backwards by 3s. when they hear recall participants were expected to report the letters back As time increased they only remembered 12% of the letters and inferred that due to decay participants forgot the letters. In the first trial after the 3 sec and 18 sec delay there was little difference in the number of letters they recalled, as compared to all of the trials. Keppel and Underwood said a drop off in memory was due not to decay of memory trace but by proactive interference—interference that occurs when info that was learned interferes with learning new info. Keppel and Underwood said that proactive interference was what caused the decrease in memory observed in later trials b/c previously learned info was interfering with new letters What is the capacity of STM?  One measure of capacity of STM is provided by the digit span; typical span is between 5- 8 digits  Avg capacity of STM according to digit span is 5-9 items; suggested by Miller’s paper The Magical Number Seven, Plus or Minus Two  Recent measures of STM set capacity at 4 items; based on results of experiments by Luck and Vogel Luck and Vogel’s Experiment  Flashed two different arrays of coloured squares to participants separated by a brief delay and the task was to determine if the second array was diff from first  Results showed that performance was perfect when there were 1 to 3 squares in the arrays, but the performance decreased when there were 4 or more squares  Concluded that participants were able to retain 4 items in their STM How is it possible to hold many more items in some situations as when words are arranged in a sentence? Answer proposed by Miller who introduced the idea of chunking in his 7± 2 paper Miller and Chunking  Small units like words can be combined into larger meaningful units like phrases, sentences, paragraphs  A chunk has been defined as a collection of elements that are associated with one another but are weakly associated with elements in other chunks  Chunking w.r.t meaning increases our ability to hold information in STM  We can recall sequence of 5-8 unrelated words but arranging the words to form a meaningful sentence so words are strong associated with each other increases the memory span to 20 words or more  Chunking allows limited capacity STM to deal with large amount of information, such as chunking letters into words How is information coded in STM? 1. Auditory coding 2. Visual coding 3. Semantic coding Auditory coding  Representing items in STM based on their sound  Conrad’s experiment participants saw a number of letters flash on screen and were asked to write down the letters in the order they were presented  Errors were made when they misidentified the letter as another letter that sounded the same, even though letters were shown to them the letter mistakes were made by the sound of the letters  Concluded that code for STM is auditory (based on sound of stimulus) rather than visual (based on the appearance of stimulus) Visual coding  Representing items visually  Remember more due to chunking Semantic coding  Representing items in terms of their meaning  Wickens and coworkers did an experiment where the categories were fruits and professions and the participants were shown names of 3 fruits on each trial for up to 4 trials and asked to remember, count backwards and then recall  Results show that proactive interference by the previous memorization of fruit names caused the recall to drop after each trial  When the professions were presented in the same manner, the results were the same but on the 4 trial fruit names were asked to recall and there was no proactive interference because it was a different category, this effect is called release from proactive interference  STM described as short term storage mechanism, involved in the transfer of information to and from LTM, needed for active processes such as to understand conversations Working Memory  Limited capacity system for temporary storage and manipulation of information for complex tasks such as comprehension, learning and reasoning Working memory differs from STM in two ways: 1. STM is concerned with mainly storing information for brief periods of time (remembering phone #) whereas WM is concerned with the manipulation of information that occurs during complex cognition (remembering #s while reading a paragraph) 2. STM has a single component whereas WM consists of many components  Working memory is not only concerned with how info is stored but how that info is manipulated in various cognition tasks  It does the manipulation of info through three components: 1. Phonological loop 2. Visuospatial sketchpad 3. Central executive Phonological loop  2 components: phonological store that has limited capacity and holds info for few sec and the articulatory rehearsal process which is rehearsal that keeps items in phonological store from decaying  (eg.) remembering phone #, person’s name Phonological similarity effect: confusion of letters/words that sound similar refer to Conrad’s experiment that in memory test ppl confuse similar sounding letters, support for auditory coding in STM Word length effect: harder to remember longer words because it takes longer to rehearse the long words and to produce them during recall Articulatory suppression: person prevented from rehearsing items by repeating irrelevant sounds, this repetitio
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