Short-term memory

Short-term memory

1. Modal Model of Memory

   • integrated system; includes many of the features of memory models that were being proposed in the 1960s
   • became extremely influential 
   • shaped research on memory for many years 
   • Atkinson and Shiffrin (1968)
   • structural features
     • sensory memory
       • initial stage that HOLDS ALL INCOMING INFORMATION for seconds or fractions of a second 
       • all info that hits SENSORY RECEPTORS 
       • retention of the effects of SENSORY INFORMATION 
       • persistence of vision
         • the retention of the perception of light in your mind 
         • trail left behind when waving sparklers
         • movie frames being projected (seeing the frame 1 rather than the black of the shutter to give the appearance of a smooth-flowing film) 
         • a person viewing the film doesn't see the dark intervals between the images because the persistence of vision fills in the darkness by RETAINING the image of the previous frame 
       • Sperling
         • wondered HOW MUCH INFORMATION people can take in from briefly presented stimuli 
         • flashed an ARRAY OF LETTERS on the screen for 50ms 
         • participants had to report as many of the letters as possible 
         • indicated that immediately after a stimulus is presented, ALL or MOST of the stimulus is available for perception = "sensory memory" 
         • whole
           • participants were asked to report as many letters as possible from the WHOLE MATRIX 
           • average: 4.5/12 letters (37.5%)
         • partial
           • flashed matrix, then sounded one of the following cue tones to indicate WHICH ROW of letters the participants were to report 
           • average 3.3/4 letters (82%) 
           • concluded that in the WHOLE REPORT, participants saw 82% of letters but were not able to report all of these letters because they rapidly faded as the initial letters were being reported 
         • delayed partial
           • the presentation of cue tones was delayed for a fraction of a second after the letters disappeared 
           • participants could only slightly report more than 1 letter in a row (the equivalent of about 4 letters for all three rows - the same number of letters they reported using the whole report method)
       • iconic
         • VISUAL ICON 
         • brief sensory memory for VISUAL stimuli 
         • corresponds to the sensory memory stage in the Atkinson Shiffrin model 
         • visual info decays in less than 1 second 
       • echoic
         • sounds also persist in the mind 
         • persistence of SOUND
         • lasts for a few seconds after presentation of the original stimulus 
       • haptic
         • experiencing TOUCH briefly after removing hand 
     • short-term memory
       • holds 5-7 items for about 15-30 seconds 
       • control processes
         • active processes that can be CONTROLLED by the person
         • may differ from one task to another 
         • rehearsal
           • repeating a stimulus over and over in order to hold it in your mind 
         • memory strategies
           • strategies you might use to help make a stimulus more MEMORABLE 
           • example: relating digits in phone numbers to famous history dates 
         • attention strategies
           • help you FOCUS on information that is particularly important or interesting 
           • example: pneumonic devices 
         • encoding
           • the process of storing items into long-term memory 
           • retrieval
             • the process of remembering information that is stored in long-term memory 
     • long-term memory
       • hold a large amount of information for years or decades 
       • essential for storing information but before we can become AWARE of this stored info, it must be moved back into SHORT-TERM memory 

2. duration

   • decay
     • memory trace decays because of the PASSAGE OF TIME after sensing (hearing/seeing) a stimulus 
   • Brown-Peterson
     • 3-letter trigrams followed by a number 
     • varied the time between when they SAID the number and when the participant began RECALLING the LETTERS 
     • participants remembered 80% of letters after counting for 3 seconds BUT could remember an average of only 12% of the three-letter groups after counting for 18 seconds
     • participants forgot the letters because of DECAY
     • PREVENT rehearsal 
     • PI
       • PROACTIVE INTERFERENCE 
       • occurs when info that was learned previously INTERFERES with learning new information 
       • decrease in memory that occurs due to PRIOR learning 
       • example: when a previously used phone number has been recently changed 
       • if new number is SIMILAR to old number, then the memory of the old number will interfere with remembering the new number 
       • caused the decrease in memory observed in the later trials of Peterson/Peterson's experiment rather than DECAY 
       • thus, recalling EARLY letters in the list created interference that made it more difficult to remember the LATER letters in the list 
       • when rehearsal is PREVENTED: effective duration of SMT = 15-20 seconds 
       • release from PI
         • a situation in which conditions occur that ELIMINATE or REDUCE the decrease in performance caused by PI

3. capacity

   • items usually range from 4-9
   • George Miller 
   • digit span
     • the amount of digits a person can remember 
     • 7 items; plus or minus 2
   • chunking
     • posed by George Miller
     • describes the fact that small units can be combined into larger meaningful units (words -> phrases) 
     • CHUNK = collection of elementsthat are strongly associated with one another but are WEAKLY associated with elements in other chunks 
     • Ericsson et al. (1989) - trained average college student to have capacity of 79 digit span 

4. coding

   • refers to the way info is represented 
   • physiological
     • determining HOW a stimulus is represented by the FIRING of neurons 
   • mental
     • HOW the stimulus or an experience is REPRESENTED in the MIND
   • auditory
     • involves representing items in STM based on their SOUND 
     • Conrad (1964) 
     • letters that SOUND alike can be misinterpreted rather than letters that LOOK alike (example: F being misinterpreted by S or X, rather than E) 
     • remembering phone numbers by SOUND (repeating them) more often than visually 
   • visual
     • representing items visually 
     • remembering details of a floor plan or the layout of streets on a map 
     • Della Salla (1999) 
     • recalling patterns of filled in squares on a grid - cannot be coded VERBALLY 
     • could remember 9/30 squares 
   • semantic
     • representing items in terms of MEANING (measuring word meanings in order to remember actual words; i.e. professions like fireman and policeman)
     • Wickens et al. (1976) 
     • recalling words based on meaning, then being presented with words that have similar meanings (i.e. fruit); proactive interference occurred after being presented the first group of fruits (since participants were presented with more fruits after this, they would mix up the latter fruits with the former fruits as they all have the same meanings = fruits)
     • exposing participants to different groups (fruits + occupations + furniture, etc.) allowed for RELEASE from PI; release from PI depends on the words' CATEGORIES 

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