Short & Long-term memory

Short & Long-term memory

1. Capacity, Duration & Coding Part 1

   • capacity
     • measure of how much can be held in memory
   • Duration
     • how long a memory lasts before it is no longer available
   • Coding
     • way in which info is changed so that it can be stored in memory

2. Capacity, Duration & Coding Part 2

   • STM
     • Capacity
       • can be assessed using a digit span test
       • Miller (1956)
         • 7 +/- 2 chunks of information
     • Duration
       • Peterson & Peterson (1959)
         • less than 18 seconds
     • Coding
       • Baddeley (1966a &1966b)
         • coded in acoustic format
   • LTM
     • Capacity & Duration
       • supposedly unlimited capacity that can last a lifetime
       • Bahrick et al (1979)
         • participants could remember names of former classmates with 90% accuracy 15 years after graduation
         • declined to 70% after 48 years
     • Coding
       • Baddeley (1966a & 1966b)
         • Semantically

3. Evaluation

   • Capacity of STM may be more limited
     • Cowan (2001) reviewed a variety of sttudies on capacity of STM -l likely to be limited to about four chunks rather than 7 +/- 2
     • contradicts Miller (1959)
     • matters as original findings have not been replicated by subsequent studies & sugest STM capacity is more limited than originally thought
   • testing methods - artificial
     • memorising strings of digits/consonants does not reflect memory in real life
     • although sometimes we do try and remember meaningless things e.g. phone no.s/postcode
     • matters as studies may lack ecological validity, but research may be useful for understanding memory for certain types of info
   • memory improves with age
     • Jacobs (1887) recall increased steadily with age; 8yrs could remember 6.6 digits, 19yrs 8.6 digits
     • may be due to increase in brain capacity or people develop strategies to improve memory as get older
     • suggests capacity is not 7 +/- 2 & individual differences play a role in differences found
   • STM - May not just be acoustic
     • Brandimote et al (1992) participants used visual coding in STM when given visual take & prevented from verbally rehearsing
     • usually translate visual images into verbal codes in STM but these participants were prevented from doing this - used visual codes
     • suggests may be multiple types of coding in STM & is not exclusively acoustic
   • LTM - not just semantic
     • Frost (1972) LT recall related to visual & semantic categories
     • Rothbart (1972) found evidence for acoustic coding in LTM
     • LT might be encoded using acoustic, visual & semantic info, depending on type of info being remembered