Coding, Capacity and Duration of Memory

Coding, Capacity and Duration of Memory

1. Research on Coding

   • When information gets into the memory system, it is stored differently depending on the memory store it's in.
     • ALAN BADDELEY (1966)
       • Baddeley gave four group different lists of words to remember:
         • Group 1: Acoustically Similar
         • Group 2: Acoustically Dissimilar
         • Group 3: Semantically Similar
         • Group 4: Semantically Dissimilar
         • Findings
           • When they needed to recall the list immediately after hearing it (STM), they tended to do worse with acoustically similar words
           • If participants were asked to recall a list after a time interval of 20 minutes (LTM), they tended to do worse on semantically similar words, this suggests that in long-term memory, information is coded by meaning in LTM.
       • EVALUATION
         • Artificial Stimuli
           • Word list had no personal meaning to the participants.
           • Not able to generalise the results to other memory tasks.
           • Limited application

2. Research on Capacity

   • Digit Span
     • JOSEPH JACOBS (1887)
       • - 4 digits given and asked to recall them in order out loud
       • - If correct the researcher reads out 5 digits and asks them again to recall out loud and so on until the participant can no longer recall the order correctly.
       • Findings
         • The mean span for digits was 9.3 items
         • The mean span for letters was 7.3
       • EVALUATION
         • Lacking validity
           • long time ago
             • lacked control due to confounding variables
               • participants may have been distracted
         • However, results of this study have been confirmed in other research, supporting its validity.
   • Span of Memory and Chunking
     • George Miller (1956)
       • Noted things come in sevens
         • E.g. Seven days a week, seven deadly sins, seven notes on musical scales
         • And so suggested that the capacity of STM was about 7 items (plus or minus two)
       • Chunking
         • Memory groups together sets of digits or letters into units or chunks
           • E.g. 546 784 987
       • EVALUATION
         • Not so many chunks
           • Cowan (2001) reviewed other research and estimated that the capacity of STM was only about 4 chunks

3. Research on Duration

   • Duration of STM
     • MARGARET AND LLOYD PETERSON (1959)
       • 24 participants - undergraduate students at a university
       • Took part in eight trials
         • In each trail they were given a consonant syllable (YCG) to remember and then given a 3-digit number to remember and count backwards from for a set amount of time. The different amount of times used were: 3,6, 9,12, 18. They were then asked to recall what the consonant syllable was.
           • Asking the participants to count backward prevented mental rehearsal of the consonant syllable.
           • The amount of time they were asked to count backwards was the retention interval.
       • Findings
         • The duration of short term memory is very short, and can be improved by verbal rehearsal
       • EVALUATION
         • Meaningless stimuli
           • Can't be generalised to real life memory activities
             • Lacked external validity
           • Not totally irrelevant as we do remember some meaningless information such as, mobile numbers.
   • Duration of LTM
     • HARRY BAHRICK AND CO. (1975)
       • 392 participants from American State, Ohio. Aged between 17-74.
         • High school yearbook used
           • Photo recognition
           • Free Recall
       • Findings
         • After 15 years of graduation, 90% accurate in photo recognition
           • After 48 years of graduation, accuracy fell to 70% in photo recognition
         • After 15 years of graduation, free recall was 60% accurate
           • After 48 years, accuracy fell to 30% for free recall
       • EVALUATION
         • Higher external validity
           • Used meaningful memories
           • Confounding variables were not controlled, as Bahrick's participants could have looked at the yearbook photos and rehearsed their memory over the years.