2.1 coding, capacity and duration đź’š

Key terms

STM - the limited-capacity memory store. Coding is mainly acoustic, capacity is between 5 and 9 items and duration is about 18 seconds

LTM - the permanent memory store. Coding is mainly semantic. It has unlimited capacity and duration is up to a lifetime

Coding - the format in which information is stored

Capacity - the amount of information that can be held in a memory store

Duration - the length of time information can be held in memory

Research on coding

Baddeley

  • Gave lists of words for 4 groups to remember: acoustically similar, acoustically dissimilar, semantically similar, semantically dissimilar

  • found when participants recalled from STM (immediately), they did worse with acoustically similar words

  • When participants recalled from LTM (after 20 mins), they did worse with semantically similar words

Evaluation

  • Identifies a clear difference between memory stores which led to the multi-store model

  • Artificial stimuli. The semantic material had no personal meaning to the participants

Research on capacity

Jacob’s - digit span

  • the researcher reads out digits, the digits continue to increase until incorrect

  • The mean for digits was 9.3. The mean for letters was 7.3 (STM)

Miller

  • noted everything comes in 7s. Suggests capacity of STM is 7 (+-2)

  • Also people can recall 5 words as easily as 5 letters by chunking

Evaluation

  • Jacob’s study has been replicated, showing it’s reliable. And counting removes confounding variables so its valid

  • Miller overestimated STM capacity. Cowan found capacity is 4 (+-1)

Research on duration

STM - Peterson

  • gave participant a consonant syllable to remember, then given a 3 digit number to count down from to prevent mental rehearsal

  • Told to stop at varying times. After 18 seconds, recall was 3%

LTM - bahrick

  • assessed memory of high school graduates using their high school yearbooks. Done through photo recognition

  • Within 15 years of graduation recall was 90% accurate

  • After 48 years, recall was 70% accurate

  • This decreased for both in the free recall test

Evaluation

  • Peterson used artificial stimulus, lacks external validity as we rarely remember meaningless information

  • High external validity, Bahrick used meaningful memories and found recall rates were lower when meaningless pictures were used (Shepard)