Coding, capacity and duration

Who studied coding

Baddeley 1966

Acoustically similar and dissimilar words

Cat, cab, can

Pit, few, cow

Semantically similar and dissimilar words

Great, large, big

Good, huge, hot

What did Baddeley find

STM is acoustic

Immediate recall with acoustically similar worse

LTM is semantic

Recall after 20 minutes with semantically similar worse

One strength of Baddeley

His study led to the development of the multi store model

One limitation of Baddeley

The words used have no personal meaning to participants

Tells us little about coding for everyday tasks

With more meaningful information people use semantic coding even for STM

Findings have limited application

Capacity Jacobs 1887 found

Participants could repeat 9.3 numbers and 7.3 letters

One strength of Jacob

Jacobs findings have been confirmed in controlled studies (Bopp and Verhaeghen)

Valid measure of STM digit span

Capacity Miller 1956 found

Span of STM is about 7 items plus or minus 2

One limitation of Miller

(Cowan) concluded capacity of STM is 4 plus or minus 1

Suggests Millers estimate of 5 items is more appropriate than 7

Chunking

Increases capacity

Gruping sets of digits or letters into meaningful units

who studied Duration of STM

Peterson and peterson 1959

Peterson and peterson found

(consonant syllables)

After 3 seconds average recall was about 80%

Ater 18 seconds about 3%

STM without rehearsal is up to 18 seconds

one limitation of Peterson and peterson

Recall of consonant syllables does not reflect meaningful everyday tasks

Lacks external validity

who studied LTM duration

Bahrick et al 1975

Bahrick et al found

(yearbook photos)

Recognition test - 90% after 15 years, 70% after 48 years

Free recall test - 60 % after 15 years, 30% after 48 years

One strength of Bahrick et al

Used meaningful memories

When studies used meaningless pictures recall was worse (Shepard)

Findings reflect a real estimate of the duration of LTM