Psychology: Memory - Coding, capacity and duration of memory

Coding - Baddeley (1966) Acoustic and semantic procedure

Acoustically similar words e.g. cat, cab

Semantically similar words e.g. great, big

Coding - Baddeley (1996) Acoustic and semantics findings

Immediate recall worse with acoustically similar words, STM is acoustic

Recall after 20 mins worse w/ semantically similar words, LTM is semantic.

Capacity - Jacobs (1887) Testing digit span procedure

Researcher reads four digits and increases until the pps can’t recall order correctly.

Final number = digit span

Capacity - Jacobs (1887) Testing digit span findings

Pps could repeat back 9.3 numbers and 7.3 letters in the correct order immediately after

Capacity - Miller (1956) Magic number 7 ± 2 procedure

Observed that everyday things come in seven e.g. seven day of week, seven deadly sins

Capacity - Miller (1956) Magic number 7 ± 2 findings

Span of STM is 7 ± 2 but is increased by chunking - grouping sets into meaningful units

Duration STM - Peterson and Peterson (1959) Consonant syllables procedure

24 students given consonant syllables to recall (YCG) and 3-digit number to count backwards.

Retention interval varied: 3,6,9,12 secs

Duration STM - Peterson and Peterson (1959) Consonant syllables findings

After 3 secs average recall 80%

After 18 secs average recall 3%

STM duration w/o rehersal is up to 18 secs

Duration LTM - Bahrick et al. (1975) Yearbook photos procedure

392 American pps aged 17-74

1. Recognition test - 50 photos from high school yearbooks

2. Free recall test - pps listed names of graduating class

Duration LTM - Bahrick et al. (1975) Yearbook photos findings

Recognition test - 90% accurate after 15 yrs, 70% after 48yrs

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

Strength - Baddeley’s study

• Identified two memory stores

• Later research shows there is exceptions to Baddeley’s findings

• But STM is mostly acoustic and LTM is mostly semantic

• Led to development of multi-store model

Limitation - Baddeley's study

• Used artificial stimuli

• Words had no personal meaning so tells us little about coding for everday tasks

• When processing more meaningful info, ppl use semantic coding even for STM

• Finding of study has little application

Strength - Jacobs’ study

• Has been replicated

• Old study which may have lacked adequate controls

• But Jacobs’ findings confirmed in later controlled studies

• Shows study is valid measure of STM digit span

Limitation - Miller’s study

• Overestimates STM capacity

• Cowan (2001) reviewed other research

• Concluded that capacity was 4 chunks

• Suggest Millers estimate of 7 is less appropriate

Limitation - Peterson and Peterson study

• Meaningless stimuli

• Sometimes try to recall meaningless things so the study is not completely irrelevant

• Recall of syllables isn't meaningful

• Lacks external validity

Strength - Bahricks study

• High external validity

• Meaningful memories studies

• When study was done w meaningless pics recal rates lower

• Bahricks findings reflect a more ‘real’ estimate of duration of LTM