Research on Features of Memory

What is Capacity

the amount you can remember

Studies into STM Capacity

Jacobs and Miller

Overview of Jacobs Research

• digit span test

• participants are read sequence of letters/numbers

• asked to repeat sequence immediately

• additional digit added each trial

• until participant can’t recall correctly

Findings of Jacobs Research

• digits = 9

• letters = 7

• less digits to remember than letters

Overview of Millers Research

• review of research into capacity

• based off Millers observation

• 7 relevance in real life

• e.g. deadly sins, days of the week, musical scale

Findings of Millers Research

• 5-9 items

• 7(±/- 2) items

Capacity of STM

7 (±/- 2) items (Miller)

Capacity of LTM

infinite

Research Support strength of Capacity Research

• digit span increases with age

• 8yo = 6.6 digits average

• 19yo = 8.6 digits average

• confirms Jacobs 5-9 items so high validity

Research Against criticism of Capacity Research

• STM limited to 4 chunk items

• Cowan review variety of studies in 2001 (not 20th CE)

• low reliability since others suggest capacity smaller than 5-9

• study not reliable measurement of capacity

What is Coding

the way memories are stored

Coding of STM

acoustic (Baddeley)

Coding of LTM

semantic (Baddeley)

Studies into Coding

Baddeley

Overview of Baddeleys Research

• 4 groups given different lists of words to remember

• acoustically similar (sound)

• acoustically dissimilar (sound)

• semantically similar (meaning)

• semantically dissimilar (meaning)

• asked to recall word lists immediately

• asked to recall word lists 20 minutes later

Results of Baddeleys Research

• immediate recall = struggle acoustically similar

• suggests information coded acoustically in STM

• 20 minute recall = struggle semantically similar

• suggests information coded semantically in LTM

Reliability criticism of Baddeleys Research

• findings not replicable

• participants given visual task and prevented verbal rehearsal they used visual coding in STM

• STM isn’t coded exclusively acoustically - dependent on task

• future research use wide variety of tasks to develop understanding of coding

Mundane Realism criticism of Baddeleys Research

• stimuli used are artificial and no personal meaning

• not telling of everyday life memory usage (meaningful)

• maybe with meaningful coded in semantic

• future research use meaningful material develop understanding different memory stores

What is Duration

the length of time the memory is stored for

Duration of STM

18s (Peterson and Peterson)

Duration of LTM

lifetime (Bahrick et al)

Studies into STM Duration

Peterson & Peterson

Overview of Peterson and Petersons Research

• 24 undergrad students in 8 trials

• trigram (ABC) and 3 digit number (123)

• students count backwards out loud from 3 digit number

• to prevent mental rehearsal of trigram

• told to stop at different time

• 3, 6, 9, 12, 15, 18 seconds

• retention interval

• asked to recall trigram

Result of Peterson and Peterson Research

• participants correctly recall trigram

• 80% after 3s

• 3% after 18s

Conclusion of Peterson and Petersons Research

STM has short duration of 18s

Mundane Realism criticism of Peterson and Petersons Research

• trigram to remember and recall

• trigram is meaningless to participant

• no relevance to everyday memory task

• not use to conclude duration of STM

Not Measured criticism of Peterson and Peterson Research

• not measured what it set out to measure (STM duration)

• task consisted of remembering trigram with distraction to prevent mental rehearsal

• more likely to forget trigram due to interference

• low validity not use to conclude duration

Studies into LTM Duration

Bahrick et al

Overview of Bahrick et als Research

• 392 US 17-74

• 1 group photo recognise photos from highschool

• 1 group free recall list names without prompts

Results of Bahrick et als Research

• within 15 years

• 90% accurate photo

• 60% accurate free recall

• after 48 years

• 70% accurate photo

• 30% accurate free recall

Conclusion of Bahrick et als Research

LTM has very long duration of up to lifetime

Sample strength of Bahrick et als Research

• large sample

• high generalisability

• reflect wider population

• increase population validity

Situational criticism of Bahrick et als Research

• doesn’t account for situation

• e.g missed school or if social

• reduce external validity