Capacity, coding & duration Flashcards
What is the capacity of STM?
7+/- 2 items
What is the capacity of LTM?
Unlimited
What is the duration of STM?
18-30 secs
What is the duration of LTM?
Up to a lifetime
How is information coding in STM?
Mainly acoustically
How is information coding in LTM?
Semantically
How was the STM method of coding discovered?
- Baddeley gave ppts one of 4 lists of words - acoustically similar, acoustically dissimilar, semantically similar, or semantically dissimilar
- Ppts were tested on immediate recall and performed worst on acoustically similar words
= This shows that the information was being coded acoustically as interference occurred
How was the LTM method of coding discovered?
- Baddeley gave ppts one of 4 lists of words - acoustically similar, acoustically dissimilar, semantically similar, or semantically dissimilar
- Ppts were tested on delayed recall and performed worst on semantically similar words
= This shows that the information was being coded semantically as interference occurred
How was the capacity of STM discovered?
Jacobs’ digit test:
- Researcher reads out a 4 digit that the ppt must recall aloud
- Number of digits increases each time
- Experiment is stopped on the highest number of digits that can be recalled
MEAN DIGIT SPAN: 9.3
MEAN LETTER SPAN: 7.3
= STM capacity is 7+/-2 items
How has Baddeley’s coding research been criticised?
Artificial stimuli lacks mundane realism
No test on visual coding
How has Jacobs’ capacity research been criticised?
1887 = poor control - could have had confounding variables
How is Jacobs’ capacity research supported?
MILLER made similar observations of everyday life
How is Jacobs’ capacity research challenged?
COWAN reviewed other research and concluded that capacity was only 4/5 items
How was the duration of STM discovered?
Peterson & Peterson
- ppts were given a consonant syllable and a 3-digit number
- they counted back from the number until stopped, then had to recall the consonant syllable
- on each trial they stopped counting at a different time (3, 6, 9, 12 secs, etc)
RESULTS
after 3 secs - 80% accurate recall
after 18 secs - 10% accurate recall
= when rehearsal is prevented, STM duration is very limited
How was the duration of LTM discovered?
Bahrick
- 392 ppts aged 17-74
- tested on :
photo recognition of 50 photos, some from yearbook
free recall of graduate class
RESULTS
photo recognition - 90% accurate after 15 yrs, 70% after 48
free recall - 60% after 15 yrs, 30% after 48
= long duration + visual recall is most effective
