Memory
Coding, capacity and duration of memory
Research on coding
Coding: converting information between different forms
Alan Baddeley (1966) – four categories:
Acoustically similar
Acoustically dissimilar
Semantically similar
Semantically dissimilar
Method
1. Shown the words and asked to recall them in the correct order
Findings
When they recalled immediately – recalled from STM – tended to do worse
with acoustically similar words.
When they recalled after 20 minutes – recalled from LTM – tended to do
worse with semantically similar words.
Conclusion
STM codes acoustically
LTM codes semantically
Evaluation
Separate memory stores
o Has stood the test of time
o Important in understanding
o Led to MSM
o Counterpoint: later research showed exceptions to Baddeley’s
findings
Controlled lab setting and replicated
o Findings replicated on numerous occasions
o Distinction between STM and LTM and coding is widely
accepted
o Face validity e.g. revision
o Valuable as it has advanced out understanding of memory and
contributed to memory models
, - Artificial stimuli – lacked mundane realism
o Not meaningful or personal material – learning lists of words
o May not be generalisable to everyday life
o Semantic coding may be used even for STM tasks in real life as
it is meaningful information
o Left for 20 minutes before testing LTM – too soon in comparison
to real life
o Limited application and cannot be generalised
o Lacks ecological validity
Research on capacity
Digit Span (how many numbers recalled) – Joseph Jacobs (1887)
Method
1. Researcher reads out 4 digits and the participant recalls these out
loud in the correct order.
2. If correct, the research reads out 5 digits etc, until the participant
recalls incorrectly.
Sequences should have no meaning, no repetition and not be acoustically
similar.
Findings
Mean span for digits across all participants was 9-3.
Mean span for letters was 7-3.
Span of memory and chunking – George Miller (1956)
Method
1. Made observations of everyday practice
Findings
Things come in sevens: notes on the musical scale, days of the week,
deadly sins.
Conclusions
Span of STM is about 7 +/- 2 items
People can recall 5 words as easily as 5 letters: chunking
Chunking – grouping sets of digits or letters in units or chunks
Evaluation
Jacobs has been replicated
, o Early research often lacked adequate control e.g. distraction
during testing meant digit spans might have been
underestimated (confounding variable)
o May make findings invalid
o Findings confirmed by other, better controlled studies since
o Bopp and Verhaeghen 2 005
o Therefore, it is valid
Real-world application
o Face validity
o E.g. postcodes, number plates
o Helped develop theories e.g. MSM
o Often naturally try to have information not exceeding 7 chunks
– valid and useful in an everyday context
- Not as many chunks
o Miller may have overestimated STM capacity
o Nelson Cowan (2004) reviewed other research and concluded
the capacity of STM is only 4 +/- 1 chunks
o Suggests Miller’s lower estimate of 5 is more appropriate than 7
Research on duration
Duration of STM – Margaret and Lloyd Peterson (1959)
Method
1. Tested 24 students in 8 trials each
2. Each trial: student given a consonant syllable to remember and a 3-
digit number to count backwards from until told to stop
Counting back – prevented mental rehearsal of the syllable
3. Time until told to stop: 3, 6, 9, 12, 15 or 18 seconds (the retention
interval)
Findings
After 3 seconds: average recall was about 80%
After 18 seconds: average recall was about 3%
Conclusion
o Suggest that STM duration may be about 18 seconds without
rehearsal
Duration of LTM – Harry Bahrick et al. (1975)
Method
1. Studied 392 American participants aged 17-74
Coding, capacity and duration of memory
Research on coding
Coding: converting information between different forms
Alan Baddeley (1966) – four categories:
Acoustically similar
Acoustically dissimilar
Semantically similar
Semantically dissimilar
Method
1. Shown the words and asked to recall them in the correct order
Findings
When they recalled immediately – recalled from STM – tended to do worse
with acoustically similar words.
When they recalled after 20 minutes – recalled from LTM – tended to do
worse with semantically similar words.
Conclusion
STM codes acoustically
LTM codes semantically
Evaluation
Separate memory stores
o Has stood the test of time
o Important in understanding
o Led to MSM
o Counterpoint: later research showed exceptions to Baddeley’s
findings
Controlled lab setting and replicated
o Findings replicated on numerous occasions
o Distinction between STM and LTM and coding is widely
accepted
o Face validity e.g. revision
o Valuable as it has advanced out understanding of memory and
contributed to memory models
, - Artificial stimuli – lacked mundane realism
o Not meaningful or personal material – learning lists of words
o May not be generalisable to everyday life
o Semantic coding may be used even for STM tasks in real life as
it is meaningful information
o Left for 20 minutes before testing LTM – too soon in comparison
to real life
o Limited application and cannot be generalised
o Lacks ecological validity
Research on capacity
Digit Span (how many numbers recalled) – Joseph Jacobs (1887)
Method
1. Researcher reads out 4 digits and the participant recalls these out
loud in the correct order.
2. If correct, the research reads out 5 digits etc, until the participant
recalls incorrectly.
Sequences should have no meaning, no repetition and not be acoustically
similar.
Findings
Mean span for digits across all participants was 9-3.
Mean span for letters was 7-3.
Span of memory and chunking – George Miller (1956)
Method
1. Made observations of everyday practice
Findings
Things come in sevens: notes on the musical scale, days of the week,
deadly sins.
Conclusions
Span of STM is about 7 +/- 2 items
People can recall 5 words as easily as 5 letters: chunking
Chunking – grouping sets of digits or letters in units or chunks
Evaluation
Jacobs has been replicated
, o Early research often lacked adequate control e.g. distraction
during testing meant digit spans might have been
underestimated (confounding variable)
o May make findings invalid
o Findings confirmed by other, better controlled studies since
o Bopp and Verhaeghen 2 005
o Therefore, it is valid
Real-world application
o Face validity
o E.g. postcodes, number plates
o Helped develop theories e.g. MSM
o Often naturally try to have information not exceeding 7 chunks
– valid and useful in an everyday context
- Not as many chunks
o Miller may have overestimated STM capacity
o Nelson Cowan (2004) reviewed other research and concluded
the capacity of STM is only 4 +/- 1 chunks
o Suggests Miller’s lower estimate of 5 is more appropriate than 7
Research on duration
Duration of STM – Margaret and Lloyd Peterson (1959)
Method
1. Tested 24 students in 8 trials each
2. Each trial: student given a consonant syllable to remember and a 3-
digit number to count backwards from until told to stop
Counting back – prevented mental rehearsal of the syllable
3. Time until told to stop: 3, 6, 9, 12, 15 or 18 seconds (the retention
interval)
Findings
After 3 seconds: average recall was about 80%
After 18 seconds: average recall was about 3%
Conclusion
o Suggest that STM duration may be about 18 seconds without
rehearsal
Duration of LTM – Harry Bahrick et al. (1975)
Method
1. Studied 392 American participants aged 17-74
