Coding, capacity and duration of memory - AO1 Flashcards
How is STM coded?
Acoustically
What is the capacity of STM?
Miller suggested this is small - 7+-2 items
- This can be improved by chunking, making small sets/groups of items
- This reduces the number of items overall
What is the duration of STM?
Short, 18-30 seconds
However it can be extended by rehearsal loop
How is LTM coded?
Semantically
What is the capacity of LTM?
No limit has been found
Information can be lost but not because the LTM is full. The information may still be in LTM but not accessible
What is the duration of LTM?
Potentially unlimited as recall of childhood events is normal even for the oldest people
What is research on coding?
Baddeley (1966): Gave different lists of words to four groups of PPs to remember.
Group 1: Acoustically similar
Group 2: Acoustically dissimilar
Group 3: Semantically similar
Group 4: Semantically dissimilar
* When asked to recall words immediately, recalling from STM, PPs tended to do worse with acoustically similar words
* When asked to recall words 20 minnutes later, recalling from LTM, they did worse with semantically similar words
What are two researches on capacity?
Jacobs (1887): Found out by measuring digit span
Researcher reads out four digits and PP recalls this out loud in the correct order
If this is correct researcher reads out five digits and so on unitl the PP cannot recall the order correctly
- This indicates the individual’s digit span
- Jacob found the mean digit span for all PPs was 9.3 items and letters were 7.3
Miller (1956): Made observations of everyday practice
Noted that many things come in sevens, days of the week, deadly sins - Thought that the digit span of STM is 7±2 items
- People can recall five words ass much as they can recall five letters
- This is due to chunking - grouping sets of digits or letters into units or chunks
What is research on the duration of STM?
Peterson and Peterson (1959): Tested 24 students in eight trials each
On each trial the student was given a consonant syllable to rememeber, they were also given a three digit number
The student counted backwards from this number until told to stop
The counting backwards was to prevent mental rehearsal
On each trial they were told to stop after varying periods of time: 3, 6, 9, 12, 15 or 18
- After three seconds average recall was about 80%
- After 18 seconds it was about 3%
- STM duration may be 18 seconds unlesswe repeat them over and over
What is research on the duration of LTM?
Bahrick et al. (1975): Studied 392 American PPs aged 17 to 74.
High school yearbooks were obtained from PPs or directly from school
(1) Photo recognition test consisting of 50 photos, some from PPs yearbooks
(2) Free recall test where PPs recalled names of their graduating class
- PPs tested withing 15 years of graduation were about 90% accurate in photo recognition
- After 48 years, recall declined to about 70% for photo recognition
- Free recall was less accurate than recognition
- About 60% after 15 years, dropping to 30% after 48 years
- Shows LTM may last up to a lifetime for some material
