Short and Long-Term Memory

  • Capacity, duration and coding of STM and LTM 
  • Evaluation of capacity, duration and coding of STM and LTM
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  • Created by: clareh8
  • Created on: 19-12-21 19:29

Short-Term Memory

Capacity:

  • 7+/-2 (the magic number )
  • Joseph Jacobs (1887) developed a technique to measure digit span using this technique he discovered the magic number 
  • George Miller (1956) wrote an article called the magic number seven plus or minus two, in which he reviewed psychological research and concluded that the span is about 7 digits. 

Duration:

  • less than 18 seconds
  • Lloyd and Margaret Peterson (1959) discovered the duration of STM

Coding

  • Encoded acoustically
  • Alan Baddeley (1966a/1966b) discovered the coding of STM
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Long-Term Memory

Capacity:

  • Unlimited

Duration:

  • unlimited (2 minutes - 100 years) 
  • Harry Bahrick et al. (1975) used 400 previous students and did a photo-recognition test using a yearbook 

Coding

  • Encoded semantically 
  • Alan Baddeley (1966a/1966b) discovered the coding of LTM by using word lists 
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Evaluation - Capacity

All evalutation/discussion points are written in a PEE paragraph  (green - strength, blue - discussion, red - criticism)

The size of the chunk affects how many chunks you can remember. Simon (1974) found that people had a shorter memory span for larger chunks, such as 8 word phrases, than smaller chunks, such as one-syllable words. This continues to support the view that STM has a limited capacity and refines our understanding. 

The capacity of STM is not the same for everyone. Jacobs also found that recall (digit span) increased steadily with age; eight year olds could remember an average of 6.6 digits whereas the mean for 19 year olds was 8.6 digits. This age increase might be due to changes in the brain capacity, and/or to the development of strategies such as chunking. This suggests that the capacity of STM is not fixed and individual differences may play a role. 

One limitation of Miller's research is that he may have overestimated the capacity of STM. For example, Cowan (2001) reviewed other research and concluded that the capacity for STM was only about four chunks. This suggests that the lower end of Miller's estimate (five items) is more appropiate than seven items. 

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Evaluation - Duration

All evalutation/discussion points are written in a PEE paragraph  (green - strength, blue - discussion, red - criticism)

One strength of Bahricks' et al.s study is that it has a higher external validity. Real-life menaingful memories were studied. When studies on LTM have been conducted with meaningless pictures to be remembered, recall rates were lower. 

Another criticism of research investigating STM is that it is artificial. Trying to memorise constant syllables does not truly reflect most everyday memory activites where what we are trying to remember is meaningful. However, we do sometimes try to remember fairly meaningless things, such as groups of numbers (phone numbers). This means that, although the task was artificial, the study does have some relevance to everyday life. 

A criticism of the Petersons' study is that it did not actually measure what it set out to measure. In the Petersons' study participants were counting the numbers in their STM and this may displace or 'overwrite' the syllables to be remembered. Reitman (1974) conducted research which suggested that the forgetting in the Petersons' study was due to displacement rather than decay. 

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Evaluation - Coding

All evalutation/discussion points are written in a PEE paragraph  (green - strength, blue - discussion, red - criticism)

Baddeleys' methodology has been criticised. In the study by Baddeley, STM was tested by asking participants to recall a word list immediately after hearing it. LTM was tested by waiting 20 minutes. It is questionable as to whether this is really testing LTM. This casts doubt on the validity of Baddeley's research because he wasn't testing LTM after all. 

Frost (1972) and Nelson & Rothbart (1972) conducted research that suggested LTM ay not be exclusively semantic. Brandimote et al. (1992) also conducted research which suggested that STM may not be exclusively acoustic 

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