Encoding in Short-term and Long-term memory.

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                          Cognitive Psychology: Human Memory

Encoding in Short-term and Long-term memory


  • 1960’s- Controversy concerning the nature of coding in memory.

        - Baddeley tested if acoustic coding (based on the sound of the word) is used in STM.

        -Semantic coding (based on the memory of the word) us used in LTM.

  • Research based on Conrad’s research- 1964

- Argued STM encodes information acoustically

-No clarification which code preferred by LTM

  • Baddeley- aimed to confirm Conrad’s findings and establish understanding of LTM

Procedure:- Laboratory experiment using independent measures design

        - 4 types of word list –first 2-experimental conditions

        -Other 2 – control conditions

  • Acoustically similar (e.g. meet/feet/sweet)
  • Semantically similar (e.g. neat/clean/tidy)
  • Acoustically dissimilar (e.g. hot/far/jam)
  • Semantically dissimilar (e.g. pen/jump/day)

  • Independent variable- type of word list (acoustically similar/dissimilar or semantically similar/dissimilar)
  • Dependent variable- number of substitution errors made (one item confused with another)- Indicates main form on encoding 
  • Participants recalled common words readily-similar frequency words
  • Participants asked to recall words in same order of presentation immediately for STM/ after timed delay =LTM


  • STM (immediate recall)- more substitution errors on acoustically similar lists than acoustically dissimilar.

Conrad (1964)- confirms notion that acoustic coding used in STM.

  • No difference in performance at immediate recall between semantically similar and semantically dissimilar –Meaning not important in STM
  • LTM (delayed recall)-no difference in performance between acoustically similar and acoustically dissimilar lists- acoustic coding not used in LTM.
  • Semantically similar words confusing than semantically dissimilar lists-Important for LTM coding
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Conclusions –findings suggest nature of encoding is different in STM and LTM.

  • STM- is acoustic not semantic

        - Encoding is on the basis of sound not meaning

        - We rehearse/say over words in STM.

  • LTM- coding is semantic, not acoustic

        -Encoding based on meaning of word not sound.


  • Study lacks mundane realism – people in real life do not learn word lists under controlled conditions- experiment lacks ecological validity, not generalise to everyday memory.      
  • Not all information in LTM is in semantic form –words are presented visually ...

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