Coding, Capacity and Duration

  • Created by: Hclyne
  • Created on: 31-05-18 11:49

Research on Coding


Alan Baddeley (1966) gave different lists of words to four groups to remember:

  • Group 1; acoustically similar
  • Group 2; acoustically dissimilar
  • Group 3; semantically similar
  • Group 4; semantically dissimilar

P’s were shown the words and were asked to recall them in the correct order.
STM recall was worst with acoustically similar words.
LTM recall was worst with semantically similar words.


Artificial Stimuli: One limitation of Baddeleys study was that the words had no personal meaning to the participants. We should be cautious about generalising.
The findings from this study have limited application.

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Research on Capacity


Digit Span: Joseph Jacobs (1887) developed a technique to measure digit span.
Jacob’s found the mean span for digits was 9.3 items and 7.3 for letters.

Span of Memory and Chunking: George Miller (1956) noted that things come in sevens; (7 days of the week, 7 deadly sins etc...) suggesting that the capacity of STM is approx. 7 items (plus or minus 2). He also noted that people could remember 5 digits or letters through the use of chunking.


Lacking Validity: It was conducted a long time ago, results may not be valid due to confounding variables. Lacks temporal validity.

Not so Many Chunks: Miller may have overestimated the capacity of STM. Cowan (2001) reviewed research and concluded the capacity for STM was only 4 chunks.

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Research on Duration


Duration of STM: Peterson & Peterson (1959) gave P’s a consonant syllable as well as 3 digits to remember. The P’s were asked to count backwards from their number until told to stop.

Duration of LTM: Harry Bahrick (1975) studied recall using high school yearbooks using P’s aged 17-74. Recall was tested using photo recall and free recall.


Meaningless Stimuli in STM: Trying to memorise consonant syllables does not mimick real life. Lacking external validity.

Higher External Validiy: Bahrick studies real-life meaningful material - studies using meaningless material have found lower LTM recall.
However, confounding variables are not controlled.

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