Coding, Capacity and Duration of Memory

• Research on Coding (STM)


  Once information enters memory system it is stored in different formats, this is coding. Baddeley gave different lists of words to 4 groups of p's. G1: Acoustically Similar, G2: Acoustically Dissimilar, G3: Semantically Similar, G4: Semantically Dissimilar. P's were shown the original words and asked to recall them in correct order- immediately after hearing it (STM Recall) tended to do worse with acoustically sounding words as it conflicted with each other.
• Research on Coding (LTM)


  When p's were asked to recall the list 20 minutes later, p's did worse on semantically similar words due to words conflicting- suggesting that LTM is encoded semantically.
• Research on Capacity (Digit Span)


  Jacobs developed a technique to measure capacity, digit span where amount of numbers required to recall gradually increases. Found that the mean digit span across all p's was 9.3 items, and 7.3 letters.
• Research on Capacity (Chunking)


  Miller made observations of everyday practice- finding things come in 7s; suggesting that the span of STM is about 7+/-2 items.

  However, noted people can recall 5 words as well as 5 letters, by chunking. Meaning grouping sets of digits/letters into units.
• Research on Duration (STM)


  Peterson and Peterson tested 24 undergraduate students completing 8 trials, in each they were given a consonant trigram and a 3-digit number to countdown from (preventing any mental rehearsal). On each trial they had to count down for a different amount of time (a retention interval).

  Findings: without rehearsal, STM had a duration of 18 seconds.
• Research on Duration (LTM)

  Bahrick et al studied 392 p's from Ohio aged from 17-74. Their school yearbook was obtained and recall was tested in various ways: 1) photo recognition of 50 photos (some from their yearbook); 2) free recall test where they recalled names from their graduating class.

  P's who tested within 15 years of graduating were 90% accurate, after 48 years recall declined to 70%. Free recall was 60% within 15 years, and 30% after 48 years.
• AO3: Coding; Artificial Stimuli

  A limitation of Baddeley's study was that it wasn't done with meaningful material, word lists don't have any personal meaning to participants- meaning we should be cautious when making generalisations. E.g. when people are processing more personal information, they may use semantic coding even for short-term tasks. Findings then have limited application.
• AO3: Capacity; Lacking Validity

  A limitation of Jacob's study was that it was conducted a long time ago. Early psychological research lacked adequate control- some p's may have been distracted and not performed as well.

  Meaning the results aren't valid due to no confounding variables being controlled.

  Though, results of the study have been confirmed in later research- supporting its face validity.
• AO3: Capacity; Too many chunks

  A limitation of Miller's research is that he may have overestimated the capacity of STM. For example, Cowan reviewed other research and concluded that the capacity of STM was only 4 chunks- implying the lower end of Miller's estimate is more appropriate.
• AO3: Duration; Meaningless Stimuli in STM Study

  A limitation of Peterson and Peterson's study is that stimuli was artificial- memorising consonant trigrams isn't reflective of real-life memory activities. It lacks ecological or external validity. But may be applied to more meaningless scenarios like remembering phone numbers.
• AO3: Duration; Strength of Stimuli

  A strength of Bahrick's study is it's high external validity; stimuli used was meaningful.

  Though the downside of this is confounding variables were not controlled; some p's may have looked over their yearbooks and hence rehearsed.