CODING, CAPACITY AND DURATION OF MEMORY

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  • Coding and Capacity and Duration of Memory
    • Research on coding= coding the format in which information is stored in the various memory stores.
      • Alan Baddeley (1966) gave different lists of words to four groups of participants to remember:
        • Group 1: (acoustically similar): words sounded similar (e.g. cat, cab, can).
          • Participants were shown the orginal words and asked to recall them in the correct order. When they had to this recall task immediately after hearing it (STM recall), they tended to do worse with acoustically similar words. If participants were asked to recall the word list after a time interval of 20 minutes (LTM recall), they did worse with the semantically similar words.This suggests that information is coded semantically in LTM.
            • Evaluation: Artificial stimuli rather than meaningful material. The word lists had no personal meaning this means we should be cautious about generalizing the findings to different kinds of memory tasks. For example, when processing more meaningful information, people may use semantic coding even for STM . Suggests that the findings from this study have limited application.
        • Group 2:(acoustically dissimilar): words sounded different (e.g. pit, few, cow)
        • Group 3: (semantically similar): words with similar meanings (great, large, big)
        • Group 4:(semantically dissimilar): words that all had different meanings (e.g. good, huge, hot)
    • Research on capacity= The amount of information that can be held in a memory store.
      • Digit Span-Joseph Jacobs (1887) developed digit span. Researcher gives for example 4 digits and the participant has to recall the 4 digits in the correct order out loud. If they are correct, the research reads out 5 and so forth until the participant can no longer recall the order correctly. Jacob found the mean span for digits was 9.3 and 7.3 for letters.
        • Evaluation: Lacking validity as it was conducted a long time ago. Early research often lacked adequate control. Confounding variables may have not been controlled creating invalid results. Some participants may have been distracted so dint perform as well. However, other research has proved this research to be valid.
      • Span of Memory and Chunking-George Miller (1956) made observations of everyday practice. 7+/-2 items. However, Miller also noted people can recall 5 words as well as they can recall 5  letters. They do this by chunking- grouping sets of digits or letters into units or chunks.
        • Evaluation: One limitation of Millers research is that he may have over estimated the capacity of STM, for example Cowan 2011 reviwed other researchand conlcuded the STM was only 4 chunks. This suggests Milers lower end estimate (5) is more appropriate than (7) items.
      • Research on duration=The length of time information can be held in memory.
        • Duration of STM-Margaret and Lloyd Peterson 1959 tested 24 undergraduates. Each student took part in 8 trials. On each trail the student was a given a consonant syllable to remmeber and was also given a 3 digit number. The student was then asked to count backwards from that 3 digit number to prevent mental rehearsal of consonant syllable.On each trial they were told to stop after a different amount of time -3,6,9,12,15 or 18 seconds this is called the retention interval.It showed STM has a very short duration unless we have verbal rehearsal.
          • Evaluation: Stimulus material was artificial, lacked external validity as memorizing consonant syllables does not reflect real life memory activities e.g. meaningful information. Not irrelevant as we try to remember phone numbers,
          • Duration of STM-Limited capacity. 7+/-2 items. Mainly acoustic coding. Duration 18-30 seconds.
        • Duration of LTM- Bahrick and colleagues (1975) studied 392 participants from the American state of Ohio ages between 17-74. High school year books were attained. Recall was tested in two ways-1) Photo-recognition test coniststing of 50 photos, some from the participants yearbook;2) free recall test where participants recalled all the names of their graduating class. Tested within 15 years 90% accurate, after 48 years 70% photo recognition. Free recall- after 15 years 60% accurate and dropped to 30% after 48 years. LTM can last a very time long time indeed
          • Evaluation: High external validity as real-life meaninigful memories were used. Meaningless pictures recall was lower in other studies e.g. Shepard 1967. However, confounding variables are not controlled such as some participants may have looked at their yearbook photos and rehearsed.
          • Duration of LTM- Permanent memory store. Coding is mainly semantic (meaning) and has unlimited capacity.

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