CODING CAPACITY AND DURATION OF MEMORY

CODING CAPACITY AND DURATION OF MEMORY

1. RESEARCH ON CODING

   • Baddeley (1966) - four participant groups (acoustically similar/dissimilar, semantically similar/dissimilar). STM recall worse with acoustically similar and LTM recall worse with semantically similar.
     • Limited application because artificial stimuli used therefore had no meaning to stimuli so generalisations cant happen because some may code semantically for STM.

2. RESEARCH ON CAPACITY

   • DIGIT SPAN
     • Jacobs (1887) asked participants to recall digits in correct order until they no longer could. Mean span for digits was 9.3 items and letters was 9.3.
       • Limited as it was done very early, lacked control so results may not be valid. However, later research confirms results and supports Jacobs' study.
   • MEMORY SPAN AND CHUNKING
     • Miller (1956) - Most things comes in 7 so suggests capacity of STM is 7+-2 items. People can also recall 5 letters as well as 5 words by chunking sets of digits.
       • Cowan (2001) found that capacity of STM was 4 chunks - Miller overestimated.

3. RESEARCH ON DURATION

   • DURATION OF STM
     • Peterson and Peterson (1959) studied 24 undergraduate students and were given a trigram to remember whilst counting down. On each trial, it was found that the STM has a very short duration.
       • Stimuli was artificial and had no meaning to participants and does not reflect real life learning so it lacks external validity. But can explain how we learn meaningless things like phone numbers.
       • STM has limited capacity therefore memory will disappear if rehearsed due to spontaneous decay therefore this causes low internal validity.
   • DURATION OF LTM
     • Bahrick et al (1975) studied 392 participants aged 17 and 74. Participants were asked to recall people in HS yearbooks and a free recall test. Participants tested with 15 years were 90% accurate in photo recognition and this declined to 70% after 48 years. Free recall after 15 years was 60% accurate and then 30% accurate 48 years later.
       • Meaningful memories studied therefore higher external validity. Shepard (1967) studies with meaningless pictures on LTM recall were lowe. Confounding variables may not have been controlled as participants may have looked at yearbook photos.