Coding, Capacity and Duration of Memory

Coding, Capacity and Duration of Memory

1. CODING

   • Alan Baddeley (1966)
   • Group One: acoustically similar. Group Two: acoustically dissimilar. Group Three: semantically similar. Group Four: semantically dissimilar
   • recall task immediately STM recall - did worse on acoustically similar words
   • recall task 20 mins later LTM recall - did worse with semantically similar words

2. CAPACITY

   • Joseph Jacobs (1887)
     • the researcher gives 4 digits and then participant is asked to recall them in correct order. This determines persons individual span
     • conducted long time ago - lacked adequate control (participants distracted) so don's perform as well results not valid - confounding variables not controlled
   • George Miller (1956)
     • Span of STM is about 7 items also recall 5 words as well as they can recall 5 letter - through method known as chunking
       • Cowan (2001) reviewed other research and concluded that STM capacity is only 4 chunks

3. Duration

   • Peterson and Peterson (1959)
     • tested 24 undergraduate - eight trials each given participant syllable and 3 digit number. Told to count backward from 3 digit number (prevent mental rehearsing) In each trial they were told to stop after different amount of time: retention interval. STM has short duration unless rehearsed
     • Artificial stimuli does not reflect real life memory activities. Lack External Validity. However we sometimes learn meaningless things: number - task not completely irrelevant
   • Harry Bahrick et al (1975) studied 392 participants from America Ohio aged 17 and 74. High school yearbooks obtained from participants or school. Recall tested in 1) photo recognition: test consisting of 50 photos. 2) free recall test where participant recall names of graduating class
     • photo recognition: 15 years - 90% accurate. 48 years - 70% accurate
     • free recall: 15 years - 60% accurate. 48 years - 30% accurate
   • high external validity - real life meaningful memories studies. However confounding variables not controlled such as participants may have looked at year book and rehearsed