Features of Memory

• Capacity


  The amount of information that can be held in a memory store
• Capacity of short term memory study

  Jacobs 1887 - The researcher read aloud an increasing number of digits and participants had to recall in the correct order until they could no longer recall correctly. This tells you the individuals digit span. The mean digit span of numbers was 9.3 and the mean digit span of letters is 7.3
• chunking


  Grouping sets of information into units / chunks
• Chunking and short term capacity / span study

  Miller 1956 - Everyday practices come in sevens. So the span of short term memory is 7 ± 2 , however people can recall 5 numbers as easy as 5 letters.
• duration


  the length of time information is held in a memory store
• Duration of short term memory study

  Peterson and Peterson (1959) - Tested 24 students with 8 trials each, given a consonant syllable to remember and a three digit number. The students had to count back from the number (to prevent mental rehearsal) until they were told to stop at either 3, 6, 9, 12, 15, or 18 seconds (the retention interval). After 3 seconds recall was 80%. After 18 seconds recall was 3%. So short term memory duration is 18 seconds without rehearsal
• Duration of long term memory study

  Bahrick 1975 - 392 American participants age 17 - 74 and their school yearbooks. They were tested on recognition of 50 photos and free recall of all the people in their graduating class. Participants who had graduated 15 years ago (or less) recalled 90% of photos and 60% of names, those who graduated over 48 years ago only recalled 70% of photos and 30% of names. So long term memory can last a long time.
• Coding


  the format in which information is stored in the various memory stores
• Coding in short term and long term memory study

  Baddeley 1966 - each group received a different list of words

  G1 - acoustically similar

  G2 - acoustically dissimilar

  G3 - semantically similar

  G4 - Semantically dissimilar

  Participants were shown the words immediately after and then 20 minutes later and asked to recall them in the correct order
• Coding in short term memory and long term memory study findings

  Baddeley - 1966

  Immediately after ( short term memory) acoustically similar words were recalled the worst.

  After 20 minutes ( long term memory) semantically similar words were recalled the worst.

  So short term memory is coded acoustically and long term memory is coded semantically
• Evaluation of coding study

  + Clear difference between short and long term stores - Helped design multi store model

  x Artificial stimuli - word lists have no emotional or extreme meaning so coding may vary in different memory tasks
• evaluation of capacity studies

  + validity of Jacobs 1887 - it was replicated by Bopp and Verhaegen 2005. Most older studies lack adequate controls and have confounding variables

  x Miller 1956 overestimated short term memory capacity - Cowan 2001 found the capacity of the short term memory is 4 ± 1 items
• Evaluation of duration studies

  + High external validity Bahrick 1975 - investigated meaningful memories, Shepard 1967 found meaningless photos had lower recall rates

  x meaningless stimuli Peterson 1959 - numbers and consonant syllables have no personal meaning. Lacks external validity
• acoustic


  sound
• semantic


  meaning