Memory - features

• Short Term Memory (STM)

  The limited capacity memory store. Coding is mainly acoustic (sounds), capacity is between 5-9 items and duration is between 18-30 seconds.
• Long Term Memory (LTM)


  The permanent memory store. Coding is mainly semantic (meaning) it has unlimited capacity and can store memories for up to a lifetime.
• Coding


  When information comes into our memory system (from sensory input), it needs to be changed into a form that the memory system can cope with, so that it can be stored for later recall
• Coding formats


  • Visual (picture)
  • Acoustic (sound)
  • Semantic (meaning)
• Information is stored in different formats depending on the memory store that is being used
• Baddeley's research on coding


  1. Gave different lists of words to four groups of participants and asked them to remember the words

  2. Immediate recall (STM) - acoustically similar words were harder to recall

  3. Delayed recall (LTM) - semantically similar words were harder to recall
• Capacity


  The amount of information that can be held in a memory store
• Jacobs' digit span research


  1. Measured the digit span (capacity) of the STM by giving participants lists of digits to recall

  2. Found the mean span for digits was 9.3 items and for letters was 7.3 items
• Span of Memory and Chunking

  • The capacity of the STM is an average of 7 items (5-9 items)
  • We can recall more by grouping items into chunks
• Duration


  The length of time information can be held in our memory stores
• Peterson & Peterson's research on STM duration


  1. Tested 24 undergraduate students

  2. Gave them a trigram (3 letter syllable) and asked them to count backwards to prevent rehearsal

  3. Tested recall after different time intervals (3, 6, 9, 12, 15, 18 seconds)

  4. Found STM duration is around 18-30 seconds
• Bahrick et al.'s research on LTM duration


  1. Studied 392 participants aged 17-74

  2. Used high school yearbook photos and free recall tests

  3. Found photo recognition was 90% accurate within 15 years, dropping to 70% after 48 years

  4. Free recall was 60% accurate after 15 years, dropping to 30% after 48 years
• :( Lacked mundane realism


  Baddeley's research

  • Memorising a word list had no relation to the participants real-life memory
  • Artificial task
• :) Well controlled


  Baddeley's pps experienced the same procedures

  • Seeing each word for 3 seconds on a projector
• :( Lacked control over extraneous and confounding

  variables


  Jacobs

  • experiments lacked control, which saw pps become distracted while they were being tested so they may not have performed as well.
• :( Over-estimated capacity of STM


  Jacob's

  • Cowan (2001) reviewed the research and concluded that the capacity of the STM was only about four chunks of information
  • Miller's 5 +/- 7 is more accurate
• :( Order effects


  Peterson + Peterson

  • repeated measures design
  • results due to pps becoming fatigued at learning the nonsense trigrams, meaning accuracy of recall became worse as the trials went on
• :) High external validity


  Bahrick's study

  • real-life meaningful memories associated to people pps attended high school with, were studied rather than artificial stimuli