Cognition, lecture 4: Memory

Cognition, lecture 4: Memory

1. What is memory?

   • The process of storing information and experiences for possible future retrieval.

2. Early thoughts on multiple memory stores

   • William James
     • Primary memory: information that remains in the consciousness after is has been perceived.
       • Secondary memory: Information about events that have left consciousness
   • Hernmann Ebbinghaus
     • Conducted all his experiments on himself.

3. Multi-store memory model:

   • Sensory store - high capacity but v short term.
     • STM - capactiy of 7 +/- 2
       • LTM - supposedly unlimited capacity
   • By Atkinson and Shiffrin

4. Differences in the memory stores

   • The serial position curve:
   • Tested by a free recall task: words presented at a fixed rate then recalled in any order
   • Better recall for earlier and later items than those in the middle
   • The recency effect: The last few items are recalled well because they're still in the ppts STM
     • This was tested by adding delay before recall and recency effect diminished
   • The primacy effect: The first few items were rehearsed more and so worked into the LTM
     • Delay didn't effect primacy effect
   • Short term memory
     • Miller - capacity = magic number: 7 +/- 2. (diget span task)
     • Use of 'chunking' to improve memory - putting into smaller meaningful segments
       • Peterson and Peterson - Trigrams and delay with no rehearsal (recall dips after 20s)
     • Phonological confusability effect: visually presented letters had worse recall than on similarly sounding letters
       • STS info is stored used phonological coding
   • Long term memory
     • Capacity is thought to be limitless
     • Semantic confusability effect: delayed recall - worse performance if words were semantically similar
       • Info in LTM stored using semantic coding
   • Sensory store
     • Iconic store
       • Visual store
       • Duration - 500ms
       • Capacity - 12+ letters
       • Loss via decay
     • Echoic store
       • Auditory store
       • Duration - 1-5 seconds
       • Capactiy depends on stimuli
     • Loss via decay
     • Evidence
       • Patient 'HM'

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