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Short and long term memory

• Capacity
  • Jacobs - digit span 9.3 for digits, 7.3 for letters
  • Miller - people remember about 7 items and 7 chunks
  • Evaluation
    • Cowan - 4 chunks probably the limit. Same for visual information (Vogel et al)
    • Simon - larger chunks means fewer recalled
    • Jacobs - digit span for 19 year olds is 8.6 compared to 6.6 for 8 year olds
• Duration
  • Peterson and Peterson - used consonant syllables, prevented verbal rehearsal. STM lasted 18 seconds
  • Bahrick et al - after 48 years, participants were 70% accurate in face recognition of classmates and 30% for names
  • Evaluation
    • Consonant syllables not meaningful but some memory activities do involve such stimuli
    • Reitman - auditory tones to avoid displacement, led to longer duration of STM
    • Nairne et al - duration for STM 96 seconds
• Coding
  • Baddeley - difficulty remembering acoustically similar words in STM but not in LTM, reverse for semantically similar words
  • Evaluation
    • In Baddeley's study LTM was tested by waiting 20 minutes which isn't LTM
    • Brandimote et al - STMs visually coded if verbal rehearsal prevented
    • Wickens et al - STM sometimes uses a semantic code
    • Frost - visual coding in LTM
    • Nelson and Rothbart - acoustic coding in LTM

The multi-store model of memory

• Sensory register - large capacity, very short duration
• Attention transfers info from sensory register to STM
• STM - Limited capacity so info decays, limited duration unless rehearsed
• Maintenance rehearsal eventually creates a LTM
• LTM - unlimited capacity and duration, forgetting may be due to lack of accessibility
• Retrieval from LTM goes through STM
• Evaluation
  • Strengths
    • Lots of lab studies to support it
    • Brain scans e.g. Beardsley linked STM to prefrontal cortex, Squire et al linked LTM to hippocampus
    • Case study of HM - linked formation of new LTMs to hippocampus
  • Weaknesses
    • It is too simple, STM and LTM are not unitary stores
    • LTM involves elaborative rather than just maintenance rehearsal

The working memory model

• Central executive acts as 'attention', allocates tasks to slave systems, no storage
• Phonological loop preserves order of auditory information
  • Phonological store holds the words for the PL, inner ear
  • Articulatory process performs maintenance rehearsal for PL, inner voice
• Visuo-spatial sketchpad for planning and processing visual and/or spatial tasks
  • Visual cache for form and colour
  • Inner scribe for spatial relations
• Episodic buffer records events as they happens, links to LTM
• Evaluation
  • Strengths
    • Hitch and Baddeley - participants slower when doing dual tasks. Demonstrates CE
    • KF - damage to PL, problems with verbal material (Shallice and Warrington)
    • SC - damage to PL, unable to learn word pairs presented out loud (Trojano and Grossi)
    • LH - damage to spatial system (Farah et al)
  • Limitations
    • CE doesn't explain anything and more complex than currently represented, evidence from EVR (Eslinger and Damasio)
    • Brain damage evidence unreliable because trauma may cause problems

Types of LTM

• Episodic memories - personal memories for events
  • They include details of context and emotion
• Semantic memories - knowledge shared by everyone
• Procedural memories - knowing how to do something
  • They become automatic through repetition
• Evaluation