The Working Memory Model

Central Executive

Baddeley & Hitch (1974)

  • focused on STM
  • LTM more passive store that holds previously
    learned material for use by STM when needed
  • acts like attention
  • limited capacity
  • determines how resources (slave systems) are allocated
  • involved with reasoning & decision making tasks
  • Baddeley (1986) - metaphor - 'company boss'
  • modality free (not coded by sense)

1st Slave System
Phonological Loop

  • consists of:
    • Phonological Store (inner ear)
    • Articulatory process (inner voice)
  • limited capacity
  • deals with auditory information
  • preserves word order-inner ear

Episodic Buffer

2nd Slave System
Visuo-Spatial Sketchpad

  • visual & spatial info is stored her - inner ear
  • limited capacity - 3-4 objects
  • Logie (1995) suggested subdivision
    • visuo- cache store & inner scribe for spatial relations
  • model needed more general store
  • extra storage system (limited capacity of 4 chunks)
  • integrates info from all areas
  • modality free

STUDIES

Baddeley & Hitch (1976)

  • gave participants 2 tasks to perform simultaneously
  • asked to say 'the the the' (involves articulatory loop)
  • asked to say random digits ) involves central executive & articulatory loop)
    Results
  • true/false task was slower when given 2nd task involving central executive & articulatory loop
    Conclusions
  • completing 2 tasks that involve same component causes difficulty
  • supports central executive & WMM

Bunge et al (2000)

  • used fMRI to see which parts of brain were most active when participants were doing a verbal & visual task
  • same brain ares (pre-frontal cortex) were active in either dual & single task conditions
    • but there was significantly more activation in dual task condition

Word-length effect (WLE)

  • phonological loop explains why WLE occurs
  • fact that people cope better with short words than long words in WM (STM)
  • phonological loop holds amount of info that you can say in 1.5-2 seconds
    • hard to remember list of long words
  • WLE disappears if person is given an articulatory suppression task (e.g. 'the the the' while reading words)
  • repetitive task ties up articulatory process - means you can't rehearse shorter words more quickly than longer ones

EVALUATION

Clinical Evidence

!STRENGTH!

  • Shallice & Warrington's (1970) case study of patient KF
  • after brain injury, KF had poor STM ability for auditory info
    • but could process visual info normally
  • e.g. immediate recall of letters/digits was better when he read them (visual) than when they were read to him (acoustic)
  • KF's phonological loop was damaged but visuo-spatial sketchpad was intact
  • finding strongly supports existence of separate visual & acoustic memory stores

HOWEVER

  • unclear whether KF had other cognitive impairments which may have affected his performance on memory tasks
  • e.g. injury caused by motorcycle accident - trauma involved may have affected his cognitive performance
  • this challenges evidence that comes from clinical studoes of people with brain injuries that may have affected many different systems

Dual-task Performance

!STRENGTH!

  • studies of DTP support separate existence of visuo-spatial sketchpad
  • Baddeley et al (1975) participants carried out visual & verbal task at same time (DT) - performance on each was similar to when carried out tasks seperately
  • but when both tasks where visual/verbal - performance declined substantially
  • because both visual tasks for the same subsystem (VSS), whereas there is no competition when performing verbal & visual task together
  • shows there must be a separate subsystem (VSS) that processes visual input & one for verbal processing (PL)

Nature of Central Executive

!LIMITATION!

  • lack of clarity over nature of CE
  • Baddeley (2003) recognised this when he said:
    • 'The central executive is the most important but the least understood component of working memory'
  • CE needs to be more clearly specified than just being simply 'attention'
  • means CE is an unsatisfactory component & this challenges integrity of WMM