Memory -- Working Memory Model

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Put together by...

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Baddeley and Hitch (1974)

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Working memory refers to...

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that bit of memory that you are using when you are working on a complex task which requires you to store information as you go along.

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Baddeley and Hitch felt that STM was not just one store but a numbers of different stores because...

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> if you do 2 things at the same time and they are both visual tasks, you perform them less well than if you do them separately

> if you do 2 things at the same time and one is visual whereas the other involves sound, then there is no interference. You do them as well simultaneously as you would do them separately.

Suggests that there is one store for visual processing and one store for processing sounds, as portrayed by the model.

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The Working Memory Model

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Central Executive

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>the key component of working memory

>its function is to direct attention to particular tasks, determining at any time how 'resources' are allocated to tasks.

>the resources are the three slave systems below the CE

>data arrives from the senses or from LTM

VERY LIMITED capacity -- can't attend to too many things at once

Monitors are coordinates all other mental functions in working memory.

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Phonological Loop

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>deals with auditory information and preserves the order of information

>Baddeley (1986) further subdivided this loop into the phonological store and an articulatory process

>the phonological store holds the words you hear, like an 'inner-ear'

>the articulatory process is used for words that are heard or seen. These words are silently repeated (looped), like an 'inner-voice', a form of maintenance rehearsal.

Encodes speech sounds in working memory, typically involving maintenance rehearsal (repeating the words over and over again). This is why this component of working memory is referred to as a 'loop'.

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The Visuo-spatial Sketchpad

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>used when you have to plan a spatial task (e.g, getting from one room to another, or counting the number of windows in your house)

>visuo and/or spatial info is temporarily stored here

>visual information: what things look like

>spatial information: the relationship between things

E.G Imagine an egg (visual info) spinning in mid air inside your bedroom (spatial info).

Logie (1995) suggested that the visuo-spatial sketchpad be divided into a visual cache (store) and inner scribe which deals with spatial relations.

Encodes visual information in terms of separate objects as well as the arrangement of these objects in one's visual field.

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Episodic Buffer

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>Baddeley (2000) added the EB because he realized the model needed a general store

> the PL and V-SS deal with processing and temporary storage of specific kinds of info. The CE has no storage capacity. So there was nowhere to hold info that related to both visual and acoustic info.

> the EB is an extra storage system that has, in common with all the working memory units, limited capacity.

> integrates info from the CE, the PL and the V-SS and also from LTM.

Receives input from many sources, temporarily stores this information, and then integrates it in order to construct a mental episode of what is being experiences right now.

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STRENTHS of WMM

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> fMRI shows central executive more active when two tasks done (Bunge et al.)

> Explains word-length effect (Baddeley et al.)

> Visuo-spatial sketchpad shown in visual tracking task (Baddeley et al.)

> Episodic buffer shown comparing recall of related and unrelated words (Baddeley et al.)

> Explains memory deficits of KF and SC.

> Maintenance rehearsal is only an optional process.

> Emphasizes process rather than structure.

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LIMITATIONS of WMM

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> Central Executive doesn't actually explain anything.

> Central Executive is probably several components (Eslinger and Damasio).

> Problems with evidence from brain-damaged individuals, e.g, no before and after comparisons.

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EVIDENCE FOR THE CENTRAL EXECUTIVE

Bunge et al. (2000)

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Used fMRI to see which parts of the brain were most active when ppts were doing two tasks (reading a sentence and recalling the final word in each sentence).

The same brain areas were active in dual- or single-task conditions but there was significantly more activation in the dual-task condition indicating that increased attentional demands were reflected in brain activity.

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Hitch and Baddeley (1976)

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Gave ppts two tasks to do simultaneously. Task 1: occupied the CE. Task 2: either involved the articulatory loop or both the CE AND the articulatory loop, or no additional task.

Task 1 was slower when given a task involving both the CE and the articulatory loop.

Speed on task 1 was the same whether using the articulatory loop or no extra task.

Shows that doing two tasks that involve the same component causes difficulty.

Suggests that when different components are used, performance is not affected.

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Word-length effect

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The observation that people remember lists of short words better than lists of long words.

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EVIDENCE FOR THE PHONOLOGICAL LOOP

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> the word-length effect

> seems that the PL holds the amount of info that you can say in 2 seconds (Baddeley et al, 1975a)

> makes it hard to remember a list of long words compared to shorter words. The longer words can't be rehearsed on the PL because they don't fit.

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EVIDENCE FOR THE ARTICULATORY PROCESS

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The word-length effect disappears if a person is given an articulatory suppression task.

E.g., you are asked to say "the the the" while reading the words.

This repetitive task ties up the articulatory process and means you can't rehearse the shorter words more quickly than the longer ones, so the word-length effect disappears.

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EVIDENCE FOR THE VISUAL-SPATIAL SKETCHPAD

Baddeley et al. (1975b)

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Ppts were given a visual tracking task (tracking a moving light with a pointer).

At the same time they were given one of two other tasks:

> task 1: describe all the angles on the letter F

> task 2: perform a verbal task

Task 1 was very difficult but not task 2, presumably because the 2nd task involved two diff. components (or slave systems).

ALSO evidence related to the effects of doing two tasks using the same or diff. components.

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EVIDENCE FOR THE EPISODIC BUFFER

Baddeley et al. (1987)

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Found that when ppts were shown words and then asked for immediate recall, their performance was much better for sentences (related words) than for unrelated words.

Supports the idea of an immediate memory store for items that are neither visual nor phonological and that draw on LTM (to link the related words).

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EVIDENCE FROM BRAIN DAMAGED PATIENTS

KF - Shallice and Warrington 1970

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His short term forgetting of auditory info was much greater than that of visual stimuli, and his auditory problems were limited in respect of verbal material such as letters and digits but not of meaningful sounds (such as a phone ringing).

Thus his brain damage seemed to be restricted to the phonological loop.

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EVIDENCE FROM BRAIN DAMAGED PATIENTS

SC - Trojano and Grossi, 1995

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Had generally good learning abilities with the exception of being unable to learn word pairs that were presented out loud.

Suggests damage to the phonological loop.

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EVIDENCE FROM BRAIN DAMAGED PATIENTS

LH - Farah et al, 1988

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Had been involved in a road accident, performed better on spatial tasks than those involving visual imagery.

Suggests separate visual and spatial systems.

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Park et al, (1999)

(strength of model)

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Reviewed a number of studies and concluded that problems with working memory were a key distinction between normal individuals and patients with schizophrenia.

The concept of working memory is one means by which schizophrenia can be diagnosed.