Structure of Short Term Memory

Baddeley's Model of Working Memory


Baddeley's model is an alternative to the Attkinson and Shiffrin model; it has four components:

  • The Central Executive (supervises the flow of information to and from slave systems)
  • Phonological Loop (short term verbal storage system)
  • Visuo-Spatial Sketchpad (short term visuo-spatial storage system)
  • Episodic Buffer (system for linking information across domains to form integrated spatial/visual/verbal/chronological units).

The Central Executive

The Central Executive controls resources and treats the other three components as slaves, deciding when and where to recruit and use them.

Its jobs are to:

  • Co-ordinate the slave systems
  • Collect and group information from multiple sources, maintaining attention to goal-relevant content.
  • Decide how best to achieve goals with its information
  • Inhibit inappropriate (not goal relevant) automatic responses (habits)
  • Shift between tasks and retrieval strategies

It essentially follows Mazlow's Hierarcy of needs (immediate goals like food and shelter and warmth are put above trying to pass the exam). It suppresses undesirable or inappropriate behaviours (although sometimes things like OCD means it fails and allows habits to undermine your goal).

The central executive lives in the frontal lobe, and damage to that area makes us annoyed, cranky and prone to risky, impulsive and thoughtless behaviours. As this is one of the last places to be developed, teenagers often haven't developed it yet.

Phonological Loop

The phonological loop deals with sounds - all phonological input is processed through its two parts:

  • The Inner Ear: short term storage - words/speech sounds can be remembered in chronological order.
  • The Inner Voice: articulatory rehearsal unit which can repeat words/speech elements on a loop to prevent them from decaying.


We have a limited capacity for storage - $7 \pm 2$; if we add too many things to a spoken list things start to fall off. What's interesting is that storing bigger things means our capacity is less. This explains why Welsh-speakers often find it harder to recall numbers than English-speakers (the Welsh words for numbers are longer).

Strategies for Improving Storage Numbers

(See wikipedia on this).

  • Buckets/Chunking - grouping information in familiar ways (e.g. phone numbers or anagrams)
  • Rearrange things to reduce the number of items
  • Say things that sound different (semantic similarity is irrelevant, the phonological storage means similar sounding things get confused).

Visuo-Spatial Scratch Pad

The visuospatial sketchpad is assumed to hold information about what we see. It is used in the temporary storage and manipulation of spatial and visual information, such as remembering shapes and colours, or the location or speed of objects in space. It is also involved in tasks which involve planning of spatial movements, like planning one's way through a complex building.

It's essentially the mind's eye; a place to jot down 3d pictures of things we want to note.

Episodic Buffer

This was only added in 2000, and Psych didn't explicitly teach it. Essentially thanks to patients with amnesia we know that people without the ability to encode new long term memories have better-than-expected ability to tell stories - which is where the episodic buffer's linking skills come in.