IBP: Introduction to cognitive psychology

Chapter 5: short-term memory

Long-term memory (LTM): memory held in permanent storage, available for retrieval at some time in the future

Short-term memory (STM): memory held in conscious awareness, and which is currently receiving attention

Dual-store model of memory: the concept of the STM as a conscious workspace. The distinction between STM and LTM is sometimes referred to as the ‘dual-store’ theory of memory, because it proposes two distinct forms of memory storage

Evidence for the distinction between STM and LTM:

• STM can remain intact despite severe impairment of LTM (organic amnesia) or vice versa
• Digit span: A measure of STM, largest number of digits which can be recalled when tested immediately after their presentation
  • tests capacity of the phonological loop (〜 7 digits)
• Recency and primary effects: tendency for participants to show particularly good recall for items presented towards the end (recency) or the start (primacy) of a list
• STM storage requires rehearsal; when rehearsal prevented, the information is rapidly forgotten

Working memory: hypothetical short-term memory system that serves as a mental workspace in which a variety of processing operations on both new input and retrieved memories

• STM is seen as active working memory
• LTM is seen as a storage memory which maintains information in a fairly passive state for possible future retrieval
• Working memory has separate stores for visual and auditory information:
  • Central executive: overall control of working memory: decision-making, problem-solving, selective attention
  • Phonological loop: holds auditory and speech-based information
  •  Visuo-spatial sketchpad: holds visual information

The phonological loop: A hypothetical component of working memory, which is assumed to provide brief storage for verbally presented items

• Main evidence for phonological loop: dual task paradigm
  • Performing a second verbal task disrupts the first one because they are both competing for the limited storage space in the phonological loop
  • A visual WM task and an auditory WM task can be carried out simultaneously without disrupting each other
• Articulatory suppression: A task used to occupy the articulatory control process of the working memory, normally involving the repetition of a sound (such as “the”) which requires articulation but little processing.
• Phonological store: stores auditory information
• Word-length effect: word span limit is greater for short words than for long words
• Articulatory control process: sub-vocal rehearsal of the information (inner speech mechanism)

The visuo-spatial sketchpad

• Can be measured by the number of visually presented objects you can hold consciously at one moment
• Visual cache: stores visual information about shapes and colors
• Inner scribe: holds spatial information and assists with the control of physical actions

The central executive: is thought to have overall control of cognitive processing, and it is probably the main focus of conscious awareness.

• Controls the phonological and visuo-spatial loops, and uses them to help with processing
• Three main functions: inhibition, shifting, updating
• Dysexecutive syndrome: frontal lobe lesions which lead to an impairment of central executive function
  • May include: impaired concentration/ concept formation/disinhibition/ inflexibility/perseveration/ impaired cognitive estimation/ impaired strategy formation

Working memory theory today

• Problem: by fractionating the working memory into a number of separate memory loops dedicated to specific sense modalities, it offers no clear explanation of how information from the visual and phonological loops can be combined and linked to multimodular information in the LTM
• Solution: Episodic buffer - A hypothetical component of working memory which integrates information from different sense modalities, and provides a link with the LTM
• Thories:
  • Feature model: working memory retrieval depends on matching the features of a WM trace with those of a storage memory trace, the main limitation being that the SM trace is degraded by interference
  • Controlled attention theory: working memory consists of the temporary activation of a part of the storage memory, rather than being a totally separate system
• Parts of the brain involved in the activities of the working memory:
  • Verbal tasks: left hemisphere
  •  Visuo-spatial tasks: right hemisphere
  • Phonological store: supramarginal gyrus (edge of the left parietal lobe)
  • Articulatory control process: part of Broca’s area in the left frontal cortex

Resources: An Introduction to Cognitive Psychology: Processes and Disorders 3rd edition (Groome, David)