Chapter 3: Short-term Memory

Short-Term Memory (STM) and Working Memory (WM)

• STM refers to the temporary storage of small amounts of information.

• WM is a complex system for storing and manipulating information.

Childhood Memory Example

• Scenario: Teacher instructs students on actions to follow. Some pupils comply, while others show confusion.

• Reason: Difficulty in processing and retaining multi-step instructions due to short-term memory limitations.

Historical Context: Digit Span Test

• John Jacobs (1887): Created a test to assess students' memory using sequences of digits.

• Digit Span: The maximum number of digits a person can accurately recall in order.

• Current Use: Digit span is included in many intelligence tests, like WAIS.

Difference Between STM and WM

• Short-Term Memory (STM): Involves simple retention tasks, either immediate or after brief delays.

• Working Memory (WM): Involves temporary storage and manipulation of information, necessary for reasoning and comprehension.

The Multicomponent Model of WM

• STM is part of the broader WM system, which is essential for complex cognitive tasks.

• Models influenced by varying factors such as attention, individual differences, and neurophysiology (Cowan, 2001; Engle & Kane, 2004; Goldman-Rakic, 1996).

Memory Span and Capacity

• Typical Span: Generally limited to 7±2 items (Miller, 1956).

• Capacity varies based on familiarity with items and contextual factors.

  • Chunking: Breaking down information into small, manageable chunks can aid recall (e.g., grouping letters or digits).

Short-Term Memory Tasks

Digit Span as a Task

• The process mimics recalling phone numbers:

  1. Remember items.

  2. Recall order of presentation.

• Longer and complex items lower recall success.

Phonological Loop Concept

• Phonological Loop: Component of Baddeley and Hitch's model responsible for the temporary storage of verbal information through rehearsal.

• Explains several memory phenomena, including:

  • Phonological similarity effect: Similar-sounding items are harder to recall.

  • Word length effect: Longer words result in reduced memory span due to rehearsal time.

Irrelevant Sound Effect

• Disruption of STM by background noise/speech, due to phonological similarity.

• Music interferes with recall performance, particularly vocal music.

Visual and Spatial Short-Term Memory

Visual STM

• Limited to 3 to 4 items, can be influenced by complexity of those items.

• Change Detection Task: Used to study how many visual items people can hold in memory.

  • Research by Luck & Vogel (1997): Found steep performance decline as number of items increased.

Differences in Memory Types

• Spatial vs Visual Memory:

  • Spatial Memory: Focused on locations and movements (e.g., Corsi Block Tapping Test).

  • Visual Memory: Centers on colors and shapes.

• Research shows different neural pathways for visual and spatial STM, indicating that they can operate independently.

Neuropsychological Evidence

• Patient Studies: Insights drawn from patients with specific memory deficits:

  • Patient KF: Deficits primarily in verbal STM, strong visual memory.

  • Patients L and MV: Mixed performance highlighting independence of visual vs spatial STM.

Summary of Key Points

• STM and WM play critical roles in cognitive functions.

• Multi-faceted and influenced by a variety of factors, including item complexity, type of information, and individual differences.

• Experiments using simple stimuli (digits, characters) provide insights into STM processes, while patient studies highlight the complexities involved in memory functions.