Cognitive Psychology (PSYC 110) · Module 2 of 10
Short-Term & Working Memory
The limited-capacity system that holds information active, and Baddeley's model of how it's organized.
Short-Term Memory Capacity
- Short-term memory (STM) has a limited capacity, often cited as "7 ± 2" items (Miller, 1956), though later research (Cowan) suggests closer to about 4 chunks without rehearsal.
- Chunking — grouping individual items into larger, meaningful units — increases the effective amount of information STM can hold.
How does chunking increase the effective capacity of short-term memory?
Solution. By grouping individual pieces of information into larger, meaningful units, a person can hold more total information within the same limited number of "slots," since each chunk still counts as roughly one unit.
Baddeley's Working Memory Model: Structure
- Baddeley and Hitch's model replaced the single-store idea of STM with a multi-component "working memory": a central executive that coordinates two subsystems, and later, an added episodic buffer.
- The phonological loop handles verbal/auditory information; the visuospatial sketchpad handles visual and spatial information.
What was the main limitation of the older single-store model of short-term memory that Baddeley and Hitch's working memory model addressed?
Solution. A single-store model couldn't easily explain how people can hold and manipulate different types of information (verbal and visual) at once with minimal interference; the multi-component model explains this with separate subsystems for each.
The Central Executive & Episodic Buffer
- The central executive is an attention-controlling system that coordinates the subsystems, directs attention, and manages tasks — but has no storage capacity of its own.
- The episodic buffer, added later, integrates information from the phonological loop, visuospatial sketchpad, and long-term memory into a single, unified representation.
What is the role of the central executive in Baddeley's working memory model?
Solution. It acts as an attentional control system, coordinating and directing the activities of the phonological loop and visuospatial sketchpad and allocating attention between tasks, but it does not store information itself.
Evidence for Separate Subsystems
- Dual-task studies support separate subsystems: performing two tasks that both rely on the same subsystem, like two verbal tasks, impairs performance more than combining tasks relying on different subsystems.
What kind of evidence supports the idea that the phonological loop and visuospatial sketchpad are separate systems?
Solution. Dual-task studies show that combining two verbal tasks causes much more interference than combining a verbal task with a visual/spatial task, suggesting the two subsystems have largely independent capacities.
Check yourself
2 of this module's 5 quiz questions. Pick your answers, then check them in the app, with an explanation for every question.
1. What is the classic estimate of short-term memory capacity?
2. What does chunking do?