Memory – Core Concepts

Memory Basics

• Memory = mental processes that encode, store, retrieve information over time.
• Defines personal identity; without it, cognitive function is severely limited.

Three Major Processes

• Encoding – transform input into storable form.
• Storage – retain data for later use.
• Retrieval – access stored data to conscious awareness.

Three-Stage Model

• Information moves sequentially through:
  • Sensory Memory → Short-Term Memory (STM) → Long-Term Memory (LTM).

Sensory Memory

• Function: brief overlap of sensory inputs → continuous perception.
• Iconic (visual): duration $0.25\text{–}0.5\,\text{s}$.
• Echoic (auditory): duration $3\text{–}4\,\text{s}$.

Short-Term Memory (STM)

• Workspace for conscious thought; receives from sensory & LTM.
• Duration: $\approx 20\,\text{s}$ (extended via maintenance rehearsal).
• Forgetting by decay & interference once attention shifts.

Capacity & Maintenance

• Classic limit: $7\pm2$ items (Miller); without chunking: $4\pm1$.
• Rehearsal: repeat to keep active.
• Chunking: group items to expand effective capacity.

Working Memory (Baddeley)

• Active STM system for reasoning & problem solving.
• Components:
  • Central Executive – controls attention, coordinates subsystems.
  • Phonological Loop – verbal material.
  • Visuospatial Sketchpad – visual/spatial data.
  • Episodic Buffer – integrates across modalities.
• Mental rotation studies show time ↑ linearly with rotation angle → active manipulation, not passive storage.

Serial Position Effect

• Recall curve shows better memory for first & last list items.
  • Primacy Effect – enhanced recall for early items.
  • Recency Effect – enhanced recall for late items.