Short-Term Memory Notes

What is Memory?

  • Memory involves retaining, retrieving, and using information about stimuli, images, events, ideas, and skills after the original information is no longer present.
  • It's an active process where past experiences impact current thoughts or behaviors.

Modal Model of Memory

  • Developed by Atkinson and Shiffrin (1968).
  • Includes three types of memory:
    1. Sensory Memory: Holds incoming information for a fraction of a second.
    2. Short-term Memory: Holds 5-7 items for about 15-20 seconds.
    3. Long-term Memory: Holds a large amount of information for years or decades.
  • Control processes are active processes controlled by the person, such as:
    • Strategies of attention (selective attention).
    • Strategies to make stimuli more memorable (cues, heuristics).
    • Rehearsal: Repeating information.

Sensory Memory

  • Retains effects of sensory stimulation for brief periods.
  • Holds a large amount of information for initial processing, but decays quickly.
  • Allows us to experience the world as a continuous stream.
  • Early evidence includes persistence of vision (e.g., sparkler's trail of light).
  • Sperling (1960) measured capacity and duration using flashed letters.
    • Whole report method: Participants reported an average of 4.5 out of 12 letters (37.5%).
    • Partial report method: Participants reported an average of 3.3 out of 4 letters (82%).
    • Delayed partial report method: Performance decreased, remembering 1 out of 4 (25%) after a 1-second delay.
    • Conclusion: Sensory memory is short-lived, less than a second.
  • Iconic memory: Brief sensory memory of visual information lasting 200-500 milliseconds, holding up to 12 items.
  • Echoic memory: Brief sensory memory of auditory information lasting less than a second, possibly up to 3-4 seconds.
  • Visual masking can disrupt iconic memory. Presenting a visual stimulus (mask) shortly after the initial stimulus.
  • Auditory masking, noise interference, and rapid presentation can disrupt echoic memory.

Short-Term Memory

  • Stores small amounts of information (5-7 items) for a brief period.
  • Includes new information from sensory stores and old information from long-term memory.
  • Peterson & Peterson (1959) measured duration by having participants recall letters after counting backward.
    • After 3 seconds, performance was at 80%; after 18 seconds, it was at 10%.
    • Decay is the vanishing of a memory trace due to time and competing stimuli.
    • Conclusion: Short-term memory lasts about 15-20 seconds when rehearsal is prevented.
  • Capacity is measured by digit span; typical result is 5-7 items.
  • George Miller (1956) found capacity to be 7 +/- 2 items or “chunks”.
  • Chunking: Combining small units into larger meaningful units.
    • Strong association within chunks, weak association across chunks.
  • Ericsson et al. (1980) demonstrated that with training, a person could remember up to 79 digits by chunking them into meaningful units.