Cognitive Psychology Class Notes > Short-Term Memory

Sensory Memory

• permits the trace of a stimulus to "linger on" for further processing

Why Sensory Memory?

• we need to integrate information across time and space

• we need to keep a brief record in order to select important stimuli for further processing (e.g. selective attention)

• may provide a stability to visual world despite constant eye movement

Types of Sensory Memory

• iconic memory: visual sensory memory

• echoic memory: auditory sensory memory

Iconic Memory

• visual information = icon
• visual information automatically registered in iconic memory
• Duration = icon lasts .5 s

Sperling (1960)

Hypothesis: mental picture of display disappeared / faded by the time you were able to respond

Design: whole report (report all items)

partial report (Ss heard high, med. or low tone; they reported corresponding top, middle, or bottom row of display)

Results: whole report = 4.5 items

partial report = 9 items

(accuracy rate X # letters in display)

(100% X 9 items = 9 items)

in partial report, with longer delays between stimulus presentation and sounding of the tone to report, accuracy decreased to 4.5 items (whole report levels) Fig. 4.1

Conclusion: icon fades after 1/2 second

provides a framework for info-processing - info is held for a brief amount of time before that info is processed further (stages of processing - Atkinson-Shiffrin)

Echoic Memory

• auditory information = echo
• auditory information automatically registered in echoic memory
• Duration = echo lasts 2 s

Darwin, Turvey, Crowder (1972)

• 'three eared man' procedure (adaptation of Sperling's procedure)J 4 T 3 M Z A 5 2 (simultaneous presentation)| | |left middle right
• replicated Sperling's pattern of results, but maximum number of items recalled was 5 items and echo lasted for 2 s

Short-Term Memory

Theoretical Aspects:

• proactive interference
• span of STM
• chunking

• temporary storage of information: we forget information from STM after 30 seconds (unless we rehearse)
• limited capacity (two views):

• number of units:
  • digit span & the WAIS-III
  • Miller's Magic Number
  • 7 plus or minus 2
  • items can be organized into larger units called chunks

• pronunciation times:
  • verbal trace endures for a limited time

Chad, Sweden, Greece, Cuba, Malta --> 4.2 items recalled

Indonesia, Somalia, Afghanistan, Argentina, Venezuela --> 2.8

Two Types of Chunking

1 4 9 1 6 2 5 3 6 4 9 6 4 8 1

• combine items that are close together in time or space

1491 625 3649 6481

• utilize information from LTM

1 4 9 16 25 36 49 64 81

Proactive Inhibition (Interference)

• old material interferes forward in time learning new material
• PI occurs only with related material
• Practical Example: abnormal psych & theories of personality

Release from PI

• if one changes the learning material to unrelated material, performance on memory tests returns to normal
• Practical Example: studying same material...take a break!!