Lecture 1 - Sensory Memory Flashcards
What is cognition?
The internal mental processes that are involved in making sense of the enormous amount of info that is bombarding our brains on a moment to moment basis.
The standard model of memory
Stimulus -> sensory register -> short term memory -> long term memory
- info lost at each three stages
- short term memory -> short term memory (REHEARSAL)
- long term memory -> short term memory (RETRIEVAL)
The sensory register function
- The retention, for a brief period of time, of the effects of sensory stimulation.
- sensory information is registered but only persists for a few seconds or less
Why don’t we attend to all of the sensory information?
we don’t actively attend to most of this information due to:
- info overload
- redundancy - don’t need all of this information
Visual sensory memory storage
Iconic storage: momentary memory for visual information.
-decays after 0.5 seconds
Auditory sensory information storage
Echoing storage: momentary memory for auditory information
-decays after 2 seconds
How to test for the capacity of sensory memory
- Sperling: The Whole-Report Procedure
- a stimulus is briefly presented (a grid of letters)
- participants to report as many letters as they remember
Findings of the Whole-Report Procedure
- participants could correctly report 4-5 items
- however, they were aware that there were actually more items being displayed than they could actually report.
- appeared that during the act of verbally reporting some of the items, the remaining items faded from sensory memory,
- suggests that the capacity of sensory memory is actually larger than that indicated by Sperling’s procedure. ( by approx. a third)
The Partial-Report Procedure
- the letter grid was presented briefly (as in the whole-report procedure)
- however, once the stimulus had disappeared from the screen, the participant heard one of three tones (low, med, high)
- if they heard high tone - asked to report letters from top line only (etc)
Findings of the Partial-Report procedure
- when participants were cued with a tone, they could report on average 3.3 of the four letters in the cued row (82%)
- important to note that the tone was presented AFTER the letters had disappeared from the screen.
- this means that the participant’s attention was not being directed to the actual letters in the stimulus - but to the MEMORY TRACE of the letters in the SENSORY STORE
The partial-report superiority effect
When the partial report procedure provides a superior estimate of the capacity of the sensory system than the whole report procedure.
How did Sperling measure the duration of iconic storage?
Delayed partial report procedure
The delayed partial report procedure
-used the Partial-Report procedure, but varied the length of time between the stimulus disappearing and the high/med/low cue tone.
Findings from the delayed partial report procedure
- as the duration between the stimulus disappearance and the cue tone increased, the proportion of info available to the participant decreased dramatically,
- conclusion: most of the info stored in iconic memory decays within 0.5 seconds.
Types of sensory information stored as shown by Sperling’s experiments
- iconic memory stores info about the physical characteristics of the stimuli (WHAT)
- also demonstrate that the iconic memory stores info about the relative positions of the stimuli. (WHERE)
Subsequent experiments finding’s from Sperling
- Found a partial report superiority for PHYSICAL characteristics such as colour, shape, size etc.
- participants didn’t show a partial report superiority when:
- asked to selectively report items from different SEMANTIC CATEGORIES such as number and letters
- asked to selectively report items based upon their sound characteristics such as an ‘ee’ sound (D, B, V, C) vs R, J, K etc
Conclusions from Sperling’s experiments and subsequent experiments
Suggests that info stored in iconic memory is visual and pre-categorical
Echoic sensory memory experiment
- stimuli presented orally and simultaneously across three separate channels (left, middle and right)
- visual cues indicated which channel was to be reported in the partial-report procedure
Findings of echoic sensory system experiments
- partial report superiority just like iconic memory
- echoic storage lasts for about 2 seconds (delayed partial response procedure)
- also, echoic memory doesn’t encode any semantic information, just physical characteristics of the sounds
Why is sensory memory so brief?
- to avoid sensory overlap
- if our iconic memory didn’t fade away quickly, the world would look like a horrible mess of overlapping images.
- if echoic memory didn’t fade away, noises would all overlap.
Persistence of visual imagery
A stimulus may no longer be physically present, but the image of the stimulus is still present (eg a film - 24 frames per second).
Implications visual persistence on Sperling’s findings
- perhaps were not accessing info stored in sensory memory, but rather we’re simply reading the residual image that persists for a brief period post-presentation.
- if this was true, the effect in question wasn’t a cognitive process but a much simpler physiological process.
General consensus now on Sperling’s findings
Generally agreed that iconic sensory memory isn’t just visual persistence.
-rather it appears to be a very brief store of sensory information - a Cognitive process, NOT a physiological process.
