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Lecture

Psychology 2135A/B Lecture Notes - Iconic Memory, Sensory Memory, Middle Ear


Department
Psychology
Course Code
PSYCH 2135A/B
Professor
Robert Brown

Page:
of 3
Lecture 6 - Memory
Why does memory exist?
- one way for a species to store the information it needs for survival is in DNA
- DNA works for information acquired over the life-time of the species; relatively consistent over
life-time of species
- DNA deals with aspects of world that are consistent over very long time periods
- memory exists because DNA is not enough; DNA is for things consistent over long periods;
memory and learning for things that change over short periods of time
Consider three possible types of world
First, a completely random world
- nothing is predictable
- animals could be predators one day, prey the next
- storing information about world would be pointless
A completely systematic world
- everything totally predictable
- predators equally distributed in every direction, food always in same place
- then, all responses could be coded into DNA and learning during your life would not be
necessary
A partially random, partially systematic world (real world)
- some variation, with an underlying trend
- memory makes sense; change things on a smaller time scale but not worth to be in DNA
Moral of the story
- there is structure in the world
- makes sense for our behaviour to be guided by that structure
- some of that structure changes slowly, so it is in DNA
- some changes quickly so information is acquired in lifetime of individual and in memoir
- Definition: any response that occurs after a stimulus has disappeared is based on memory
How are people different from animals?
- our enormous repertoire of behaviours, and the large memory store that supports it
- we recognize a huge number of different objects in the world
- any pair of these objects has meaningful differences
- categorize objects in many different ways and we can make up new categories any time
How do we select the adaptive responses?
- large repertoire of behaviours; recognize many different objects
- How can we match a behaviour to object drawing our attention?
- create representation of what is out there (stimulus representation)
- compare representation to all stored representations in memory to find out what the thing is and
how to respond to it
Why is that process challenging?
- in dynamic world, stimuli arrive and leave suddenly
- if you do not recognize fast, may get eaten or may not eat it
- recognize means retrieve the right representation from among all those in memory
- retrieve fast due to a dynamic world
How do we get information out of memory?
- use memory stores with different operating characteristics
- sensory, short-term, long-term
- have different strengths and weaknesses
- human cognition is the sum of a series of solution to "engineering problems" through evolution
Sensory Memory
- very short duration
- difficult to measure capacity
- Sperling's experiment only had letters
- a record of environmental energy arriving at the sense receptors (e.g., retinas, ears...)
- contains raw (unprocessed) - no objects, no features, just the stimuli energy (wavelengths of
light, sound energy at different frequencies of air pressure waves, etc.)
- never recognize object in sensory memory since it is just raw
- keeps things around long enough for transfer to short-term memory
- unavailable to consciousness
Short-term memory [Working memory]
- short duration - lasts up to about 15 seconds
- rehearsing can keep things indefinitely in short-term memory (phone numbers)
- very small capacity: 7 +/- 2 chunks
- fast access - encoding and retrieval
- processed stimuli - not just light/sound waves etc.
- keeps things around long enough for encoding into long term memory to begin
- where thinking occurs
Long-term memory
- unlimited capacity (can always learn)
- lifelong duration (barring insult to brain); permastore: memory that is never lost
- significant time required for consolidation (about 2 hours; found from people in accidents,
could never remember 2 hours before accident)
- longer retrieval times than for STM
- basis for guided behaviour - LTM allows us to learn, store, and apply lessons about the world
Interim Review
- memory system allows us to:
- take in information about a swiftly changing stimulus array
- recognize any of thousands of items in many categories
- retrieve relevant information
- update memory files with information about most recent experience with a stimulus
The standard model of memory
world -> sensory memory -> attention -> working memory <-> long term memory
or -> forgotten
Questions about sensory memory
- different sensory memory stores for the different senses
- what is the capacity of the sensory store?
- what is the duration of traces in the sensory store?
- most research done with visual and auditory
Sperling's Partial Report Task
- before Sperling, task was always report all letters in display
- suggested that when reporting first few letters, the other letters in sensory memory would decay
and disappear
- partial report had people report only 1 row after random tone
- prediction: if just chose to remember one row, should remember 1/3 times x 4 letters = average
of 1.33 letters; if able to remember whole display, should remember 3/3 times x 3-4 letters =
average of 3-4 letters
- used tones to not disturb visual sensory memory and made tones distinct
- infer that participant's performance is same for other two rows as toned row since tone is after
stimulus; therefore multiply by 3 for 3 rows: 3x3 = 9 letters remembered
- Sperling varied interval between presentation of letters and presentation of cue to find duration
of visual sensory memory
- after 1 second, partial report was no better than whole report
Auditory of analog of Sperling's task (Darwin, Turvey, and Crowder (1972))
- auditory presentation over 3 spatially different channels (left, right, middle ear)
- chose visual cue to not disturb auditory sensory memory (bar on screen)
- digits and letters presented 3 to left ear, 3 to right ear, 3 to middle ear
- duration appeared to be 4 seconds
- about 2.5 remembered per trial
Sensory memory by modality
-Iconic memory (visual)
- Duration: less than 1 second
- Capacity: essentially entire visual field
- Echoic memory (auditory)
- Duration: up to 4 seconds
- Capacity: less than iconic memory
- sound stimuli typically do not appear all at once, the way visual stimuli do; they appear in
sequence over time - so it's adaptive for auditory sensory memory to have longer duration but
smaller capacity