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Lecture

PSYC 2520 Lecture Notes - Visual Cortex, Echoic Memory, Iconic Memory


Department
Psychology
Course Code
PSYC 2520
Professor
Hernan Humana

Page:
of 12
Chapter 8: Memory
memory – cognitive process of encoding, storing and retrieving information
encoding – process by which sensory information is converted into a form that
can be used by brain's memory system
storage – process of maintaining information in memory
retrieval – active process of locating and using stored information
literal – physiological changes that occur when something is learned
metaphorical – conceptual information processing models of memory
learning – tendency for behaviour to change as result of experience, with
performance reflects brain's plasticity
three forms of memory: sensory memory, short-term memory, and long-term
memory
sensory memory – memory in which representations of physical features of
stimulus are stored for very brief duration; held long enough to become part of
short-term memory, no analysis takes place but longer than perception
short-term memory – immediate memory for stimuli that have just been
perceived; limited in capacity (7 + or – 2 chunks of information) and duration
(less than 20 seconds)
long-term memorymemory in which information is represented on
permanent or near-permanent basis; durable, no limits
Standing – showed people 10,000 colour slides and found they could
recognize them weeks later
occurs due to physical changes that take place in brain
“modal model” of memory - general conception of memory system
Sensory Memory
not aware – only when presented briefly
have sensory memory for every modality – 2 main: iconic (visual) and echoic
(auditory)
Iconic Memory
iconic memory – sensory memory that holds brief visual image of scene that
has just been perceived; also known as visible persistence
Sperling – presented visual images through tachistoscope at rate of 9 letters on
screen for 50 milliseconds
on average, person could remember 4 or 5 but insisted that for brief time
could see more but images faded to fast to see all
also used partial report procedure to determine whether capacity of iconic
memory accounted for this limitation
asked people to name letters in only one horizontal row indicated by a
tone after letters disappeared
able to repeat letters with perfect accuracy – iconic memory had capacity
for all 9
if delay of tone was longer than 1 second people could onyl relay 50%
could not recall all 9 because had faded from memory
Echoic Memory
echoic memory – sensory memory for sounds that have just been perceived
necessary for comprehending sound, particularly those that constitute speech –
cannot identify word until we have heard whole sound so accoustical information
must be stored temporarliy until all sounds have been received
evidence from partial reporting shows that it lasts less than 4 seconds
Short-Term or Working Memory
Encoding of Information: Interaction with Long-Term Memory
information can enter st memory from sensory of lt memory
working memory – memory for new information and information retrieved from
long-term memory; same as st memory
represents behaviour that takes place inside our head – represents our ability
to remember what we have just perceived and to think about it in terms of
what we already know
Primacy and Recency Effects
free-recall task – remember what you can of information that was just given to
you
primacy effect – tendency to remember initial information due to opportunity
for rehearsal which causes them to be stored in lt memory
recency effect – tendency to remember later information due to fact that they
are last to be rehearsed so are still in st memory
pointed out by Atkinson and Shiffrin
Limits of Working Memory
Llyod and Margaret Peterson – presented people with stimuli composed of 3
consonants: JRG
people recalled info 30 seconds later
when made to count backwards from 3-4 digit numbers consonants were only
accesible for a few seconds and dropped to zero after 15-18 seconds
stimuli remain in st memory for 20 seconds unless rehearsed
Miller – the magical number 7 plus or minu 2: people can retain on average
7+or- 2 pieces of information
chunking – process by which information is simplified by rules, which make it
easily remembered once rules are learned
can remember more if information can be organized into more meaningful
sequence
McNamara and Scott – taught people to chain unrelated words together as
they listened to them – imagined story involving those words
Varieties of Working Memory
Phonological Working Memory:
phonological short-term memory – short term memory for verbal information
(whether presented visually or accoustically)
Conrad – showed how quickly visually presented information becomes encoded
acoustically
briefly showed people lists of 6 letters and then asked them to write letters
saw letters visually but when made errors, they were accoustical (V vs. B)
shows that words were encoded acoustically
phonological memory may be produced by activity in auditory system by circuits
of neurons in auditory association cortex
subvocal articulation – unvoiced speech utterance
although no actual movement may occur, is possible activity occurs in neural
circuits that control speech
when we invision something in our minds It is caused by activity in neurons in
visual association cortex
voice in head is probably from activity of neurons in motor association cortex
Conrad – attempted to determine whether subvocal articulation played role in
phonological working memory
study on deaf children (could not confuse letters because of their sounds)
children who made accoustical errors were ones who were rated as best
speakers by teachers
deaf children who could speak best encoded letters in terms of movements
they would make to pronounce them
clear evidence for articulatory code in working memory
people may use acoustical and articulatory coding – simulatenously say word
and feel themselves say it in head
phonological code stored in lt memory also might help to strengthen rehearsed
information
conduction aphasia is best evidence for existence of phonoligcal st memory
conduction aphasiainability to remember words that are heard, although
they usually can be understood and responded to appropriately; caused by
damage to the connection between Wernicke's and Broca's - deficit in
phonological working memory; might disrupt acoustical st memory by making
such subvocal verbal rehearsal difficult or impossible
Visual Working Memory:
possess working memory that contains visual information either obtained from
immediate environment by means of sense organs or retrieved from lt memory
does not encode all details – find prototype in lt memory
DeGroot – showed chessboards to expert players and to novices and if position
of pieces represented game in progress, experts could glance at board for a few
seconds and then look away and report position of each piece but novices could
not; experts could also recognize immediately if positions were placed
haphazardly
st memories for positions depended on organizational rules stored in lt
memory as result of years of chess playing
Gzowski – found similar pattern in Gretzsky's hockey playing
have ability to manipulate visual information in working memory
Shepard and Metzler – presented people with pairs of drawings that could be
perceived as 3D constructions of cubes and found people could accurately judge
if pairs were same shape even if rotated; were able to do so in head and ones
that were more rotated, took longer to judge
Loss of Information from ST Memory:
st memory information controls behaviour and changes lt memory
can decay but rehearsal refreshes it – but mostly due to displacement
Waugh and Norman – heard lists of 16 digits where last digit was accompanied
by tone and called probe digitwhen people heard it they had to think back to
last occurence of same digit that tell which digit followed that one; distance
between target and probe was 1-12 items
critical variable was number of items, not time that elapsed – shows that new
information displaces old information in st memory