PSY 368 Human
Memory
Sensory Memory
Structural Model
• Memory composed of storage structures that hold memories
for a period of time
• Sensory memory
• Short-term memory (STM)
• Long-term memory (LTM)
Sensory Memory
• Sensory memory
• Very short storage of info from senses
• Functions:
• To allow further processing of the info (STM)
• Helps us to connect our sensory experiences
• Multiple stores:
• Visual sensory memory = iconic memory (Neisser, 1967)
• Auditory sensory memory = echoic memory
• Touch sensory memory = haptic memory
The eye and how it behaves
• At its center is the fovea, a pit
that is most sensitive to light
and is responsible for our sharp
central vision.
• The central retina is conedominated and the peripheral
retina is rod-dominated.
• Limitations of the visual field
• 130 degrees vertically, 180
degrees horizontally
(including peripheral vision)
The eye and how it behaves
• Eye Movements serve two major functions
• Saccades to Fixations – Position target objects of interest on the
fovea
• Duration 10ms - 120ms
• Very fast (up to 700 degrees/second)
• No visual perception during saccades
• Tracking – Keep fixated objects on the fovea despite movements
of the object or head
• eye movement video
• Eye Fixations perceptions are gathered during fixations
• 90% of the time the eye is fixated
• duration: 150ms - 600ms
Video examples:
1|2|3|4
Iconic Memory
• Questions:
• What happens to the visual image?
• How do we get information out of
the image?
• How do we connect visual images
(from different fixations)?
• One answer: have a memory storage
separate from the visual image
itself
Video example
Iconic Memory
• Is there scientific evidence for iconic memory?
• The number of items that can be accurately perceived at a glance
• The number of objects that can be attended to at once
• Problem: If the info decays quickly, subjects don’t
have enough time to report it.
Iconic Sensory Store
If I show you this….
your iconic memory does this…
…but
faster!
• Reports of “seeing” a scene after it disappeared
• This introspective description was suggestive of some kind of
"single, visible, precategorical, high-capacity, quickly-decaying memory
that holds incoming visual stimulation for further processing" (Loftus
& Irwin, 1998).
Iconic Memory
George Sperling (1960)
• Believed that he can see more than he can
report
•
The limitation is not in storing the information but
in reporting it
• Solved this problem (span limit problem) and supported
the existence of iconic memory
• Used two techniques:
• whole report
• partial report
Iconic Memory
50 msec
Whole Report:
•
Presented a 4 x 3 matrix of letters and
digits for 50 ms, and asked subjects to
report all the items they saw.
Report Cue
ready
+
A
N
P
L
K
M
D
T
W
B
S
R
Iconic Memory
Whole Report:
•
Subjects are shown an array of items and asked to report all the
items they saw.
A
N
P
L
K
M
D
T
W
B
S
R
so 9/12 would be = 75% accuracy
Results:
• Subjects could not report more
than about 4.5 items on each
trial. (4.5/12 = 38%)
• held true over wide range of
exposure durations (.015 - .5
sec)
Iconic Memory
50 msec
Partial Report:
•
4 x 3 matrix of letters for 50 ms, subjects
report all the items from one particular row.
•
He cued them which row to report by
playing a high, medium, or low tone.
Report Cue
(I have horn, drum, pong)
S
B
U
C
M
Y
D
F
L
K
W
D
S
B
U
C
M
Y
D
F
L
K
W
D
S
B
U
C
M
Y
D
F
L
K
W
D
ready
+
B
M
C
K
N
V
P
A
W
J
U
L
Iconic Memory
Partial Report:
• Subjects are shown an array of items and asked to report a subset of
the items they saw.
B
M
C
K
N
V
P
A
W
J
U
L
So 3/4 = 75% accuracy
Results:
• Subjects could typically
report all 4 items on each
trial. (4/4= 100%)
Iconic Memory
• So far we’ve addressed capacity of iconic memory, what about
duration, how long does it last?
• Effect of delay of tone
Report
• Varied time between the disappearance
of theCue
display and the onset of the cue tone: 0 to 1 sec
Iconic Memory
Results:
• With short delays, can
report proportionately
more, but with longer
delays partial report
performance is similar to
whole report
Report Cue
Iconic Memory
• Conclusions from Sperling (1960):
• Evidence of iconic memory
• Properties:
• High capacity of information
• Very short duration (lasts about.5 sec)
• Pre-categoical (“raw,” unprocessed) information (we’ll
return to this)
Iconic Memory
• Memory vs. afterimage of the eye?
A little on color vision
Wavelength
Input
Cones
“Blue”
“Green”
Signal to Brain
Blue
Equal Parts Red
and Green =
Yellow
“Red”
• Trichromatic theory of
color vision
A little on color vision
• Trichromatic theory of
color vision
• Opponent Process
Theory
• Red opposes Green
• (Red + Green) opposes Blue
•
Explains color afterimages
Iconic Memory
report
cue
Banks and Barber (1977)
• Similar to Sperling
methodology
• If using a retinal after-image
then letters with
complimentary colours would
be reported
• Red becomes Green
• Yellow becomes Blue
Results:
- their data showed subjects can
recall correctly with a color cue
KJF
SBN
EWP
50 msec
presentation
short
interval
(250 msec)
red
Iconic Memory
• Is the information in iconic memory
“unprocessed?”
• Pre-categorical report: based on sensory
properties (location/color)
• Post-categorical report: based on categorical
properties (type of item - letters or digits)
• Von Wright (1972)
• Merikle (1980)
Iconic Memory
Von Wright (1972)
Used partial report method
with different report
criteria
• type (numbers vs letters)
• color
• location
Partial Report Advantage
Is info in iconic memory pre-categorical?
4
3.5
3
2.5
2
1.5
1
0.5
0
Type
Color
Location
before
display
+5 ms
+500 ms
Cue Time
Iconic Memory
• BUT Merikle (1980)
used different kinds of
displays (perceptual
groupings, letters, and
numbers) and found that
the partial report
advantage for type
(number vs letter) as
strong as location
• So it’s possible info
processed to some degree
Problems with Iconic Memory
1. Information may not be precategorical
• e.g., Merikle (1980)
2. The idea of output interference rather than decay.
• Dick (1971) found that the first item was reported correctly
equally often for whole and partial reports.
• The act of recalling one item can interfere with recall of the next item, so the more items
you're required to report, the less likely you are to report the last one successfully
3. The types of errors that the subjects make.
• Auditory confusion errors (e.g. if letter is B, subjects more likely to
report V than R)
• Mewhort & Leppman (1985) – identification (‘T’ was there or not)
error rates didn’t increase with duration between display and probe
Sensory Memory
4. An important distinction:
• Stimulus persistence: Something that looks or sounds like the stimulus
continues to be present for a short amount of time after the stimulus is
no longer present
• Information persistence: Information can be extracted from a stimulus for
a short amount of time after the stimulus is no longer present
Early view: stimulus persistence and information persistence were basically
the same thing.
But more recent research suggests that:
• Stimulus persistence reflects residual neural activity after exposure to a stimulus
• Information persistence reflects the same type of memory that is used for
longer-lasting information
Echoic Memory
• Sensory memory for auditory information
• Not as much research done on echoic memory as
iconic
The ear and how it behaves
Changes in Air Pressure
• Stimulus is much more
linear and transitory
Echoic Memory
• Darwin, Turvey, and Crowder (1972)
• Whole report: report all 3 lists
• For partial report, the cue was:
- light on the left = report left speaker list
- light on the right = report right speaker
list
- light in the center = report list that was
• The interval from list offset to cue
onset was:
- 0 seconds, 1 second, or 4 seconds
Echoic Memory
• Darwin, Turvey, and Crowder (1972)
• Findings:
• Partial report advantage up
until about 4 sec
• so echoic memory lasts 4 s or
more
• Echoic memory holds less
than iconic memory
Echoic Memory
• Some of the Effects discovered in study of
echoic memory
• Using Immediate Serial Recall tasks
• Presented a list of items and asked to recall them
in the order in which they were presented
• Recency effect
• Modality effect
• Suffix effect
•
Note: while these effects were discovered in the study of echoic
memory, they are currently believed to reflect general memory
principles rather than exclusively features of echoic memory
Echoic Memory
• Recency effect - last item of list better remembered
than items earlier in the list
Echoic Memory
• Suffix effect - recency effect disappears if an auditory
Typical Suffix Effect experiment has 2
item follows last list item
conditions:
Suffix Effect - Crowder (1972)
• Control condition list of auditory
items presented.
Percentage Correct
100
• Suffix condition the same, except that
each list is followed by a spoken word.
80
60
No Suffix
0 Suffix
40
20
• Why the effect?
0
1
2
3
4
5
6
List Position
7
8
9
•
Interference from last item disrupts
memory trace
Echoic Memory
• Modality effect - last item of list better remembered
when presented aloud than visually or silently
Why?
Acoustic information persistence
lasts approx. 2 seconds -- unless a
subsequent similar stimulus interferes
with it.
When the subject reports the last
item, it is still present in echoic
memory.
In contrast, visual stimulus
persistence doesn't last that long.
Sensory Memory
Summary
(1) Capacity - limited only by amount of info that
can be received by the perceptual system (e.g.,
eye, ear)
(2) Duration of memory:
- iconic - up to about 1 sec
- echoic - about 4 - 20 sec depending on type of
info
(3) Type of info - mostly pre-processed, but
some processing may occur after 250 - 300 ms