Cognition
transforming perceptions into
action and thought
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Perception
and Cognition
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Attention
Memory
Language
Cognitive Modules
Consciousness
Animal Cognition
Cognitive Science
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Attention
selection, processing, and
consciousness of specific
sensations
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Attention
• recognized as very important to perception
– how much can we do at once? why?
• difficult to describe in objective terms
– clarity of perception; intensity; consciousness
• recent work: emphasis on selection
• selective access:
– only certain parts of [visual] input sent on for
further processing
– examples: selective looking and selective listening
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Example 1:
Selective Looking (Neisser; Simons)
• Watch two teams of players
– one in white shirts
– one in black shirts
• Each player throws basketball to others on their
team --- teams do not interact
• Select one of the colours (white or black)
– Task: count number of times ball is exchanged
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Neisser; Simons
• Pick the white or black team
• Count the number of times their basketball is
exchanged
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
From http://www.wjh.harvard.edu/~viscog/grafs/demos/gorilla.shtml
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Neisser; Simons
• Result:
– over half the observers do not see the person in the
gorilla suit
• inattentional blindness:
– if we don’t attend to something we won’t see it
• Instead of a complete, detailed world, we only
see a small part of it
– the part we are attending to!
• This is how magicians make things (dis)appear
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Card Trick
• Pick a card
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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I’ve removed your card
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Selective Looking and
Inattentional Blindness
• Does anything get through?
– picture of a smiley face (but not a sad one)
– name of observer (Sara, George)
but not close names (Sura, Geosge)
– highly familiar stimuli
– highly predictable or expected stimuli
• Some things “draw attention” to themselves
– processed “without attention”, or
very easily pass “perceptual filters”
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Example 2:
Selective Listening
(Cherry and many others)
• Two audio streams: one input per ear
repeat (“shadow”) what is being said
each audio stream is independent of each other
(streams don’t interact)
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Cherry
• Select one of the streams (left or right)
repeat (“shadow”) what is being said
fruit,
brain, morning,
paper, light,
planet,
brain
fruit
paper
morning
light
planet
aircraft
door
shirt
...
swan
...
Shadowing left
right ear
ear
after the listener has finished shadowing,
test what they remember from other stream…
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Cherry
• Result
– Listeners acquire almost nothing from unattended
stream
• Inattentional deafness:
– if we don’t attend to something, we won’t hear it
• Instead of a complete, detailed world, we only
hear a small part of it
– yes dear, of course dear, you’re so right dear
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Selective Listening and
Inattentional Deafness
• Does anything get through from unattended
channel?
– large change in volume
– change in gender of speaker
– not a change in language
• Again, some things” draw attention” to themselves
– processed “without attention”
• Related:
– “cocktail-party problem” -- multiple speakers
– “could you repeat that?” -- short term auditory memory
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Example 3:
Selective Access (Posner)
• Focus visual attention to an area by using a cue
– “Spotlight” or “zoom lens”
• measure time to identify target item when:
– observer does not know where item will appear
– observer does know where item will appear
• cue is a briefly presented dot at the location of
target
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Posner: Example 1
• no cuing: what letter appears?
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Posner: Example 1
• no cuing: what letter appears?
2002/03/05
A
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Posner: Example 2
• with cuing: what letter appears?
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Psyc202-005, Copyright Jason Harrison 2002
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Posner: Example 2
• with cuing: what letter appears?
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Psyc202-005, Copyright Jason Harrison 2002
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Posner: Example 2
• with cuing: what letter appears?
2002/03/05
N
Psyc202-005, Copyright Jason Harrison 2002
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Results: Cue versus No Cue
Cue reduces time
Time
No Cue
Cue
Advance knowledge of location improves performance
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Results: Relative position of Cue
Greatest reduction
at location of cue
Reduction
of time
Cued location
Amount of reduction depends on distance from cue
-attention is like a spotlight or a zoom lens
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Cue triggers “formation of a spotlight”
• whatever is in spotlight is attended
• more it is attended, the better it is processed
• size, shape of spotlight can be controlled
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Different types of cues
a) exogenous (outside generating)
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low-level “reflexes”
sudden changes (e.g., flash or movement)
draws attention automatically
b) endogenous (inside generating)
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2002/03/05
high-level control
instruction (via some kind of visual sign or
pattern)
sends attention to requested location
Psyc202-005, Copyright Jason Harrison 2002
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Exogenous Cuing
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Exogenous Cuing
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Exogenous Cuing
N
No interpretation needed - cue is at target location
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Endogenous Cuing
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Endogenous Cuing
Observer need to interpret the cue
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Endogenous Cuing
C
Observer need to interpret the cue
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Effect of Cues
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Both types of cues control the same
attentional mechanism (spotlight) but reflect
different strategies
a) exogenous (low-level control)
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bottom-up control of attention
based on what’s actually happening in
environment
b) endogenous (high-level control)
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2002/03/05
top-down control of attention
based on what observer believes
Psyc202-005, Copyright Jason Harrison 2002
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Summary of Selection
• Selective Looking
– inattentional blindness
• Selective Listening
– inattentional deafness
• Selective Access
– cuing, exogenous, endogenous
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Attention: Selective Processing
• Selection of sensations (left ear, right ear)
• Selective access
• Selective construction
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Selective Access
• Only certain parts of [visual] input sent on for
further processing
– some parts ignored, some filtered, some selected
• Perception:
coordinated interaction of different perceptual
systems
• Even if attention allows observer to see,
how well are things put together?
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Selective Construction
• Only certain parts of [visual] input are put
together
• Attention both allows conscious vision and
builds up visual representations
• Severe limits to what can be accessed or
constructed…
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Example 1: Visual Search
- what visual properties are formed immediately?
- diagnostic: visual search
2002/03/05
- e.g., is there a blue dot?
Psyc202-005, Copyright Jason Harrison 2002
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Example 1: Visual Search
-Result: for some targets, search always fast
2002/03/05
- target “pops out” of display
- e.g., is there a blue dot?
Search slope = 0
(“pop-out”)
Psyc202-005, Copyright Jason Harrison 2002
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Example 1: Visual Search
-Explanation:
- for some properties, a unique value will
draw attention (exogenous cue)
- e.g., where’s the blue dot?
-e.g., a single large item among small ones
-e.g., a single curved item among straight ones
Search slope = 0
Proposed application: data (“pop-out”)
visualization
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Example 1: Visual Search
-However, this is not always the case
2002/03/05
- e.g., is there a blue vertical line?
Psyc202-005, Copyright Jason Harrison 2002
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Example 1: Visual Search
-Result: for some targets, search is slow
2002/03/05
- effort needed
- e.g., is there a blue vertical line?
600
Reaction
time (ms)
500
400
search slope
(30-100 ms/item)
300
Number of items (set size)
Psyc202-005, Copyright Jason Harrison 2002
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Example 1: Visual Search
Explanation
2002/03/05
- need to combine properties to detect target
-combination is not automatic
-spotlight of attention is needed to “weld”
properties together
-search is a serial process - time needed
depends on number of items
-spotlight travels at about 50 ms/item
Psyc202-005, Copyright Jason Harrison 2002
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Example 2: Perception of Scenes
Recall:
-visual input via high-resolution fovea
180°
Ret ina
Fov e a
4°
Ey e
- highe st
densit y
of cones
Retina has good acuity only in central 4° of vision
-”clear vision” only in this range
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Example 2: Perception of Scenes
When perceiving a scene, can only get “pieces” of it
at any instant
2002/03/05
-need to move eyes around to see scene
Psyc202-005, Copyright Jason Harrison 2002
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Saccades
Need to move eyes around to see the world
- eye movements make jumps called saccades
Saccades made about 3 times / second
- jump to various parts of the world
-eyes are almost always moving
(unless something really interesting is seen)
-by moving eyes around,
a complete scan of world is made
Construction of whole from
saccades
Question: How do the “pieces” (individual fixations)
get put together?
Possible answer: The information from each fixation
is collected into a visual buffer
somewhere in the brain
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Visual Buffer
Accumulates information
(eyes being moved around)
Visual Buffer
Accumulates information
However, no evidence of this has ever been found
Visual Buffer: Does not exist
• If it did, it should be easy to see any changes
made to the image
Seeing changes
• sometimes very difficult to do…
• insert brief blank interval between original and
changed images
– eye blink
– saccade or eye movement
– occlusion
– movie scene cut
– see examples at
http://www.wjh.harvard.edu/~viscog/lab/demos.html
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Seeing changes in real-life
• Observers have great difficultly seeing a
change made during an interruption
– Change Blindness
• This can happen in real life
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
http://www.wjh.harvard.edu/~viscog/grafs/demos/door.shtml
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
56
Explanation of Change Blindness
• Attention is needed to see change
– without it, observers are “change blind”
• Attention combines pieces of the image
– forms them into a coherent representation: token
– tokens support perception (detection) of change
– tokens describe actual objects in world
(basis for action, e.g., grasping)
– tokens can be “mis-mapped” across an interruption
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Notes on Change Blindness
1. In everyday life, we usually see change
-if something changes, creates a motion signal
-motion is an exogenous cue; draws attention
-if something interferes with drawing of attention
(flicker, occlusion) then attention doesn’t go to
change
-> won’t see it
2002/03/05
-attentional distraction is a major cause of
traffic accidents (e.g., cell phone usage)
Psyc202-005, Copyright Jason Harrison 2002
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Notes on Change Blindness
2. There is no accumulation of built-up representation
2002/03/05
-if observer looks at picture for several seconds
before flicker sequence begins -> no effect
- representation built up by attention (token) stays
built up only as long as attention stays on it
-token “dissolves” after attention withdrawn
-token “remapped” after flicker/blind/saccade
Attention acts like a hand:
-token exists as long as pieces of input are “held”
-if hand picks up drops and later picks up
something else, token “remapped” to new item
Psyc202-005, Copyright Jason Harrison 2002
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Notes on Change Blindness
3. If we only see a few objects at a time,
why do we have the impression of seeing lots?
-representation of object formed on demand
-whenever it is needed, it is built
-virtual representation -> “just in time” system
-example: refrigerator light
-only on when needed -> looks like it’s always on
-example: object representation
-only there when needed
-> looks like it’s always there
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Summary of Attention
• Selection is key:
– selection of stimuli: looking, listening
– processing of stimuli: access, construction
• Blindness comes in many forms
– inattentional blindness
– change blindness
• Tasks:
– counting passes of ball, shadowing words, letter
recognition, visual search, changes across blinks,
flashes and interruptions.
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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You might be wondering
• Where in my head does this all happen?
• How do we know about these locations?
• Time for
Neural Sites of Visual Attention!
2002/03/05
Michael Posner
Psyc202-005, Copyright Jason Harrison 2002
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Neural Sites of Visual Attention
• Studied via
– human brain lesions (strokes, traumas)
– brain scans of humans
– cell recordings in monkeys
• Two different networks (Posner)
– Posterior: expression of attention
– Anterior: control of attention
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Posterior Network
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parietal lobe (and south)
movement and engagement of attention
unconscious processing
three interacting systems:
– disengagement
– movement
– engagement
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Posterior Systems
• disengagement
– posterior parietal lobe
– permits processing of attended source to end
• movement
– superior colliculus
• eye movements: location map for tectopulvinar system
– allows attention to be drawn to new location
• engagement
– thalamus (pulvinar)
– blocks input from unattended sources
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Anterior Network
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control of attention
provides contents of awareness
conscious processing
network includes:
– anterior cingulare cortex (prefrontal)
– frontal eye fields
• handles executive control
– voluntary shifts of attention
– responses to endogenous cues
• location of free will?
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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Summary of Neural Sites
• Posterior
– automatic movement and engagement of attention
• Anterior
– voluntary shifts of attention
2002/03/05
Psyc202-005, Copyright Jason Harrison 2002
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