Cognitive Processes
PSY 334
Chapter 3 – Attention
What is Attention?
 Attention is the allocation of limited
processing resources.
 Visual features such as shape, color,
texture, motion are processed in parallel.
 Serial bottleneck – occurs when it is no
longer possible to process in parallel.
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When does it occur – early vs late
selection
How do we select what to attend to?
Visible Bottleneck Task
 http://opl.apa.org/contributions/Pashler/prp.html
 This task illustrates how difficult it is to
pay attention to two things at the same
time.

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Both tasks require a choice of response
and the same cognitive resource cannot be
devoted to both tasks at the same time.
The competition goes away when one task
does not involve a choice (e.g., press any
button when you hear a tone).
How we Experience Attention
 Stream of consciousness -- we learn and
remember what we attend to.
 Paying attention results in a feeling of
mental effort.
 Can be directed internally but also pulled
(attracted) by external events.
 Varies with arousal and fatigue.
 Studied by looking at response
competition.
Auditory Attention
 The response competition comes from
having two ears.
 Dichotic listening task – uses
“shadowing.”
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
Two different messages are presented,
one to each ear. Subjects are asked to
speak what they hear.
People can attend to only one message at
a time.
Auditory Shadowing
Broadbent’s Filter Theory
 People do not remember the content of
the unattended ear.

Voice or noise, sex, but little else.
 Broadbent’s filter theory proposed that
filtering occurs early in processing based
on physical characteristics (pitch, ear).

Neural evidence supports the ability to
select one ear to listen to.
 Cocktail party effect – attention switches
based on content of unattended ear.
Broadbent’s Early Selection
Only the selected information
gets through.
Gray & Weddeburn’s Study
Subjects can successfully shadow
a message that jumps back and
forth between ears.
This means that people can
shadow based on meaning, not
just physical characteristics.
Treisman’s Attenuation Theory
 Treisman’s attenuation theory – subjects
deemphasize but not filter out the
unattended message.

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Meaning switched from one ear to the
other.
Some subjects switch ears even when told
not to, following the semantic content.
 Semantic criteria apply to all messages,
filtered or not.
Treisman’s Attentuation
Theory
All information passes
through but some is weaker
(attenuated).
Late Selection Theory
 Deutsch & Deutsch’s late selection
theory – the limitation is in the response
system, not the perception.


Both messages are perceived in terms of
meaning, but only one can be shadowed at
a time.
The criterion for selecting what to say can
change – based on ear or meaning.
Late Selection Theory
Decide what to
say
Shadow by
meaning
Shadow by ear
Testing the Theories
 Dichotic listening task:

Shadow one message but listen for a
target word in both ears (tap when heard).
 Late selection theory predicts no
difficulty hearing the target in either ear.
 Attenuation theory predicts less
detection in non-shadowed ear.


87% detection in shadowed ear
8% detection in non-shadowed ear
Neural Evidence (Auditory)
 An enhanced response occurs in the
primary auditory cortex but not earlier in
the auditory pathways.

Both EEG (using ERP) and PET show this.
 The enhancement occurs quickly,
sooner than meaning can be interpreted.
 Effects are signal attenuation and
enhancement, not complete filtering out.
Visual Attention
 We can choose where to fixate our eyes
for greatest visual acuity.

Other portions of the visual field are
attenuated.
 Visual attention need not be located
where the eyes are fixed.
 Posner – subjects can attend to objects
up to 24 degrees from the fovea.

Shift of attention precedes eye movement.
Selective Attention
Spotlight Metaphor
 Spotlight can be broad or narrow
(degrees of visual angle).

Broad areas processed less well.
 A narrow focal point gives optimal
processing but it takes time to move the
focus to other areas of the visual field.
 We move our eyes around a complex
visual stimulus.

Neisser & Becklen’s shadowing task.
Neural Evidence (Visual)
 Attention consists of enhanced neural
response in a particular spatial location
in the visual cortex.

By increasing neural activity in a particular
location, input to that location can be
processed faster.
 Specific details are “higher order”
properties and take longer to recognize.
 Enhancement comes from V4 not V1.
Neural Evidence
Activity occurs on the
opposite side from the
stimulus.
Monkeys showed greater
activity while waiting (b)
when the original stimulus
was on the saccade path.
Visual Search
 Feature-based serial search – Neisser

Find the letter K in a string of letters.
 Pop-out – locate a distinctive feature in
an array without searching each item.
 Treisman & Gelade – locating a
conjunction of features takes longer than
locating a single, distinctive feature.

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T among I’s & Y’s
T among I’s & Z’s
400 ms
800 ms
Visual Pop-Out
Can you find the owl?
From Delphine Chedru Spot
It! Find the Hidden Creatures.
Can you find the bee?
Which is harder to see?
Why?
Treisman & Gelade’s Data
The Binding Problem
 If different neurons process different
features of an object (color, motion,
lines) how are such features combined?
 Feature integration theory (Treisman) –
people must focus attention in order to
synthesize features into a pattern.
 Illusory conjunctions – mistakes in
binding when attention is disrupted.

See pink T, yellow S, blue N but report
seeing a pink S that was never presented.
Attention Enhances Features
 Attentional enhancement can be based
on specific features not simply the
contents of a visual field.

Blue and green bars (macaques) – cell
firing is suppressed if green is attended.
 Black and white teams and black gorilla:
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8% of those attending the white team saw
the black gorilla
67% of those attending the black team saw
the black gorilla (both were black)
http://viscog.beckman.illinois.edu/flashmovie/23.php
Selective Cell Firing
Blue is attended
Cell fires despite presence of green
Green is attended
Cell firing is greatly reduced
despite presence of blue
Visual Neglect
 Visual neglect may occur due to damage
to:
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posterior parietal lobe
pulvinar (thalamus)
superior colliculus (eye-tracking)
 People with injuries to the parietal lobe
have difficulty shifting attention from one
side of the visual field to the other.
Attention Deficit
Right parietal lobe
damage prevents
subjects from shifting
their attention to the other
visual field.
The first neglect
patient (a) has
copied the right
sides of both
figures, ignoring
the left.
The second patient
(b, c) neglects the
left sides when
copying but draws
a more complete
figure from
memory.
Halligan et al, 2003
Kinds of Deficits
 Damage to the right parietal lobe
produces deficits in cued attention tasks:

No problem with items on the right but
inability to shift to items on the left.
 Unilateral neglect – with severe damage
people totally ignore the left visual field.
 Left parietal damage inhibits attention to
details.
 Deficits occur across modalities
Object-Based Attention
 Attention can be focused on particular
objects, not just regions of space.

Sometimes it is easier to attend to an
object (bumps on stimuli).
 Inhibition of return – if we have already
looked at a location it is harder to return
to it.

Flickering squares take longer to identify
because already viewed, even when
rotated.
Two Attention Tasks
Two Theories
Spotlight theory – we move
our attention to parts of the
visual field.
Object-based theory – we move
our attention to objects.
Object-Based Neglect
 Just as objects can be attended to
independent of their location, neglect
can apply to objects, not locations.
 Some patients neglect one side of
objects regardless of which visual field
they occur in.
A Central Bottleneck
 We can only process one thing at a time
within a single modality (vision, hearing).
 Central cognition may be the most
important bottleneck – the central
bottleneck.
 Whether two tasks can be done at once
depends on whether they compete for
the same resources.

Schumacher dual-task experiment.
Dual Task Processing
Automaticity
 Practice reduces the need for attention
by reducing central cognition, making a
task automatic.

Practice enables parallel processing.
 Spelke’s two tasks:
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Read text for comprehension
Write down words read by an experimenter
After 6 weeks subjects could read at
normal speed and answer questions.
Stroop Effect
 Color words were presented printed in
different ink colors.

Control stimuli were non-color words in
different inks or color bars (not words)
 Subjects were asked to name the ink
color as quickly as possible.
 Demo
Stroop Demo
Why it Happens
 Automatic processes are difficult to stop.
 It is nearly impossible to look at a word
without reading it.
 Neutral words name non-colors so ink
can be named without interference.
 Color words that conflict with ink color
take longer because reading the word
cannot be inhibited.
Practice With Stroop Tasks
 What happens if you compare tasks that
are not well-practiced?
 MacCleod & Dunbar asked subjects to
associate color names with shapes.
MacCleod & Dunbar’s
Conditions
 Congruent – random shape was in the
same ink color as its name.
 Control –
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white shapes were presented and subjects
said the name of the color for that shape
colored shapes were presented and
subjects named the ink color of the shape
 Conflict – the random shape was in a
different ink color than its name.
Results
 At first, color naming was more
automatic than shape naming and was
unaffected by congruence with shape.
 After 20 days practice, shape naming
was affected by congruence with ink
color
 Practice reversed the Stroop effect and
made shape naming like color naming.
Executive Control
 Control of attention occurs in the parietal
lobes, but central cognition occurs in the
prefrontal cortex.
 Damage to the prefrontal cortex impairs
executive control.

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Response is stimulus-driven not intentional
Cannot do the Stroop task because
automatic processing takes over
 Arbitrates between competing processes