Chapter 4

Chapter 4
Some Questions to Consider
• Is it possible to focus attention on just one
thing, even when lots of other things are
going on at the same time?
Under what conditions can we pay attention
to more than one thing at a time?
What does attention research tell us about
the effect of talking on cell phones while
driving a car?
Is it true that we are not paying attention to a
large fraction of the things happening in our
• Process of concentrating on specific features
of the environment or on certain thoughts or
– Selective: excluding of other features of the
– Limited: in capacity and timing
– Both overt and covert: we can consciously attend
to information but some information grabs our
Selective Attention
• Ability to focus on one message and ignore
all others
We do not attend to a large fraction of the
information in the environment
Filtering out some information and promoting
other information for further processing
Research Method: Dichotic Listening
• One message is presented to the left ear and
another to the right ear
Participant “shadows” one message to
ensure he is attending to that message
Can we completely filter out the message to
the unattended ear and attend only to the
shadowed message?
Caption: In the shadowing procedure, a person repeats out loud
words he has just heard.
Results of Dichotic Listening
• Participants could not report the content of
the message in unattended ear
– Knew that there was a message
– Knew the gender of the speaker
• However unattended ear is being processed
at some level
– Cocktail party effect
– Change in gender is noticed
– Change to a tone is noticed
Models of Selective Attention
• Where does the attention filter occur?
– Early in processing
– Later in processing
• Early selection model
– Broadbent’s filter model
• Intermediate selection model
– Tresiman’s attenuation theory
• Late selection model
– e.g. McKay (1973)
Broadbent’s Filter Model
• Early-selection model
– Filters message before incoming information is
analyzed for meaning
Caption: Flow diagram of Broadbent’s filter model of
Broadbent’s Filter Model
• Sensory memory
– Holds all incoming information for a fraction of a
– Transfers all information to next stage
Broadbent’s Filter Model
• Filter
– Identifies attended message based on physical
– Only attended message is passed on to the next
• Detector
– Processes all information to determine higherlevel characteristics of the message
Broadbent’s Filter Model
• Short-term
– Receives output of detector
– Holds information for 10-15 seconds and may
transfer it to long-term memory
Broadbent’s Model Could Not Explain
• Participant’s name gets through
– Cocktail party phenomenon
• Participants can shadow meaningful
messages that switch from one ear to another
– Dear Aunt Jane (Gray & Weddeburn, 1960)
• Effects of practice on detecting information in
unattended ear
– You can be trained to detect in unattended ear
– Based on the meaning of the message
Tresiman’s Attenuation Theory
• Intermediate-selection model
– Attended message can be separated from
unattended message early in the informationprocessing system
– Selection can also occur later
Caption: Flow diagram for Treisman’s attenuation model of selective
Treisman’s Attenuation Theory
• Attenuator
– Analyzes incoming message in terms of physical
characteristics, language, and meaning
• Attended to message is let through the
attenuator at full strength
Unattended message is let through at a much
weaker strength
Treisman’s Attenuation Theory
• Dictionary unit
– Contains words, each of which have thresholds for
being activated
Words that are common or important have low
Uncommon words have high thresholds
Caption: The dictionary unit of Treisman’s model contains words, each of
which has a threshold for being detected. This graph shows the thresholds
that might exist for three words. The person’s name has a low threshold, so it
will be easily detected. The thresholds for the words rutabaga and boat are
higher, because they are used less or are less important to this particular
Late Selection Models
• Selection of stimuli for final processing does
not occur until after information has been
analyzed for meaning
Late Selection Models
• McKay (1973)
– In attending ear, participants heard ambiguous
“They were throwing stones at the bank.”
– In unattended ear, participants heard either
Late Selection Models
• McKay (1973)
– In test, participants had to choose which was
closest to the meaning of attended to message:
They threw stones toward the side of the river
They threw stones at the savings and loan association
Late Selection Models
• McKay (1973)
– The meaning of the biasing word affected
participants’ choice
– Participants were unaware of the presentation of
the biasing words
Task Load and Selective Attention?
• Task load: how much of a person’s cognitive
resources are used to accomplish a task
– High-load: uses almost all; no resources for other
– Low-load: uses few; resources for other tasks
Caption: Flanker-compatibility task. (a) Display in which the small square is the target,
and the large square on the right is the distractor. This distractor is “compatible”
because it is the same as the target. (b) Display in which the distractor is “incompatible”
because it is different from the target. (c) Results of Green and Bevelier’s (2003)
experiment, which found that the reaction time to indicate the presence of a target is
longer for the incompatible distractor (bar I) than for the compatible distractor (bar C).
Flanker-Compatibility Task
• Can participants focus their attention on
detecting the target so that the identity of the
distractor will not affect their performance?
Flanker-Compatibility Task
• Low-load condition: one potential target
– Reaction time is longer for incompatible distractors
– Participant still had resources available to process
additional information
Caption: Stimuli for the flanker-compatibility task in which the load is
increased by adding additional stimuli to the display. The target is still the
square, as in figure 4.10, so the distractor is compatible in (a) and
incompatible in (b). The results, shown in (c), indicate that under this highload condition, the reaction times are the same for both compatible and
incompatible distractors. (From Green & Bevelier, 2003).
Flanker-Compatibility Task
• High-load condition: type of distractor does
not affect reaction time
– Participants use all resources
– No resources to process the distractor
Video-Game Experts
• Low load: experts’ performance is similar to
High load: experts still had enough resources
left to process distractors
– Performance transferable to flanker-compatibility
Effect of Load on Selective Attention
• High-load experiments support early selection
• Low-load experiments support late selection
Divided Attention
• Practice enables people to simultaneously do
two things that were difficult at first
– Spelke et al. (1976)
After hours of practice, participants could read and
categorize dictated words
Divided Attention
• Schneider and Shiffrin (1977)
– Divide attention between remembering target and
monitoring rapidly presented stimuli
Memory set: 1-4 target characters
Test frames: could contain random dot patterns, a
target, distractors
Caption: Consistent mapping condition for Schneider and Shiffrin’s
(1977) experiment.
Caption: Improvement in performance with practice in Schneider and
Schiffrin’s (1977) experiment. The arrow indicates the point at which
participants reported that the task had become automatic. This is the
result of experiments in which there were four target stimuli in the memory
set and two stimuli in each frame.
Divided Attention
• Consistent mapping condition: target would
be numbers, and distractors would be letters
• Over time, participants became able to divide
their attention
• Automatic processing occurs without intention
and only uses some of a person’s cognitive
Divided Attention
• Stroop effect
– Name of the word interferes with the ability to
name the ink color
– Cannot avoid paying attention to the meanings of
the words
Caption: Varied mapping condition for Schneider and Shiffrin’s (1977) experiment. This
is more difficult than the consistent mapping condition because all the characters are
letters and also because a character that was a distractor on one trial (like the T) can
become a target on another trial, and a character that was in the memory set on one
trial (like the P) can become a distractor on another trial.
Divided Attention
• Schneider and Shiffrin (1977)
– Varied mapping condition: rules changed from trial
to trail
– Over time, participants never achieved automatic
Divided Attention
• Controlled processing: participants paid close
attention, and their search was slow and
Caption: Comparing performance on the consistent and varied mapping tasks. Note
that the horizontal axis indicates the duration of each target frame. These graphs
show that frames must be presented for longer durations to achieve good
performance in the varied mapping condition.
Divided Attention
• 100-car naturalistic driving study
– Video recorders placed in cars
– Risk of accident is four times higher when using a
cell phone
Divided Attention
• Strayer and Johnston (2001)
– Simulated driving task
– Participants on cell phone missed twice as many
red lights and took longer to apply the brakes
Same result using “hands-free” cell phone
Attention and Visual Perception
• Inattentional blindness: a stimulus that is not
attended is not perceived, even though a
person might be looking directly at it
Caption: Inattentional blindness experiment. (a) On each trial, participants
judge whether the horizontal or vertical arm is longer. (b) After a few trials,
the inattention trial occurs, in which a geometric object is flashed along
with the arms. (c) In the recognition test, the participant is asked to
indicate which geometric object was presented.
Attention and Visual Perception
• Change blindness: if shown two versions of a
picture, differences between them are not
immediately apparent
– Task to identify differences requires
concentrated attention and search
Caption: Frames from the video shown in the Levin and Simons’ (1997)
experiment. Note that the woman on the right is wearing a scarf around her
neck in shots A, C, and D, but not in shot B. Also, the color of the plates
changes from red in the first three frames to white in frame D, and the hand
position of the woman on the left changes between shots C and D.
Overt Attention
• Eye movements, attention, and perception
– Saccades: rapid movements of the eyes from one
place to another
– Fixations: short pauses on points of interest
– Studied by using an eye tracker
Bottom-up Determinants of Eye Movement
• Stimulus salience: areas that stand out and
capture attention
– Bottom-up process
– Depends on characteristics of the stimulus
– Color and motion are highly salient
Top-Down Determinants of Eye Movements
• Scene schema: knowledge about what is
contained in typical scenes
– Help guide fixations from one area of a scene to
• Eyes movements are determined by task
– Eyes movements preceded motor actions by a
fraction of a second
Caption: Sequence of fixations of a person making a peanut butter
sandwich. The first fixation is on the loaf of bread.
Covert Attention:
Attention without Eye Movements
• Precueing: directing attention without moving
the eyes
– Participants respond faster to a light at an
expected location than at an unexpected location
– Even when eyes kept fixed
Caption: Procedure for (a) valid trials and (b) invalid trials in Posner et
al.’s (1978) precueing experiment; (c) the results of the experiment.
The average reaction time was 245 ms for valid trials but 305 ms
for invalid trials.
Object-Based Visual Attention
• Location-based: moving attention from one
place to another
• Object-based: attention being directed to one
place on an object
Object-Based Visual Attention
• Egly et al. (1994)
– Participants saw two side-by-side rectangles,
followed by a target cue
– Reaction time fastest when target appeared where
– Reaction time was faster when the target
appeared in the same rectangle
Object-Based Visual Attention
• The enhancing effect of attention spreads
throughout the object
Attention can be based on the
– Environment
static scenes or scenes with few objects
– Specific object
dynamic events
Caption: Steps in Treisman’s feature integration theory. Objects are
analyzed into their features in the preattentive stage, and then the
features are combined later with the aid of attention.
Feature Integration Theory (FIT)
• Preattentive stage
No effort or attention
Unaware of process
Object analyzed into features
Feature Integration Theory (FIT)
• Treisman and Schmidt (1982)
– Participants report combination of features from
different stimuli
– Illusory conjunctions occur because features are
“free floating”
Caption: Stimuli for illusory conjunction
Feature Integration Theory (FIT)
• Focused attention stage
– Attention plays key role
– Features are combined
Feature Integration Theory (FIT)
• Treisman and Schmidt (1982)
– Ignore black numbers and focus on objects
– Participants can correctly pair shapes and colors
Feature Integration Theory (FIT)
• R.M.: Patient with Balint’s syndrome
– Inability to focus attention on individual objects
– High number of illusory conjunctions reported
Feature Integration Theory (FIT)
• Mostly bottom-up processing
• Top-down processing influences processing
when participants are told what they would
– Top-down processing combines with feature
analysis to help one perceive things accurately
Physiology of Attention
• Attention enhances neural responding
• Attentional processing is distributed across a
large number of areas in the brain
Physiology of Covert Attention
• Monkey trained to fixate eyes on a dot while a
peripheral light was flashed
– Fixation only: monkey was to release bar when
the fixation light dimmed
– Fixation and attention: monkey was to release bar
when peripheral dimmed
Caption: Top: Stimuli for Colby et al.’s (1995) selective attention
experiment. The monkey always looked at the fixation light. A
peripheral stimulus light was flashed inside the circle on the right.
Below: (a) Nerve firing when the monkey was looking at the fixation
light but was not paying attention to the peripheral light; (b) firing
when the monkey was looking at the fixation light and paying
attention to the peripheral stimulus light.
Physiology of Covert Attention
• Single cell recordings showed monkey’s
response when paying attention to the
peripheral light was not caused by changes of
the stimulus on the retina but by the monkey’s
attention to light
Attention Processing Distributed Across the
• Using fMRI to detect cortical activity during a
search task
Attention to an expected direction of motion
caused brain activity to increase in a number
of brain areas
Caption: The results of Schulman and coworkers’ (1999) experiment,
showing some of the brain areas activated by viewing the moving
dots. The graphs indicate the amount of brain activity when
participants were cued to pay attention to a particular direction of
movement (red lines) and when they were cued to just passively
view the moving dots (green lines).
Attention in Social Situations: Autism
• Autism: serious developmental disorder in
which one of the major symptoms is the
withdrawal of contact from other people
Attention in Social Situations: Autism
• Can solve reasoning problems that involve
social situations
• Cannot function when placed in an actual
social situation
• This may be due to the way those with autism
observe what is happening
Attention in Social Situations: Autism
• Non-autistic observers look to eyes to assess
emotional reaction
• Autistic observers look to the mouth or off to
the side of the face to assess emotional
Attention in Social Situations: Autism
• Autistic people’s attention (or lack thereof)
may be one way in which they see things
differently in the environment