Attention
What is it?
What control do
We have over it?
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Everyone knows what attention is. It is the
taking of possession by the mind, in clear
and vivid form, of one out of what seem
several simultaneously possible objects or
trains of thought. Focalization,
concentration, of consciousness are of its
essence….. It implies withdrawal from
some things in order to deal more
effectively with others, and is a condition
which has a real opposite in the confused,
dazed, scatterbrained state which …. Is
called distraction. - William James (1890)
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Read the bold print.
Somewhere Among hidden the in most the spectacular
Rocky Mountains cognitive near abilities Central City is
Colorado the an ability old to miner select hid one a mes
sage box from of another. gold. We Although do several
this hundred by people focusing have our looked
attention for on it, certain they cues have such not as
found type it style.
What do you remember from the regular print text?
What does this tell you about selective attention?
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Focused or Selective Attention
Task: Present people with two or more
stimulus at the same time and instruct them to
respond to only one.
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Attention
Perceptual processes - Parallel & Unlimited
Attention - Serial and Limited
At some point there is a bottleneck.
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We need to select which input
will be attended to (and
further processed) and which
will be ignored (and lost).
Questions
1) Is bottleneck before or after meaning has
been processed?
2) How do we select what to attend to?
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Dichotic Listening Task (Cherry, 1953)
- two messages presented
Shadowing task - repeat message presented in
one ear as you are hearing it.
Dependant Measures
1) Shadowing performance (errors,
hesitations, omissions) indicate
that attention has been diverted.
2) What is recalled from the
unattended message?
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Dichotic Listening Task
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Dichotic Listening Results
Physical attributes of unattended channel are
detected (e.g., Male . vs. female voice; Human
vs. musical instruments).
Semantic (meaning) attributes of unattended
channel were missed (e.g., Don’t notice switch to
foreign language). No content was remembered,
even when the unattended stream was the same
word presented 35 times (Moray, 1959).
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Broadbent’s Early Filter Model
• An early-selection model - filtering occurs
before incoming stimuli are analyzed to the
semantic level
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Parts of the filter model
• Sensory store - Holds incoming information for a
short period of time
• Filter - Analyzes messages based on physical
characteristics like tone of voice, pitch, location of
stimulus (which ear)
• Detector - Information is processed to determine
meaning
• Short-term memory - Holds information for general
processing
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Broadbent’s Split-Scan Study
• Present letters at the same time to each ear
H
:-)
M
R
:-)
S
W
:-)
P
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Broadbent’s Split-Scan Study
• Two conditions:
1.) Repeat back all letters in any order
2.) Repeat back letters in the order they were
presented
H
:-)
R
:-)
W
:-)
M
Condition 1 (Any Order):
H, R, W, M, S, P
S
Condition 2 (In Order):
H, M… P?
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Split-Scan Results
• Condition 1 (repeat back in any order)
– 65% correct letter report
– Would report all letters presented to one ear first
• Condition 2 (repeat back in presented order)
– 20% correct letter report
• Suggests that the letters to one ear were stored briefly
while those of the other ear were processed.
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The early filter model explains…
• How we can pay attention to one ear and
ignore stimuli coming into the other ear
• Why we prefer to process stimuli that come
in to one ear all at once as opposed to
switching channels
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Problems with early filter model
Back at the cocktail party. You’re talking to
your friend and ignoring all the other
conversations…
Until someone across the room says your
name. Then you turn your head.
But you were supposed to be ignoring other
conversations - what happened?
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Moray (1959) - “cocktail party effect”
subjects could often detect their own name
“fire” or context relevant words on
unattended channel. How could
this happen if unattended
information does not pass
through filter for pattern
recognition?
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Late selection models Deutsch & Deutsch, 1963)
information is selected after meaning has been
processed.
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Evidence against:
(Treisman & Riley, 1969)
-Used shadowing task asked subject to
indicate when they detected a target in
either message.
Many more targets were detected on the
shadowed message.
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Corteen & Wood (1972): Experiment in which
subjects were first given mild shocks whenever
certain words--city names--were presented in a
long list. This set up a conditioned autonomic
response, the galvanic skin response or GSR,
which measures changes in the resistance of
the skin with sweating. After training, just
seeing the city name increased GSR.
Then Ss SHADOWED prose in one ear and
heard a list of words in the other. The list
included the city names plus new city names,
and neutral words. Measured GSR.
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Coch et al., (2005) same task as Treisman
1969 except ERPs were recorded to determine
if target words were being processed. ERPs
100ms after target presentation (indication that
the target has been perceived)
were greater for targets in the
attended compared to the
unattended message.
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Treisman (1960)
Found that attention
could be easily
switched to the
unattended ear when
semantic content of
the message shifted
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Treisman’s attenuation model
• Still an early-selection theory
• Instead of a filter, an attenuator analyzes
incoming messages
– Physical characteristics
– Language - Groups of syllables/words
• Attended messages are given more priority
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Attenuation = loss of signal strength
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The Dictionary Unit
• Both messages gets passed on to the
dictionary unit
Threshold =
Smallest signal
strength that
can just be
detected
Easily detected
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Attenuation explains…
• Hearing your own name when that stream is
supposed to be ignored
• Switching channels in order to make a
complete sentence
• But a specific dictionary unit? That seems
like a cop-out.
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Problems with early selection
• MacKay (1973)
• Ambiguous sentences: “They were
throwing stones at the bank”
– Bank = Financial institution or side of a river?
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MacKay Method & Results
• Dichotic listening
– Attended stream: Ambiguous sentence
• “They were throwing stones at the bank.”
– Unattended stream: Biasing word
• “River” or “Money”
• The biasing word had an effect!
– If “money”, the ambiguous sentence was more
likely interpreted as financial institution
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What does this mean?
• The unattended stream was being
processed, and it wasn’t a name or another
low-threshold word
– Not early-selection
– Not an attenuator
• The word was actually being processed to
the semantic level (to its meaning)
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So what’s right?
• There’s evidence for EVERYTHING!
• That’s no good.
• Lavie (1995) - Where the filtering occurs
depends on task load
– How much of a person’s cognitive resources
are used in a task
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Perceptual Load Theory:
The location of the filter is Flexible
• High-load task: Difficult, requiring most of
someone’s cognitive resources
– Only selected items are processed
• Low-load task: Easier, cognitive resources
are left over
– Can process additional information
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Johnston & Heinz (1978) Multimode attention
theory:
Selective attention can operate anywhere,
early or late, but the later it operates the
more costly in terms of resources (mental
effort) it is
Demonstrated this using a task which
showed that processing difficulty increased
as the lateness of attention selection
increased
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Dual Task Procedure
1) Dichotic listening with shadowing
Independent Variables:
messages physically differ (different sex
Speakers or do not (same sex speakers).
2) Detect light stimuli on a computer screen.
Dependent Measure: time to respond to
presence of light
Results: Early (physical) differences created
much less slow down than Late (semantic)
differences.
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More than 2 messages (created so
they appear to come from different
sources), does not increase response
times. Processing unattended
message does not take resources,
selecting it does.
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Summary
1. Filter is flexible
- depends on the task
2. Later selection takes more effort.
3. Effort depends on selection not
on amount of background.
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Selective Visual Attention
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Spot Light/Zoom Lens Metaphor
• Can be directed to specific areas
• Can be diffuse or focused
- trade off in concentration
• Concentrated at the center, fuzzy at
the borders
• Limited capacity
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Muller et al., 2003
Zoom Lens Theory predicts that if you are
focusing on two items, your attention should
also be good for any item that falls between
the two items.
Evidence show that if attention
is split between two cued
locations, detections of items
falling between is poor.
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Figure 3.1 (a) Shaded areas
indicate the cued locations and
the near and far locations are
not cued. (b) Probability of
target detection at valid (left
or right) and invalid (near or
far) locations. Based on
information in Awh and
Pashler (2000).
When attention is split,
it can act like multiple spot
lights. With unattended areas
falling in spaces between
attended areas.
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What Happens to Unattended Stimuli?
Evidence from Neglect Patients.
Shown some pictures to the non-neglected
visual field and others to the neglected visual
field.
Later asked to identify the same pictures in a
degraded version. They are just as fast with
those that had been presented to the neglected
as the non-neglected visual field (priming).
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Neurological evidence also indicates that
when the overall attentional load of a task was
low, neglect patients showed increased brain
activity to task irrelevant items presented in
the neglected visual field (some processing is
going on) even though the patients are not
consciously aware of the stimuli.
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Hemi neglect
Patients Suffering From 'Hemi
-neglect' Ignore Things On Their
Left, But They See Them Nonetheless
Click here to see Science Daily article (05/15/08.)
This study demonstrates that in hemi-neglect the left
part of the world is not a 'blind' region: in a way,
patients read unconsciously what is there. However,
the patients cannot make conscious use of this
information
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Attention as Capacity
• Attention is the process of allocating mental
resources to various cognitive tasks
Factors effecting allocation of Attention
-Anxiety
-Salience and Distinctiveness
- Relevance
-Task demands
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Cross- Modality Effects
Ventriloquist Illusion
Rubber Hand Illusion
Phantom Limb Pain (begin at 13:00)
Body Swap Illusion
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Disorders of Visual Attention
Hemi-neglect – (Historical note) President
Woodrow Wilson after suffering two
strokes developed hemi neglect. When
colleagues came to visit him, he failed to
respond to them until they were escorted to
his right side. He denied he had a problem
and planned to run for a third term as
president until his wife finally intervened.
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Spatial Extinction: can detect a single item in
both the left and right visual fields but, under
conditions double simultaneous stimulation fail
to detect the item in the left field.
Presented
Perceived
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When stimuli is presented in the neglected
field but has no competition for attention
from the non-neglected visual field, the image
is perceived. When there is competition for
attention from the non-neglected visual field,
attention is given only to the non-neglected
visual field.
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Two Attention Systems (Corbetta)
Goal directed system - preparing and
applying goal-directed (top-down) selection
for stimuli and responses. Effected by
expectations, knowledge and/or intentions.
Stimulus driven – (bottom-up) specialized
for the detection of behaviorally relevant
stimuli, particularly when they are salient or
unexpected. Circuit breaker .
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The area were the two attention systems
combine is in the parietal lobe. There is
competition for attention from the two
attentional systems. Hemi- neglect can occur
due to impairment in either the goal-directed
or the stimulus driven systems. Results in a
failure to activate the parietal cortex enough
to capture attention to that visual filed.
Hemi-neglect is a disorder of Attention –
not of perception.
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Reducing Neglect: Physiotherapy
Hemi-neglect patients
when asked to point
straight ahead – point
several degrees to the left.
Prism glasses that shift the visual field 10
degrees to the right allow patients to use the Goaldirected (top-down) processes to direct more
attention to the neglected left visual field.
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Demonstration
• I will show you a scene quickly.
• Report first the black numbers.
• Report what you see at each of the 4
locations.
Mask
+++
Illusionary conjunctions
• We tend to put different features from
different objects together.
• Some brain damaged patients (parietal lobe)
show illusionary conjunctions even when
the patients were allowed to view the
stimuli for 10 seconds.
Feature Integration Theory
Find the Green X
X
X
X X
X
X
X XX
X
X
X XX
Feature search
X O X O
X O X
O X O XO
X
Conjunction search
Treisman & Gelade 1980
Typical Findings & interpretation
• Feature targets pop out
– flat display size function
3000
Feature Target
• Conjunction targets
demand serial search
2500
Conjunction
Target
RT (ms)
2000
– non-zero slope
1500
1000
500
0
1
5
15
Display Size
30
Find
Which is more difficult?
Find
Which is more difficult?
Feature integration theory
• Attention is the “glue” that combines the
information from the what and where systems.
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Multi-tasking
Ophir et al (2009) Correlation between
multitasking and distractibility.
When asked to do two tasks at once,
participants who reported being multitaskers
performed less well on the main task than did
non-multitaskers. Perhaps multitaskers are
just less able to focus attention.
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Cell Phone Use
Hyman et al (2009)
Cell phone users less
likely (25%) than nonusers (51%) to notice a
unicyling clown!!!
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Practice and Dual Task
Performance
Spelke, Neisser et al (1976)
Two subjects read short stories while writing lists
of words at dictation. After some weeks of
practice, they were able to write words, discover
relations among dictated words, and categorize
words for meaning, while reading for
comprehension at normal speed. The performance
of these subjects is not consistent with the notion
that there are fixed limits to attentional
capacity.
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Automatic vs. Controlled
• Automatic Processes
– Fast and efficient
– Unavailable to
consciousness
– Unavoidable
– Unintentional
• Controlled Processes
–
–
–
–
Slow and less efficient
Available to consciousness
Controllable
Intentional
Attention as executive control
• In contrast to capacity theories (which see
attention as a limitation) considering it as
executive control of possibly conflicting
multiple goals makes attention instead a
source of efficiency
• Evidence: Psychological Refractory Period
Psychological Refractory Period
• 2 stimuli and 2 responses
– Light: press button
– Tone: press foot pedal
• Varying SOAs
– At short SOAs, response to task 2 takes longer
• Varying stimulus processing difficulty
– Lengthening processing of stimulus 1 slows RT to
stimulus 2
– Lengthening processing of stimulus 2 does not slow
response to stimulus 2!!
PRP: Surprising Results
Processing
Of Stimulus
Central
Response
Executive to Stimulus
S1
R1
S2
R2
S1
R1
S2
S1
R2
R1
S2
R2