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1. Attention
‫در‬ ‫شده‬ ‫ارائه‬
‫تخصصی‬ ‫کارگاه‬
‫توجه‬ ‫توانبخشی‬
‫شناختی‬ ‫های‬ ‫هفته‬ ‫آخر‬ ‫های‬ ‫کارگاه‬ ‫سری‬ ‫از‬
‫تابستان‬1396
‫تنظیم‬ ‫و‬ ‫تهیه‬:‫علیزاده‬ ‫مهدی‬ ‫دکتر‬

2. What is attention?
 "Everyone knows what attention is. It is the
taking possession by the mind in clear and
vivid form, of one out of what seem several
simultaneously possible objects or trains of
thought...It implies withdrawal from some
things in order to deal effectively with
others."
 William James

3. What is attention?
 Though we may talk about it in the following
ways…
 “I can only do so much at once!”
 “I missed the play on the field, I wasn’t paying
attention.”
 “Pay attention to me!”
 “I need to focus.”
 “She has attention deficit disorder.”
 Are they all referring to the same thing?

4. What is attention?
 What was first viewed as simple bottlenecks is really
much more complex
 Attention determines how information is processed
by the cognitive system…
 …and vice versa
 Cognitive Control of Attention
 Limits to attention may be processing limits
 In some ways however we really don’t know much
more about it than folk theories.
 So what do we know?

5. Attention
 What is Attention?
 Attention is the control of sensory input and
cognitive resources
 Input = how much/ what gets in
 Control = what guides attention
 Internal
 External

6. Other distinctions
 Task-defined and Maintenance of activity
 Descriptive notion of attention defined by the task used in
the study (e.g. if they answer a certain way they are
attending to that stimulus), or continued action
 Doesn’t speak to underlying mechanisms
 Process-oriented
 Attention as a psychological process
 Involves selection among alternatives and improving the
effectiveness of mental processes

7. Other distinctions
 Perceptual Attention vs. Attention in Complex
Tasks
 Perceptual
 Attention involved in the enhancement and selection
of stimulus input from the environment
 Complex Tasks
 Attention used for non-automatic tasks and task
selection

8. Five functions of attention (from Medin)
 Perceptual
1. Focusing
2. Perceptual enhancement
3. Binding
 Complex Tasks
4. Automaticity (sustaining behavior)
5. Task Selection

9. Paradigms of Attention Research
 Cuing
 Analyze the orienting process and comparison of
processing attended vs unattended stimuli
 Search
 Analyze how attention eliminates interference from
irrelevant stimuli
 Filtering
 Analyze how attention eliminates interference from
irrelevant stimuli and the stages at which such stimuli are
suppressed
 Dual-Task
 Analyze how attention is involved in the coordination of
multiple tasks

10. Cuing
 Participants are led to expect a specific stimulus to
be presented in a particular manner
 Example: Spatial cuing
 Types of cues
 Valid vs. Invalid
 Does the target appear at the cues location or not
 Peripheral (exogenous) vs. Central (endogenous or
symbolic)
 Predictive (target is more often than not consistent with
cue) vs. Non-Predictive (target is as likely to appear
anywhere else same as the cued location)
 Ex. 80% predictive or 50-50% chance at being valid or not

11. Inhibition of return: bias against
previously attended to areas

12. Cuing
 Predictive/Symbolic
 Elicits long-lasting orienting of attention but takes a bit (100-200ms)
for attention to shift due to being a symbolic cue
 Predictive/Peripheral
 Rapid (50-100ms after cue onset) and long-lasting
 Non-predictive/Symbolic
 No real orienting effect as there is no real motivation to shift attention
 Non-predictive/Peripheral
 Rapid orientation but doesn’t last long
 If cue does appear at location (valid) this will be detected much more
quickly with shorter cue-target onset
 With more delay, attention shifts elsewhere and actually RT is slowed
for valid trials
 Inhibition of return

13. Search
 Look for stimuli embedded
among non-target stimuli
 Slopes and set size
 Flat slopes indicate stimuli
are processed independently
(parallel search or
automatic), no interference
from non-targets
 Steep slopes
 Serial search: attention
shifted from one item to
the next until the target is
found. Or…
 Limited-capacity parallel
search (parallel but slower
due to set size increase)

14. Filtering
 Dichotic Listening Task
 See how well we attend to message or
how much of ignored gets through
 Stroop task
 Blue Red
 Word processing ok in general, but if reporting color,
word can interfere
 Global/Local
 Navon letters: slower to report local features if global
does not match
 However size can affect

15. Filtering
 Flankers
 H T H T T T
 Respond what middle is (one response for T, a different
one for H)
 RT is slowed when flankers have a different response associated
with them (HTH), unless far enough apart
 Can show the spread of attention to nearby areas
 Negative Priming
 B
 Particular letter requires a response
 RT slowed when unattended letter later is the to-be-
attended letter
 Previous inhibition affects later processing
A

16. Dual-Task
 How much interference?
 If involve the same cognitive processes, paying
attention to one will lead to a decrease in
performance on the other
 If independent, no interference
 However, in some cases increased difficulty in one task
will result in the other beginning to interfere
 So not necessarily same resources involved, but a reflection of
cognitive ‘load’

17. Focusing
 Perceptual Enhancement
 Lu & Dosher (1998)
 Attention acts as sensory amplifier in general, not just signal
amplifier
 Performance should improve in low noise situations
 If lots of noise, attention will amplify that as well and so
performance will not improve with focus of attention
 What gets in?
 Early Selection
 Attention operates to help prevent sensory/perceptual overload
 Late Selection
 Attention serves to protect higher level cognitive processes (e.g.
working memory)

18. Sensory Memory (Sperling 1960)
 Participants view a briefly presented array of
letters.
 Change the duration between presentation of
array and the recall tone.
 Report as many characters as possible.

19. Sperling
 Array of 12 letters
 50 msec. presentation
7 I V F
X L 5 3
B 4 W 7

20. Sperling
 Full-report
 Report as many items as possible
 Recall (no delay) = ~4 items
 Recall decreased dramatically with tone delay
 Suggests a limit (‘span of apprehension’) to
what can be perceived.

21. Sperling
 Partial-report paradigm
 Tone cued which line of the array to recall
 High = top line
 Medium = middle line
 Low = bottom line
 Compare recall across rows
7 I V F
X L 5 3
B 4 W 7

22. Sperling
 Recall with no delay
 Regardless of row asked to
recall, about 3/4 of the items
would be, or 9 on average
for 12 item presentation
 Conclusions:
 Lots of information gets in and
receives some initial processing
 Lasts a short time
 Same pattern of results as full
report with tone delay
 Sensory memory is rather large
but has a short duration.

23. Focusing: Selecting Channels
 Early Selection
 Attention operates early on to
protect low level processes
from being overloaded
 Late(r) Selection
 Operates after meaning has
been extracted from incoming
stimuli
 Working memory
 If we don’t use the
information…it is lost
 Cocktail Party Paradigm
 Dichotic listening
 If early sensory systems do not
limit the information that is
processed, when does selection
take place?

24. What Gets In?
 Early idea: Only what is specifically attended
to gets in
 Broadbent’s bottleneck (1958)
 One sensory input at a time processing
 Dichotic listening
 Filter is flexible and can shift, but only what
is focused on gets to later processing

25.  Filter acts early after sensory stage
 Problem
 Some ‘unattended’ info gets through
 Moray 1959 (can still hear our name in unattended channel)
I
N
P
U
T
Sensory
register
Selective
filter
Detection
device
Short-term
memory
R
E
S
P
O
N
S
E

26. Determine who is speaking
Danger signals, one’s name
Based on current goals
Revised conceptualization: some stable high priority
info is checked without attention

27. Early/Late Selection
 Such a model comes from Triesman
(1960)
 All in but some in attenuated form
 More relevant, less attenuated
 In the example here, Ss report hearing
the whole sentence
 Cocktail Party effect:
 If meets certain criteria, will be
attended (flexible bottleneck)
 Capacity
 Limit for the amount of information
(and the amount of resources) available
at any one time.
 Although ‘early’ selection, key
differences compared to Broadbent’s
include:
 All info gets in initially for at least
some basic low level processing
 Possibility for flexible or multiple
filtering
Attended
In
The
Picnic
Basket
She
Had
Peanut
Butter
Book
Wood
Live
At
On
Unattended
Cat
Large
Day
Apple
Friend
House
Spoon
Cap
Sandwiches
And
Chocolate
Cake
Crab

28. Treisman
 Suggests that the filter/attenuator is occurring
somewhat later but still before information reaches
short-term/working memory
I
N
P
U
T
Sensory
register
Attenuation
control
Detection
device
Short-term
memory
R
E
S
P
O
N
S
E

29. Late Selection
 Deutsch & Deutsch (1963), Norman (1968)
 Proposed ideas for a late selection of attended information
 Essentially a different interpretation/version of Treisman
 Both channels of information (in dichotic listening
task) are recognized but are quickly forgotten unless
they are relevant (or strong)
 Info makes it to short-term memory
 Not really all that different from Treisman’s except
the filter comes after meaning is fully processed for
both channels

30. More on Late selection
 Mackay (1973).
 Sophisticated meaning analysis of unattended channel
They threw stones towards the bank
… … … … … money
or
… … … … … river
Subject shadows this
Unattended ear

31. Late selection
Post-Shadowing Test
 Heard 26 ambiguous sentences.
 26 “recognition trials” pick sentence that best
matches meaning of the sentences on the
attended channel:
 “They threw stones toward the side of the river
yesterday.” vs.
 “They threw stones toward the savings and loan
association yesterday.”

32. Late Selection
 Result
 Choice of sentence influenced by word in unattended ear
 Hear: money → More likely to pick “financial institution”
 Hear: river → More likely to pick “river bank”
 When asked about the word in the unattended ear,
participants entirely unaware of unattended word
 Conclusion
 Unattended information was fully processed for meaning
 No attenuation early on, but rather is it relevant to the required
response?

33. Late selection
 Information makes it to the detection/processing of meaning stage and
passed on to STM for further processing and perhaps eventually to LTM
 Both channels are processed fully for meaning, but only one of those
reaches conscious awareness
Sensory
register
Detection
device
Working
memory

34. The end of early selection?
 Not so fast
 Evidence from
neurophysiological
studies studies show
the workings of
attention very early on,
before sensory/
perceptual processing
is complete

35. Recap: Comparison of early/late selection
 So there is evidence for
both early and late
 May be that how attention
is utilized depends on the
task and the current
perceptual load, and
instead be related to
‘attentional resources’
available rather than
bottlenecks.

36. Other ideas
 Lavie (1995) suggested that it may have to do with
perceptual load
 If low load all information will be initially processed
and selection for further processing will take place
after all relevant information has been analyzed
 E.g. flankers task
 In high load conditions, attention acts as a perceptual
filter
 Adding more stimuli to the flankers task suppresses the
effect of the flankers (i.e. they are not making it through
the initial perceptual filter)

37. Capacity Model
 Kahneman (1973)
 What gets in depends
 Attention is a resource
to be allocated across
tasks
 Practiced tasks require
less resources
 Automaticity

38. Attentional Control
 Dual-Task Paradigm
 Participant must perform more than one task at a
time
 In general, two tasks can be performed at once..
 … with a detriment to one task …
 … depending on the type of tasks.
 Driving and talking on the phone- which suffers?

39. Dual-Task
 Psychological Refractory Period and
Attentional Blink
 Refer to the same thing only usually in terms of
RT in the former and accuracy in the latter
 How long does it take a process to “prepare”
for additional work?

40. PRP
 Present two stimuli at about the same time.
 Each stimulus varies on some distinct
psychological dimension
 Example
 Tone (high or Low)
 Letter (‘T’ or ‘Q’)
 Make a forced-choice response to both stimuli
 Instructed to give one response first

41. PRP
 Measure the RT to the Second Response and compare it with
RT in a control situation (respond to second target alone)
 RT typically is longer in the dual task situation even for much
different stimuli
 Differences in RT patterns indicate the presence of central processes
that must be completed before response selection for the second
stimulus can occur
 RT varies as a function of a number of factors such as:
 Perceptual ambiguity of stimuli
 The nature of the response required
 Difficulty of tasks

42. Attentional blink
 Rapid serial visual
presentation of stimuli
 E.g. letters
 Two tasks required of
participant
 Name the white letter
 Target
 Was there an X?
 Probe
 When the time between
target and probe is short,
participants are more likely
to miss the probe

43. PRP and Attentional Blink summary of results
Task 2 RT
0
100
200
300
400
500
600
700
800
0 200 400 600 800 1000 1200
Interstimulus Interval (msec)
Task2RT
Dual Task
Control
.4
.5
.6
.7
.8
.9
1.0
0 200 400 600 800 1000
Stimulus Onset Asynchrony
Control
Experimental
As one can see, with more time between stimulus and probe, attention has ‘returned’
and the probe is more readily identified.
%CorrectProbeDetection

44. PRP and Attentional Blink
 Suggests appears to be a bottleneck in response selection and
consolidating the perception into a reportable memory
 Both tasks use the process before response can be made
 Can’t be used at the same time
 However…
 Shapiro notes in the article there are cases in which no AB is seen
 May be related to stimulus similarity
 Awh et al. (2004)
 Digit response (target) Face response (probe)
 Faces unaffected
 Perhaps competition among multiple limited-capacity resources rather
than (dis)similarity
 Dual task costs can be predicted based on the degree to which each task
calls upon overlapping components of a broad range of resources
 Target hits on resources required for probe processing

45. Multiple Resource Theories
 Pashler (1998)
 Attention
 Perceptual component that acts as both a filter and has
resource limitations
 Bottleneck component corresponding to response selection
 Some information may be blocked early on, but even that which
is not filtered is subject to available resources
 Complex Tasks
 Capacities can be coordinated
 Response selection must occur for one task before next
can be completed
 Coordinated by the Central Executive

46. Resource Theories
 Limitations
 Nature of the limitation is unspecified
 Not really testable
 If two tasks can’t be performed without some
impairment  shared resource which is limited
 If no impairment  they don’t require same resource
 Ambiguous results  multiple resources
 By explaining everything it may not really be able to
provide a true understanding

47. Decision Noise
 An alternative explanation of such results is
that, in tasks that require multiple decisions,
accuracy will decline just because there is
more opportunity to make errors (Shiu &
Pashler, 1994)
 I.e. more noise in terms of signal detection
 Evidence from
 Visual Search
 Spatial Cuing

48. Decision Noise
 Looking for a red T
 Resource perspective:
 If accuracy decreases with
increase in red items but not
with increase in green, we
might conclude…
 Some resource allocated to
red but not green
 Each red item receives
fewer available resources
with increase in red items

49. Decision Noise
 Decision noise
perspective
 More noise with
additional red items 
 More opportunity for
decision error
 Decisions are not made
for green letters, so no
performance detriment
with increase in green
items

50. Decision Noise
 We accumulate evidence over time until
criterion reached
 More time (longer RT)  more accurate
 Less time (quicker), less accurate
 Changes in criterion, sensitivity will influence
speed and accuracy (no need to refer to
resources)

51. Decision Noise
 Resource explanation
 Accuracy better for valid trials
due to resource allocation to
cued location
 Decision noise explanation
 Accuracy based on weighted
combination of noise at non-
target locations and signal+noise
at target location
 Valid trials: hi success due to
more weight given to cued
location
 Invalid: still more weight given
to cued locations, but this is
noise on invalid trials

52. Decision Noise
 Consider the following
experiment
 Exogenous (peripheral)
cue, followed by target,
followed by mask
 (1 or 4 #s)
 Valid, invalid, neutral
(no cue) trials

53. Decision Noise
 According to resource theories there
should be an increase in errors for
invalid trials regardless of number of
masks because attentional resources
are devoted to another area
 However, in single mask condition
target is unambiguous (no noise to
reduce for valid or invalid trials)
 More masks introduce more noise
and make detection more difficult
for invalid trials that do not have the
noise reducing benefits of attention
 A precue allows nontarget
information to be excluded from
the decision (noise reducer)

54. The end of resources?
 Not likely
 Still results, such as those from visual search where
targets are defined by relational cues, that SDT can’t
explain
 ERP evidence in difficult visual search tasks in favor of
shifts of attention for difficult searches
 Noise reduction or signal enhancement?
 In separate experiments Shiu & Pashler noticed decreased
accuracy for neutral trials suggesting attention as noise reducer
 Compare with Lu & Dosher that found evidence later of attention
as signal (+ noise) amplifier

55. Complex action
 What controls where attention is allocated?
 Automatic processing
 Strict: obligatory and completes once started (e.g.
feature detection pop-out)
 Lenient: very reduced cognitive effort involved
 Cognitive control
 Central Executive – coordinates and controls
attention and other cognitive activities

56. Automaticity
 Neisser
 Scan column of letters for a target (e.g. K)
•Both valid and invalid trials
•Measured reaction time (RT) to response
W P D S
J A L Q
A B C D

57. Neisser
 Initially everything in the search set must be scanned…
 …with practice, less is scanned
 Less effort 
 Automaticity (multiple search targets can eventually be found as
quickly as single)
“Practice” with search set
RT 4
2
1
Search Set Size

58. Automaticity
 What can be automatized?
 To what extent can certain tasks be automatized
 Schneider & Shiffrin (1977)
 Visual Search Task
 Search Set
 Memory Set
 Vary the number of elements in each (1, 2, or 4)

59. Schneider & Shiffrin
 Positive and Negative Trials
 Consistent and Variable Mapping
 Variable: Target for one trial
can used as distractor in
another
 E.g. Memory set numbers,
distractors include numbers
 Consistent: Stimulus is either
always a target or always a
distractor
 E.g. Memory set numbers,
distractors letters
 Measure RT to “yes/no” response

60. Schneider & Shiffrin
 General effect: Variable vs.
Consistent
 Variable mapping: increased RT
across search and memory set size
 Slopes flat for Consistent across
search and memory set size
 Consistent mapping allows for
automization and parallel process of
items in search display
 Effects of practice in variable
mapping shows same pattern as
here, with just a general reduction in
RT (i.e. set size effects remain).
 Consistent mapping key to
automaticity

61. Schneider & Shiffrin cont’d.
 Subjects practiced in consistent mapping condition until
search set size was no longer a factor
 Switched to varied mapping situation where those items
were now distractors
 Performance much worse when previously consistently
mapped stimuli were distractors in the target set
 Stimuli were drawing attention away from other items in the
frame
 The cost of automaticity
 Hirst, et al. (1980), some varied mapping situations can improve
with practice

62. Framework for attentional control
 Two parameters influence attentional control
 Bottom-up (stimulus-based)
 Example: sudden appearance of stimulus, abrupt changes in the
stimulus array
 Top-down (goal driven)
 Example: expectancies regarding stimulus information (where,
when)
 Biased competition model (Desimone & Duncan,
1995)
 Bottom-up and top-down sources together bias the
competition among competing stimuli

63. Framework for attentional control
 Attentional template
 Represents task demands and goals (e.g.
searching for a particular shape and location)
 Incoming info compared to template for possible
match
 Attention strengthens neural representation of
info that matches

64. Framework for attentional control
 Stimuli and tasks compete for neural representation/motor
output
 Stroop example, both color and word name compete for vocal
response
 Mutually inhibitory  one to eventually win out
 Competition strongest where stimuli are activating the same
area of cortex
 Interactions among neuronal excitation and inhibiting
responses are biased by both bottom-up and top-down
influences
 Processing can be biased on a number of feature dimensions
(color, shape, location etc.)
 Working memory implicated in top-down biasing

65. Binding
 How are features of stimuli integrated into a
perceptible whole?

66. Feature Integration Theory (Treisman)
 Attention needed to bind information together
into a single representation
 Focusing attention
 Enhances the perceptual signal of the features
involved
 Binds the features together
 Localizes them to some point in space

67. Conjunction Search

68. Typical Findings
 Single Feature Targets
pop out
 Flat display size
function
 Automatic, little to no
attention
 Conjunction Targets
demand serial search
 Non-zero slope
 Require attention
0
500
1000
1500
2000
2500
3000
1 5 15 30
Display Size
RT(ms)
Feature Target
Conjunction
Target

69. Feature Integration Theory
 Treisman & Schmidt
(1982)
 Are end numbers odd or
even?
 What letter and their color
did you see?
 Divided attention leads to
miscombinations of
features (illusory
conjunctions)
 Directing attention to the
location of an object
decreases ICs
2 8X T O

70. Feature Integration Theory
 Simple features are easily distinguished
regardless of set size, but conjunctions are more
difficult to detect with increasing set size
 Attention is required to bind features, while single
features can be detected automatically
 Neuropsych
 Person with bilateral parietal damage and bilateral
attention deficits- when multiple objects are presented
can report features but not the objects to which they
belong

71. Feature Integration Theory
 Mechanisms
 Neurons code conjunctions
 Problem of combinatorial explosion
 Example: bar of light, if 100 neurons needed to represent all
colors and 100 for all possible orientations then 10,000
neurons are needed to process all combinations 1,000,000 if
we add brightness etc.
 Synchronous firing
 Results somewhat inconsistent and still doesn’t
answer how the end result is accomplished

72. Fun with attention
 http://viscog.beckman.uiuc.edu/grafs/demos/1
.html
 http://viscog.beckman.uiuc.edu/grafs/demos/2
.html
 http://viscog.beckman.uiuc.edu/grafs/demos/1
2.html
 http://viscog.beckman.uiuc.edu/grafs/demos/1
5.html

73. Change Blindness
 Visual information accessible to
consciousness is transient
 CB is a phenomenon in which people do not
detect large changes in stimulus array for
features of lesser importance
 Can occur for both dynamic and static scenes
 Why?
 Lack of attention

74. Change blindness
 Phenomenon leads some to suggest there are no internal
representations of scenes or that they are incomplete
 Outside world as an external memory to be probed by our
senses
 Just like certain memories are not readily available unless
‘looked’ for, elements of the environment may not be
perceived without attention
 How would you check whether you were seeing all elements in a
scene?
 Although it seems as if we are perceiving the world as is, we
are only consciously receiving info which is attended to
 The refrigerator light is always on

75. Change blindness
 However it may just be that the comparison
process among representations fails or breaks
down in some way, or the preserved
information may not be in a format that can be
used for conscious change perception
 Some studies find that when told that a change
occurred, Ss can guess where it was even if they
weren’t aware of the change initially

76. Inattentional Blindness
 Linking perception and attention
 What (if anything) do we perceive w/o attention?
 Mack & Rock (1998)
 Participants engaged in another task have an element added at
one point
 Example: judge which line is longer, but add a critical
stimulus on a later trial. After critical trial participants are
asked if they noticed anything unusual (very quick
experiment)
+ +.

77.  Quick Demo: Pick a card

78.  I have removed your card!
 How?
 You weren’t paying attention!

79. ‫تخصصی‬ ‫کارگاه‬
‫توجه‬ ‫توانبخشی‬
‫سپاسگزاریم‬
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