attention. what is attention? "everyone knows what attention is. it is the taking possession...

Attention

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

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?

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?

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

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

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

Five functions of attention (from Medin) Perceptual

1. Focusing

2. Perceptual enhancement

3. Binding

Complex Tasks4. Automaticity (sustaining behavior)

5. Task Selection

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

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

Inhibition of return: bias against previously attended to areas

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

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)

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

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

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’

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)

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.

Sperling Array of 12 letters 50 msec. presentation

7 I V F

X L 5 3

B 4 W 7

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.

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

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.

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?

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

Filter acts early after sensory stage Problem

Some ‘unattended’ info gets through Moray 1959 (can still hear our name in unattended channel)

INPUT

Sensoryregister

Selectivefilter

Detectiondevice

Short-termmemory

RESPONSE

Determine who is speaking

Danger signals, one’s name

Based on current goals

Revised conceptualization: some stable high priority info is checked without attention

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

InThe

PicnicBasket

SheHad

Peanut

ButterBookWoodLiveAtOn

Unattended

CatLargeDay

AppleFriendHouseSpoon

CapSandwiches

AndChocolate

CakeCrab

Treisman

Suggests that the filter/attenuator is occurring somewhat later but still before information reaches short-term/working memory

INPUT

Sensoryregister

Attenuationcontrol

Detectiondevice

Short-termmemory

RESPONSE

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

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

Late selectionPost-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.”

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?

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

Sensoryregister

Detectiondevice

Workingmemory

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

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.

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)

Capacity Model Kahneman (1973)

What gets in depends Attention is a resource

to be allocated across tasks

Practiced tasks require less resources Automaticity

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?

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?

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

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

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

PRP and Attentional Blink summary of results

Task 2 RT

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As one can see, with more time between stimulus and probe, attention has ‘returned’and the probe is more readily identified.

% C

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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

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

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

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

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

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

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)

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

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

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)

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

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

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

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

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)

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

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

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

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

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

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

Binding How are features of stimuli integrated into a

perceptible whole?

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

Conjunction Search

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

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RT

(m

s)

Feature Target

ConjunctionTarget

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

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

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

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

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

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

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

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)

+ +.

Quick Demo: Pick a card

I have removed your card!

How? You weren’t paying attention!