Visual Attention & Inhibition of Return 1 st Year Practical 3 Jonathan Stirk & Jasper Robinson.

Visual Attention & Visual Attention & Inhibition of Return Inhibition of Return

11stst Year Practical 3 Year Practical 3

Jonathan Stirk & Jasper Jonathan Stirk & Jasper RobinsonRobinson

What is attention?What is attention?

►““Everyone knows what attention is. It Everyone knows what attention is. It is the taking possession of the mind, in is the taking possession of the mind, in clear and vivid form, of one out of clear and vivid form, of one out of what seem several simultaneously what seem several simultaneously possible objects or trains of thought. possible objects or trains of thought. Focalisation, concentration, of Focalisation, concentration, of consciousness are of its essence.” –consciousness are of its essence.” –James (1890), pp 403-404.James (1890), pp 403-404.

What is attention?What is attention?

► Attention is the process of concentrating on Attention is the process of concentrating on specific features of the environment, or on specific features of the environment, or on certain thoughts or activities. This focusing certain thoughts or activities. This focusing on specific features of the environment on specific features of the environment usually leads to the exclusion of other usually leads to the exclusion of other features of the environment.features of the environment. Colman (2001)Colman (2001)

► But really “attention” is not a unitary But really “attention” is not a unitary conceptconcept Luck & Vecera (2002), Styles (1997)Luck & Vecera (2002), Styles (1997)

Visual AttentionVisual Attention

► It is often thought that we attend what we It is often thought that we attend what we look atlook at

► However, we can process information to However, we can process information to some extent even when our eyes are not some extent even when our eyes are not directly focused on itdirectly focused on it Attention may often precede eye-movementsAttention may often precede eye-movements

► So shifts in attention may be accompanied So shifts in attention may be accompanied by a change in eye fixation or notby a change in eye fixation or not Overt & CovertOvert & Covert shifts shifts

► ‘‘Looking out of the corner of your eye’Looking out of the corner of your eye’

Visual AttentionVisual Attention

►When we inspect visual stimuli or scenes, When we inspect visual stimuli or scenes, what controls the movement of attention?what controls the movement of attention?

► Is attention captured by stimuli/objects or Is attention captured by stimuli/objects or do we intentionally deploy attention?do we intentionally deploy attention?

► In other words is attention controlled by In other words is attention controlled by us or by the stimuli?us or by the stimuli? Top-downTop-down processes versus processes versus bottom-upbottom-up

processesprocesses

Moving Visual AttentionMoving Visual Attention

► ‘‘Spotlight’ metaphorSpotlight’ metaphor One idea is that attention is like a spotlight One idea is that attention is like a spotlight

which moves about and allows us to which moves about and allows us to selectively attend to parts of the visual worldselectively attend to parts of the visual world

Michael Posner (1980) suggested that Michael Posner (1980) suggested that enhanced processing/detection occurs within enhanced processing/detection occurs within this ‘spotlight’ [see also Norman (1968)]this ‘spotlight’ [see also Norman (1968)]

So attention is directed towards ‘So attention is directed towards ‘spacespace’ ’ according to the spotlight model. It is a according to the spotlight model. It is a space-basedspace-based model of attention model of attention

Orienting AttentionOrienting Attention

► Posner (1978), Posner (1980), Posner, Posner (1978), Posner (1980), Posner, Davidson & Snyder (1980) examined the effect Davidson & Snyder (1980) examined the effect of of visually pre-cueingvisually pre-cueing regions of space on regions of space on detecting the presence of a potential targetdetecting the presence of a potential target

► They wanted to know whether causing a shift They wanted to know whether causing a shift of attention to a specific location in space of attention to a specific location in space improved the processing of the subsequent improved the processing of the subsequent stimulusstimulus

► They examined They examined covertcovert shifts of attention shifts of attention No eye-movements allowed!No eye-movements allowed!

Participants told to fixate here and not to look away

2

X

General FindingsGeneral Findings

►Reaction times to detect the presence Reaction times to detect the presence of a stimulus event are of a stimulus event are reducedreduced compared to a control condition [no compared to a control condition [no pre-cue given/uninformative pre-cue pre-cue given/uninformative pre-cue given (enlarged fixation cross)]given (enlarged fixation cross)]

►Presenting an informative pre-cue Presenting an informative pre-cue seems to allow attention to move to seems to allow attention to move to the correct spatial region and the correct spatial region and enhances processing at itenhances processing at it

Investigating top-down and Investigating top-down and bottom-up controlbottom-up control

►Posner also manipulated the TYPE of Posner also manipulated the TYPE of pre-cue used in his taskpre-cue used in his task Central Central cue (as in previous example, e.g. cue (as in previous example, e.g.

a directional arrow) ora directional arrow) or PeripheralPeripheral cue cue

►A peripheral cue indicates exactly A peripheral cue indicates exactly where the target stimulus may appear where the target stimulus may appear using a peripheral event which using a peripheral event which captures attentioncaptures attention E.g. an illuminated box (see next slides)E.g. an illuminated box (see next slides)

Peripheral CuePeripheral Cue

Peripheral CuePeripheral Cue

Peripheral CuePeripheral Cue

X

Peripheral CuePeripheral Cue

Peripheral CuePeripheral Cue

General Findings – Peripheral General Findings – Peripheral CueCue

► Peripheral cues were found to orient Peripheral cues were found to orient attention too, with responses being faster attention too, with responses being faster [reaction times reduced] compared to a [reaction times reduced] compared to a control (no cue) conditioncontrol (no cue) condition

► So far the pre-cue has always been valid So far the pre-cue has always been valid (i.e. 100% predictive of where the target will (i.e. 100% predictive of where the target will be, if it is presented)be, if it is presented)

► So what happens if the pre-cue is invalid So what happens if the pre-cue is invalid (doesn’t predict the location of the target) or (doesn’t predict the location of the target) or uninformative (only predict target location uninformative (only predict target location on 50% of trials)?on 50% of trials)?

Costs & BenefitsCosts & Benefits

► If the cue is 100% invalidIf the cue is 100% invalid RT to detect target RT to detect target increasesincreases compared to a compared to a

control/neutral conditioncontrol/neutral condition► There is a There is a costcost to cueing attention to the wrong location! to cueing attention to the wrong location!► Suggests that attention has moved in the wrong directionSuggests that attention has moved in the wrong direction

If a peripheral cue is non-predictive/uninformative If a peripheral cue is non-predictive/uninformative (only correctly predicts target on 50% of the trials) (only correctly predicts target on 50% of the trials) we still react faster to the cued location suggesting we still react faster to the cued location suggesting that peripheral cues cause that peripheral cues cause REFLEXIVEREFLEXIVE shifts of shifts of attentionattention

► We can therefore examine the orienting of We can therefore examine the orienting of attention in terms of costs and benefits of attention in terms of costs and benefits of cueingcueing

Today’s PracticalToday’s Practical

►We are going to use the Posner We are going to use the Posner paradigm to examine another important paradigm to examine another important finding in attentional researchfinding in attentional research

►How long does the facilitation effect of a How long does the facilitation effect of a valid pre-cue last?valid pre-cue last? Normally a valid Normally a valid peripheralperipheral pre-cue pre-cue

facilitates processing at and around that facilitates processing at and around that locationlocation

However, under certain conditions However, under certain conditions responses to a pre-cued location can be responses to a pre-cued location can be slowed down (inhibited)slowed down (inhibited)

► The time-delay (CTOA) between presenting the cue The time-delay (CTOA) between presenting the cue and the target has to fall within certain parametersand the target has to fall within certain parameters

► If the delay is too large then attention moves away If the delay is too large then attention moves away (is disengaged) from the location and any further (is disengaged) from the location and any further processing at that location is temporarily processing at that location is temporarily inhibitedinhibited, , slowing down a response to a target that then later slowing down a response to a target that then later appears thereappears there

► This This reversalreversal from a facilitatory to an inhibitory effect from a facilitatory to an inhibitory effect is called is called Inhibition Of Return Inhibition Of Return [Posner & Cohen (1984)][Posner & Cohen (1984)]

Inhibition Of Return - IORInhibition Of Return - IOR

CUEISI/cue-target

interval TARGETTime

CTOA

Manipulating CTOAManipulating CTOA

► As the CTOA As the CTOA increases from 0 to increases from 0 to approx. 200 ms, approx. 200 ms, valid cueing is valid cueing is facilitatoryfacilitatory

► Between 200-300 ms Between 200-300 ms the lines cross the lines cross indicating that valid indicating that valid cueing now causes cueing now causes slowerslower responses to responses to the cued locationthe cued location

Black (filled circles) are valid trials

White are invalid trials

Posner & Cohen (1984)Posner & Cohen (1984)

Posner et al only found this inhibitory effect for peripheral pre-cues i.e not for central cues!

Cued (valid)

Uncued (invalid)

Another IOR definitionAnother IOR definition

► IOR is “…a reduced perceptual priority IOR is “…a reduced perceptual priority for information in a region that has for information in a region that has recently enjoyed a higher priority” recently enjoyed a higher priority” Samuel & Kat (2003), p897.Samuel & Kat (2003), p897.

Our experimentOur experiment

►We are going to manipulate 3 levels of We are going to manipulate 3 levels of CTOA and investigate differences CTOA and investigate differences between them.between them.

►We will use CTOA’s of 150, 200 and 400 We will use CTOA’s of 150, 200 and 400 msms

►Our null hypothesis will be that Our null hypothesis will be that facilitation is facilitation is notnot affected by CTOA affected by CTOA

►Our experimental hypothesis will be Our experimental hypothesis will be that as CTOA increases, facilitation that as CTOA increases, facilitation decreasesdecreases

Measuring size of the effectMeasuring size of the effect

►We can measure the size of the We can measure the size of the facilitatory effect by taking a difference facilitatory effect by taking a difference score for valid and invalid trialsscore for valid and invalid trials Difference score = RT Invalid – RT ValidDifference score = RT Invalid – RT Valid E.g for a short CTOA (say 50ms) we expect E.g for a short CTOA (say 50ms) we expect

people to be faster on valid trials than people to be faster on valid trials than invalid ones (a facilitatory effect) by say 25 invalid ones (a facilitatory effect) by say 25 ms.ms.

405 - 380 = +25ms (facilitatory effect of 405 - 380 = +25ms (facilitatory effect of cueing)cueing)

Example DataExample DataR

T d

iffer

ence

(m

secs

) +

-

100 300200 400

CTOA

As CTOA increases, facilitation decreases

Facilitation

Inhibition

IOR begins to start

around here

What role might an IOR What role might an IOR mechanism have?mechanism have?

► IOR biases attentional orienting IOR biases attentional orienting awayaway from from previously inspected locationspreviously inspected locations

► When we visually search an environment, we When we visually search an environment, we want to avoid re-inspecting (attending) want to avoid re-inspecting (attending) already visited locations/objects.already visited locations/objects. IOR prevents us returning to recently inspected IOR prevents us returning to recently inspected

locations using an inhibitory mechanismlocations using an inhibitory mechanism We have a bias towards new/un-inspected locationsWe have a bias towards new/un-inspected locations

► Klein (1988)- IOR can facilitate effective visual Klein (1988)- IOR can facilitate effective visual search / foraging behavioursearch / foraging behaviour

OK, so that’s the theoryOK, so that’s the theory

►Let’s look at building this experiment Let’s look at building this experiment in E-Prime and collecting some data.in E-Prime and collecting some data.

►ExperimentExperiment Peripheral cueing taskPeripheral cueing task

►Aim: Decide whether an X appears at one of 2 Aim: Decide whether an X appears at one of 2 possible locationspossible locations

►If it does then press SPACEIf it does then press SPACE►If it doesn’t then don’t press anythingIf it doesn’t then don’t press anything

Target Target detectiondetection task vs. a discrimination task task vs. a discrimination task

DesignDesign

►Factors to control/manipulateFactors to control/manipulate % of trials when target is present/absent% of trials when target is present/absent Location of pre-cue (Left or Right)Location of pre-cue (Left or Right) Location of target [when present] (Left or Location of target [when present] (Left or

Right)Right) Cue-target onset asynchrony (150, 200 & Cue-target onset asynchrony (150, 200 &

400ms)400ms)►Manipulate this as a Manipulate this as a within-subjects IV (3 within-subjects IV (3

levels)levels)

Minimum number of trials needed Minimum number of trials needed to control and manipulate all to control and manipulate all

variablesvariables► 22 (present/absent) x (present/absent) x 22 (Cue L/Cue R) x (Cue L/Cue R) x 22

(Target L/Target R) x (Target L/Target R) x 33 ( CTOA 150, 200 & ( CTOA 150, 200 & 400) =400) = 2424 trials for a balanced design trials for a balanced design

► So we can use any multiple of 24 for the number of So we can use any multiple of 24 for the number of experimental trialsexperimental trials

► These trials break down into valid and These trials break down into valid and invalid trialsinvalid trials Valid trialsValid trials

► Target appears in the Target appears in the cuedcued location location Invalid trialsInvalid trials

► Target appears in the Target appears in the uncueduncued location location

Time to build!Time to build!

►Ok, so we are going to build a Ok, so we are going to build a peripheral cueing task in E-Prime!peripheral cueing task in E-Prime!

►This is going to be difficult and will This is going to be difficult and will teach you some new E-Prime skillsteach you some new E-Prime skills

►Open up E-Prime and select to create Open up E-Prime and select to create a new blank experiment.a new blank experiment.

+ + +

+

+

OR

FIX CUE Variable ISI

VALID

INVALID

50:50 ratio

Target