Perceptual Errors in ObjectPerceptual Errors in ObjectRecognition are ReducedRecognition are Reduced

by the Presence of Contextby the Presence of ContextObjectsObjects

M. AucklandM. Auckland11, K. Cave, K. Cave22,,N. DonnellyN. Donnelly11 and F. Gomes-Pinto and F. Gomes-Pinto11

11University of SouthamptonUniversity of Southampton22University of MassachusettsUniversity of Massachusetts

Explanations for Contextual EffectsExplanations for Contextual Effects

nn Description EnhancementDescription Enhancement•• Biederman Biederman (1981)(1981)•• Context activates schema, which facilitates theContext activates schema, which facilitates the

perceptual analysis of objectsperceptual analysis of objects

nn Criterion ModulationCriterion Modulation•• Palmer (1975), Friedman (1979), Palmer (1975), Friedman (1979), Kosslyn Kosslyn (1994)(1994)•• Context activates schema, which lowers theContext activates schema, which lowers the

activation threshold of related objectsactivation threshold of related objects

nn Functional IsolationFunctional Isolation•• Hollingworth Hollingworth & Henderson (1998, 1999)& Henderson (1998, 1999)•• Semantic and perceptual processes isolatedSemantic and perceptual processes isolated•• Effects explained by response biasEffects explained by response bias

Explanations for Contextual EffectsExplanations for Contextual Effects

nn Hollingworth Hollingworth & Henderson (1998, 1999)& Henderson (1998, 1999)provide strong evidence against Descriptionprovide strong evidence against DescriptionEnhancementEnhancement•• Over-estimation of sensitivity when calculatingOver-estimation of sensitivity when calculating d d’’ in in

Biederman Biederman (1981)(1981)•• Two alternative forced choice experiment toTwo alternative forced choice experiment to

remove response biasremove response bias

nn Nature of forced-choice experiments did notNature of forced-choice experiments did notprovide such strong evidence againstprovide such strong evidence againstCriterion ModulationCriterion Modulation

Aim of ExperimentAim of Experiment

nn This study attempted to use an alternativeThis study attempted to use an alternativemethod of removing response bias to assessmethod of removing response bias to assessCriterion ModulationCriterion Modulation

nn Also tested the effect of seeing the contextAlso tested the effect of seeing the contextslightly before the targetslightly before the target

New ParadigmNew Paradigm

nn 60 participants60 participantsnn Cue to control Cue to control attentional attentional orientationorientation

1000ms

Cue

New ParadigmNew Paradigm

nn Picture stimulusPicture stimulus•• Centrally placed targetCentrally placed target•• Four objects placed around target to form contextFour objects placed around target to form context

In-context Out of context

New ParadigmNew Paradigm

nn SOA of context to target was manipulated soSOA of context to target was manipulated socontext was seen:context was seen:•• Simultaneously with target (SOA = 0ms)Simultaneously with target (SOA = 0ms)•• Or before target (SOA = -52ms & -104ms)Or before target (SOA = -52ms & -104ms)

nn Display time was 52ms for all context andDisplay time was 52ms for all context andtarget imagestarget images

1000ms

Cue

52ms

Picture Stimulus (SOA = 0ms)

1000ms

Cue

52ms52ms

52ms

Picture Stimulus (SOA -104ms)

New ParadigmNew Paradigm

nn Target offset was masked (1000ms)Target offset was masked (1000ms)nn Six alternative forced choice response (errorSix alternative forced choice response (error

rates)rates)•• Allows differentiation between number of perceptualAllows differentiation between number of perceptual

errors and number of semantic errorserrors and number of semantic errors

1000ms

Cue

52ms

Picture Stimulus

1000ms

Mask

Self-Paced

6AFC

New ParadigmNew Paradigm

nn Six alternative forced choice responseSix alternative forced choice response1.1. TargetTarget e.g. Cardse.g. Cards2.2. Physically similar to targetPhysically similar to target e.g. Paper Fane.g. Paper Fan3.3. Semantically related to contextSemantically related to context e.g. Roulette wheel (in)e.g. Roulette wheel (in)

e.g. Banana (out)e.g. Banana (out)

•• Possible guessing strategyPossible guessing strategynn Participant can deduce contextParticipant can deduce contextnn Guess has 1:2 chance for in-context trials but 1:3Guess has 1:2 chance for in-context trials but 1:3

chance for out of context trialschance for out of context trials

New ParadigmNew Paradigm

nn Six alternative forced choice responseSix alternative forced choice response1.1. TargetTarget e.g. Cardse.g. Cards2.2. Physically similar to targetPhysically similar to target e.g. Paper Fane.g. Paper Fan3.3. Semantically related to contextSemantically related to context e.g. Roulette wheel (in)e.g. Roulette wheel (in)

e.g. Banana (out)e.g. Banana (out)

4.4. Physically similar to choice 3Physically similar to choice 3 e.g. Tyre (in)e.g. Tyre (in)e.g. Horn (out)e.g. Horn (out)

5.5. Semantically related to choice 2Semantically related to choice 2 e.g. Chopsticks (out)e.g. Chopsticks (out)No relationship No relationship e.g. Mobile phone (in)e.g. Mobile phone (in)

6.6. Physically similar to choice 5Physically similar to choice 5 e.g. Straws (out)e.g. Straws (out)e.g. Calculator (in)e.g. Calculator (in)

Guessing correction 1Guessing correction 1

nn Picking one of two contextually relatedPicking one of two contextually relatedchoices?choices?

In-contextIn-context Out of contextOut of contextTarget:Target: Cards Cards –– G1 G1 CardsCardsPhyMatchPhyMatch:: Paper FanPaper Fan Paper Fan Paper Fan –– G1 G1ConMatchConMatch:: Roulette Wheel Roulette Wheel –– G1 G1 BananaBananaEType3:EType3: TyreTyre HornHornEType4:EType4: Mobile PhoneMobile Phone Chopsticks Chopsticks –– G1 G1EType5:EType5: CalculatorCalculator StrawsStraws

G1 = EType4[Out] G1 = EType4[Out] –– (EType3[Out] + EType5[Out])/2 (EType3[Out] + EType5[Out])/2

PerceptuallySimilar Pairs

SemanticallyRelated Pairs

Guessing correction 2Guessing correction 2

nn Guessing based on context alone? (ResponseGuessing based on context alone? (Responsebias correction)bias correction)

In-contextIn-context Out of contextOut of contextTarget:Target: Cards Cards –– G2/2 G2/2 CardsCardsPhyMatchPhyMatch:: Paper FanPaper Fan Paper FanPaper FanConMatchConMatch:: Roulette Wheel Roulette Wheel –– G2/2 G2/2 Banana Banana –– G2 G2EType3:EType3: TyreTyre HornHornEType4:EType4: Mobile PhoneMobile Phone ChopsticksChopsticksEType5:EType5: CalculatorCalculator StrawsStraws

G2 = G2 = ConMatchConMatch[Out] [Out] –– (EType3[Out] + EType5[Out])/2 (EType3[Out] + EType5[Out])/2

PerceptuallySimilar Pairs

SemanticallyRelated Pairs

Results Results –– Error Rates Error Rates

Repeated measures ANOVARepeated measures ANOVAnn Main effect of contextMain effect of context

•• Uncorrected:Uncorrected: F(1, 48) = 20.979, p < 0.01F(1, 48) = 20.979, p < 0.01•• Corrected:Corrected: F(1, 48) = 8.407, p < 0.01F(1, 48) = 8.407, p < 0.01

nn Main effect of SOAMain effect of SOA•• Uncorrected:Uncorrected: F(2, 96) = 60.874, p < 0.01F(2, 96) = 60.874, p < 0.01•• Corrected:Corrected: F(2, 96) = 3.980, p < 0.05F(2, 96) = 3.980, p < 0.05

Results Results –– Error Rates Error Rates

nn Context x SOA interactionContext x SOA interaction•• Uncorrected:Uncorrected: F(2, 96) = 5.888, p < 0.01F(2, 96) = 5.888, p < 0.01•• Corrected:Corrected: not significantnot significant

Uncorrected line graph data Corrected line graph data

Uncorrected Context X SOA

20

25

30

35

40

45

50

In OutContext

Erro

r Rat

e (%

)

0 ms

-52 ms

-104 ms

Corrected Context X SOA

20

25

30

35

40

45

50

In OutContext

Erro

r Rat

e (%

)0 ms

-52 ms

-104 ms

Results Results –– Broken down by Error TypeBroken down by Error Type

Repeated measures ANOVARepeated measures ANOVAnn Main effect of error typeMain effect of error type

•• Uncorrected:Uncorrected: F(4, 192) = 38.177, p < 0.01F(4, 192) = 38.177, p < 0.01•• Corrected:Corrected: F(4, 192) = 61.381, p < 0.01F(4, 192) = 61.381, p < 0.01

nn SOA x error type interactionSOA x error type interaction•• Uncorrected: Uncorrected: F(8, 384) = 5.926, p < 0.01F(8, 384) = 5.926, p < 0.01•• Corrected:Corrected: not significantnot significant

nn Planned comparisons: (corrected)Planned comparisons: (corrected)•• Perceptual errors: Perceptual errors: F(1, 48) = 4.994, p < 0.05F(1, 48) = 4.994, p < 0.05•• Semantic errors:Semantic errors: not significantnot significant

Results Results –– Broken down by Error TypeBroken down by Error Type

nn Effect of response bias correction onEffect of response bias correction onsemantic errorssemantic errors

Corrected SOA x Error Type

0

2

4

6

8

10

12

14

0 ms -52 ms -104 msSOA

PerceptualSemantic345

Error Type

Uncorrected SOA x Error Type

0

2

4

6

8

10

12

14

0 ms -52 ms -104 msSOA

PerceptualSemantic345

Error Type

Results Results –– Broken down by Error TypeBroken down by Error Type

nn Fewer perceptual errors in in-context conditionFewer perceptual errors in in-context condition

Corrected Context x Error Type

02468

101214

In OutContext

Erro

r Rat

e (%

)

PerceptualSemantic345

ConclusionsConclusions

nn Eliminating response bias does removeEliminating response bias does removesome of the context effectsome of the context effect

nn A context consistent to the target alsoA context consistent to the target alsoincreases sensitivity in recognition tasksincreases sensitivity in recognition tasks

nn Combination of perceptual analysis andCombination of perceptual analysis andcontextual information reduces perceptualcontextual information reduces perceptualerrorserrors

nn Consistent with Criterion Modulation notConsistent with Criterion Modulation notFunctional IsolationFunctional Isolation