a common principle of conflict resolution in single and dual-task settings

vrije Universiteit amsterdamCognitieve Psychologie

A Common Principle of Conflict Resolution in Single and Dual-Task

Settings

Sander A. LosVrije Universiteit, Amsterdam

The sign of orro

1.Zorro appears at the critical moment2.Zorro’s dual strike

1.Zorro appears at the critical moment

Variable-foreperiod design

S1 S2 R

Foreperiod (FP) RT

Critical moments

Imperative moment

Foreperiod on trial n (s)

0 2 4 6 8 10 12 14 16

(Zahn et al., 1963)

0 2 4 6 8 10 12 14 16

FPn - 1: 1.0 s

FPn - 1: 2.0 s

FPn - 1: 4.0 s

FPn - 1: 7.0 s

FPn - 1: 15.0 s

Accounts

Activationon trial n

Inhibitionon trial n - 1

Imperative momenton trial n - 1

Activation view Inhibition view

Suppose: S2 appeared at the 2nd critical moment on trial n - 1

S2 on trial n - 1time

Activation view: re-preparation

=> Expect S2 at 2nd critical moment on trial n

Expectancy trial n time

S2 on trial ntime

• S2 occurs before expected moment: RT = long

S2 on trial ntime

• S2 occurs before expected moment: RT = long• S2 occurs at the expected moment: RT = short

S2 on trial ntime

• S2 occurs before expected moment: RT = long• S2 occurs at the expected moment: RT = short• S2 occurs beyond the expected moment: RT = short!

repreparation

(e.g., Niemi & Näätänen, 1981)

Critical moments

Inhibition view: Trace conditioning

SOAn vs SOAn SOAn vs Activation

ning real time

Bypassing the first critical moment:

ning real time

Bypassing the first critical moment: Extinction

ning real time

Bypassing the second critical moment:

ning real time

Bypassing the second critical moment: Extinction

ning real time

S2The imperative moment:

ning real time

The imperative moment: Reinforcement

State of conditioning prior to trial n + 1

Note: state of conditioning associated with the last critical moment remains unchanged.

Accounts

Activationon trial n

Inhibitionon trial n - 1

Activation view Inhibition view

Experiment:Probing the inhibitory process

• Go / no-go task with respect to S2 in variable FP design

• Evidence for response inhibition on no-go trials

• After a no-go trial, extinction replaces reinforcement at the imperative moment

Design

0 ms, S1

1000 ms, S1 off: start FP

Response

Conditions:1. 50% “ready” go trials

1300 or 2200 ms, S2: Go

Design

0 ms, S1

No Response

Conditions:1. 50% “ready” go trials2. 25% “ready” no-go trials

1300 or 2200 ms, S2: NoGo

Design

0 ms, S1

No Response

Conditions:1. 50% “ready” go trials2. 25% “ready” no-go trials3. 25% “relax” no-go trials

1300 or 2200 ms, S2: NoGo

PredictionsN - 1 = “ready” go: extinction only when bypassing the critical moment

FP on trail n: 1200 ms

300 1200

FP on trial n: 300 ms

300 1200

FP_n-1 vs FP_n-1

FP_n-1 vs pred_go_k: 300.00

FP on trial n - 1 (ms)

trial n - 1:go

trial n - 1:

"ready": go

PredictionsN - 1 = “ready” no-go: extinction both when bypassing the critical moment and at the imperative moment

300 1200

FP_n-1 vs FP_n-1 FP_n-1 vs pred_go_k

FP_n-1 vs pred_nogo_k_ten

trial n - 1:go

trial n - 1:

"ready": go

"ready": no-go

PredictionsN - 1 = “relax” no-go: extinction neither when bypassing the critical moment nor at the imperative moment

300 1200

FP_n-1 vs FP_n-1 FP_n-1 vs pred_go_k

FP_n-1 vs pred_nogo_k_ten

FP_n-1 vs pred_nogo_k_rel

trial n - 1:go

trial n - 1:

"ready": go

"ready": no-go

"relax": no-go

Findings

FP on trial n is long: confirms prediction

Findings

300 1200

FP_n-1 vs FP_n-1

FP_n-1 vs go_k FP_n-1 vs nogo_k_ten FP_n-1 vs nogo_k_rel

trial n - 1:go

trial n - 1:

"ready": go

"ready": no-go

"relax": no-go

FP on trial n = short: Zorro appears (... but is a bit off target)

Conclusions (1)

Consistent with the trace conditioning account, response inhibition on trial n - 1 affects RT on trial n.

Conclusions (2)

Response inhibition accounts directly for sequential effects of foreperiod.

0 2 4 6 8 10 12 14 16

FPn - 1: 1.0 s

FPn - 1: 2.0 s

FPn - 1: 4.0 s

FPn - 1: 7.0 s

FPn - 1: 15.0 s

(Zahn et al., 1963)

Conclusions (3)

Response inhibition accounts indirectly for the classical FP – RT function.

0 2 4 6 8 10 12 14 16

(Zahn et al., 1963)

Common themes in Single- and Dual-Task Control

• Switching between levels of an independent variable

• Result: asymmetric switch costs

• Involvement of inhibitory processing

2. Zorro’s dual strike

Task switch paradigm

A A B B B B A B A A …...

Nonswitch: task set on trial n = task set on trial n - 1

Switch: task set on trial n task set on trial n - 1

Participants apply task sets A and B on different trials, as specified by a preceding cue:

Typical findings:• Switch costs: RTnonswitch < RTswitch• Residual switch costs: switch costs when the cue-target interval is relatively long (e.g., exceeding 1,000 ms).

Task switch paradigm

Two questions:

1. Origin of switch costs: where do switch costs come from?

2. Control of switch costs: Can switch costs be reduced to zero by endogenous means during a long preparatory interval?

Origin of Switch Costs

Mayr & Keele (2000): Three task sets: A, B, C

C B AA B A

Finding: RTCBA < RTABA

“Backward inhibition”: on trial n - 1 participants inhibit the task set performed on trial n - 2, leading to costs on trial n if the task set on trial n is the same as on trial n - 2.

Origin of Switch Costs

When does backward inhibition come into play?

1. During the Cue - Target interval

2. After the onset of the target stimulus

switch costs are caused by endogenous task set preparation on trial n - 1.

switch costs are caused by task set competition on trial n - 1.

Schuch & Koch, 2003

Combined task switch, go / no-go design. A tone was presented simultaneously with the target:• High tone (75%): Go: Apply task set• Low tone (25%): No-go: Don’t apply task set

Schuch & Koch, 2003

R n – 1

Tone + Target

600 ms

100 or 1,000 ms

Cue: Square (odd / even) ordiamond (higher / lower 5)CTI: 100 or 1,000 msTarget: 1, 2, 3, 4, 6, 7, 8, 9Tone: high (go, 75%)or low (no-go, 25%)

Schuch & Koch, 2003

Trial Type

repeat switch

Responsen - 1: go

Responsen - 1: no-go

Main Finding:Switch costs were only observed after a go trial, not after a no-go trial.

Conclusion:Switch costs require task-set application. Switch costs result from task-set competition.

Schuch & Koch, 2003

Problem:Given that no task-set competition occurred on no-go trials, why was RT relatively long after a no-go trial?

Trial Type

repeat switch

Responsen - 1: go, observed

Responsen - 1: no-go, observed

Responsen - 1: no-go, predicted

Proposed solution:A no-gon – 1 trial prolongs another stage (or other stages) on trial n.

Schuch & Koch, 2003

Response selection Stage X

Trial Type Responsen - 1

Present study

Response selection Stage X

Trial Type Responsen - 1Factor

Present study

Response selectionDecision whether to respond

Trial Type Responsen - 1TTI

Hypothesis: stage X represents a decision-whether-to-respond stage, selectively influenced by the Tone – Target Interval (TTI).

Design

Odd – Even2

Rn - 1

Odd - Even Target (+ Tone)

Cue (+ Tone)

600 ms

1,000 ms

Cue: odd - even or high - lowTTI: 0 or 1,000 msTarget: 1, 2, 3, 4, 6, 7, 8, 9Tone: high (go, 75%)or low (no-go, 25%)

Results

(Los & Van der Burg, in preparation)

Trial Type

repeat switch

go 0 go 1,000

Responsen - 1 TTIn (ms)

• large effect of TTI

Results

Trial Type

repeat switch

go 0 go 1,000 no-go 0

• short TTI, responsen - 1: no-go - no switch costs - RT is relatively long

Results

Trial Type

repeat switch

go 0 go 1,000 no-go 0 no-go 1,000

• short TTI, responsen - 1: no-go - no switch costs - RT is relatively long

• long TTI , responsen - 1: no-go - no switch costs - RT is relatively fast

Zorro’s dual strike…..!?

Conclusions

Response selectionDecision whetherto respond

Trial Type Responsen - 1 TTI

1. Confirmation the additional stage hypothesis

Conclusions

Response selectionDecision whetherto respond

Trial Type Responsen - 1 TTI

1. Confirmation the additional stage hypothesis2. Residual switch costs are caused by task set competition

General Conclusions

• Common principles may govern task control in single and dual-task settings.

• inhibitory control is exerted whenever conflicting responses are simultaneously activated.

• consequences of inhibition carry over from one trial to the next.

The sign of orro

Thank you!

Results

Conclusions

Response selection

“whether”decision

Trial Type

Responsen - 1

1. Confirmation the additional stage hypothesis.

TTIn - 1

Motorprocessing

Conclusions

Response selection

“whether”decision

Trial Type

Responsen - 1

1. Confirmation the additional stage hypothesis.2. Switch costs are caused by task set competition

TTIn - 1

Motorprocessing

a common principle of conflict resolution in single and dual-task settings

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