eps london (2012)

The Effect of Task-Relevant andIrrelevant Verbalisations

on Inhibition in Task Switching

James A. Grange & Justine Carine

Cognitive Inhibition

“...the stopping or overriding of a mental process, in whole or in part, with or without intention.”– MacLeod (2007)

Houghton et al. (2009)

Inhibition in Task Switching

A B A

Time

Mayr & Keele (2000)


A B AC B A


A B AC B A

Backward Inhibition (BI) = RT(ABA) – RT(CBA)“N–2 repetition cost”

What is Inhibited?

• Mayr & Keele (2000) originally suggested the task-set as a whole is inhibited– Scatter-gun approach

• More parsimonious to suggest inhibition is selective– Thus targeting interference directly

• Several components of trial structure can generate interference– Cue, stimulus, response selection/execution


• Word cues verbally described the characteristic of the target to search for

• Participants must generate an endogenous representation of target


• Iconic cues visually described the characteristic of the target to search for

• Environment provides bottom-up support of target

selection as cue provides allessential information for taskperformance


• Abstract cues totally unrelated to characteristic of the target to search for

• Environment provides no support for target selection

• More processing required in WM


• Modulation of inhibition cannot be due to response- or stimulus processes– Response mappings did not change throughout

the experiment– Stimulus display did not change


Error bars denote +/- 1 Standard Error around the mean

What is Inhibited?

• Results suggest cue-related processes affect inhibition– Simpler cues provide exogenous support for task

preparation– Greater preparation leads to less observable

inhibition?

• Relatively underspecified area of the literature

Cumulative Distribution Functions

• Provide novel investigation of effects of preparation

• CDFs provide overview of an effect across the entire RT distribution – Rank participant’s RTs for each condition from

fastest to slowest– Calculate percentile cut-off points for each

condition separately– Average these points across participants and plot

Cumulative Distribution Functions

Effects of Preparation

Grange & Houghton (2011) – Psych. Bull. & Review.

Purpose of Experiments

• Can task-specific preparation reduce observable inhibition?

• Two approaches:– Disrupt preparation via articulatory suppression

(Experiment 1)– Encourage preparation via task-relevant

verbalisations (Experiment 2)

Experiment 1 - Introduction

• Relationship between verbalisation and behavioural-control functions well established (Vygotsky, 1962)

• Good evidence that verbal representations required in task switching (Saeki & Saito, 2004a, 2004b, in press)

“SHADED”

Experiment 1 – Introduction

• Articulatory suppression (AS) disrupts sub-vocal task preparation– If task preparation involves forming verbal

representations, AS should interfere with this• Control condition of foot-tapping – Secondary task that involves no verbal component

• Prediction: greater n-2 repetition cost with AS

Experiment 1 - Method• Used abstract cues of Houghton

et al. (2009)– N = 16– Fully repeated measures– 326 trials per verbalisation

condition

• Articulatory Suppression condition required overt verbalisation of “Blah” at 2Hz.

• Foot Tapping condition required tap of dominant foot at 2Hz.

Experiment 1 - Results

• Interaction not significant (p>.58)

• Bayesian t-test shows the null is 4.56 times more likely than the experimental hypothesis

Error bars denote +/- 1 SE around the mean

37ms

23ms


Articulatory Suppression Foot Tapping

Experiment 1 - Discussion

• Suppression slowed RTs– Demonstrates AS is having an adverse effect

• No influence of AS on observable cost of inhibition– Interfering with verbal representations does not

affect inhibition• Data quite noisy– Quite slow overall RT (~800-900ms)– large variance


• Instead of disrupting verbal representations, Experiment 2 sought to encourage them

• Two conditions: Relevant verbalisations & irrelevant verbalisations


• Instead of disrupting verbal representations, E2 sought to encourage them


“Square” “Triangle” “Octagon”


• Instead of disrupting verbal representations, E2 sought to encourage them


“Shaded” “Bordered” “Angled”

Experiment 2 - Method

– N = 29– Fully repeated measures– 326 trials per verbalisation condition

“Bordered” “Shaded” “Angled”

1,000ms


• Interaction not significant (p>.57)

• Bayesian t-test shows the null is 5.98 times more likely than the experimental hypothesis

Error bars denote +/- 1 SE around the mean

20ms

13ms

Irrelevant Verbalisations Relevant Verbalisations


Irrelevant Verbalisations Relevant verbalisations


• Relevant verbalisations speeded performance– Encouraging relevant verbalisation aids

performance• No significant influence on observable

inhibition– Either mean RT or using CDF analysis

• Both experiments show trend in the predicted direction


37ms

23ms

20ms

13ms

Irrelevant Verbalisations Relevant Verbalisations

General Discussion• A quandary...– Inhibition absent from fast end (prepared?) of RT

distribution– Task relevant verbalisations speed RT– Articulatory Suppression slows RT– But neither affect observable inhibition

• Perhaps absence of inhibition at faster RTs not due to preparation?– Models of choice RT may suggest otherwise...– Thanks to Darryl Schneider (personal communication)

for highlighting this possibility!

General DiscussionRatcliff Diffusion Model

General DiscussionV (Drift Rate) a (Response Caution)

Ter (Non-decision time)

General Discussion

Simulated Data

What Affects Drift Rate?

• Task difficulty• Stimulus quality• Familiarity• Stimulus frequency...

• Advanced preparation of task performance?

Thank you. Any Questions (or

suggestions!)?

www.cognitivecontrol.co.uk

http://www.cognitivecontrol.co.uk/

eps london (2012)

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