grange et al. (durham eps, 2016)

The Effect of Episodic Retrieval on Inhibition in Task Switching

Jim Grange, Agnieszka Kowalczyk, & Rory O’Loughlin

A Problem of Control

• Humans live in a rich, multi-task environment

• Goal-directed behaviour requires selecting the most relevant stimulus to act upon


• Stimulus selection is only half the battle:– Stimuli are often multivalent


• When stimuli are multivalent, we must be able to select the relevant task to perform

• We must also be able to maintain that operation once selected so task-irrelevant operations do not intrude


• We must also be able to maintain that task once selected so task-irrelevant intrusions do not occur


• We must also be able to switch away from this task when our goals change

Task Switching

Grange & Houghton (2009, 2010); Houghton et al. (2009)

How is Task Switching Achieved?

• A possible solution:

– Activate task-relevant representations when they are required

– Inhibit task-irrelevant representations when they are no longer required

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”


• Why is this effect important?

– Can be used to investigate inhibition using different approaches:• Clinical• Neuropsychological• Neuroscience • Individual Differences


• Why is this effect important?

– Many “inhibition” effects can be explained without appeal to inhibitory mechanisms• e.g., negative priming, Stroop performance

– N-2 repetition cost is—to date—robust against these alternative explanations

Episodic Retrieval Account

• A key non-inhibitory account that can explain a lot of “inhibitory-type” effects

• Automatic cue-based retrieval of episodic traces of previous task experience

– Retrieval facilitates performance if it matches current task demands

– Retrieval interferes with performance if it mis-matches current task demands

“Bottom Left!”

Time

MATCH!

“Bottom Left!”

Time

MISMATCH!

Episodic Retrieval Account

• Explains the n-2 repetition cost by interference during episodic retrieval rather than inhibition

Time

EpisodicMatch

N-2 Repetition Facilitation

Episodic Mismatch


N-2 Repetition Cost


Episodic Retrieval Prediction

Mayr’s (2002) Results

Error bars denote +/- 1 SE

Mayr (2002)

• Episodic retrieval cannot explain n-2 repetition cost in task switching– Remains a strong marker of inhibition

• It is not clear, though, whether episodic retrieval has any modulatory effect

Mayr (2002)

• Numerical trend for smaller costs for episodic matches

• F(1, 38) = 1.3, p=.26

• Can’t accept a null!


Mayr (2002)

• Bayesian analysis of this interaction (BF01 = 0.315) suggests null ~ 3 times more likely

• This only provides “anecdotal” support for null (Schoenbrodt et al., 2016)


The Present Study: Experiment 1

The Present Study

• Replicate key aspects of Mayr’s (2002) design

• Used sequential Bayesian analysis to collect compelling data

– We only stopped data collection once we had “substantial” support for one hypothesis over the other

– (i.e., whether episodic retrieval does or does not modulate the n-2 repetition cost)

Sequential Bayesian Analysis

• Conduct Bayesian t-test after every participant– N-2 repetition cost (resp. rep.) Vs. – N-2 repetition cost (resp. switch)

• Bayes Factor– Degree of support for one model (i.e., hypothesis)

compared to another model, given the data observed– BF10 of 10 means alternative is 10 times more likely

than null, given the data– BF10 of 0.1 means null is 10 times more likely than

alternative, given the data

Sequential Bayesian Analysis

• Stop data collection when the Bayes factor is either:

– Greater than 6 (strong support for alternative)

– Less than 1/6 (strong support for null)

Method

• N = 76• Replication of Mayr’s

design• 4 blocks of 120 trials• Task chosen randomly

(no repetitions)• Stimulus location

chosen randomly

Results• Sequence: F(1, 75) = 94.14, p < .001, η2

G = .018

• Response Rep.:F(1, 75) = 18.21, p < .001, η2

G = .004

• Interaction: F(1, 75) = 9.60, p < .01, η2

G = .001


Results• Bayes Factor:• BF10 = 9.97

• Model of different n-2 repetition costs for response repetition and switch is 10 times more likely than a null model


Discussion

• N-2 repetition cost is modulated by episodic retrieval

– When retrieval parameters match current task demands, the n-2 repetition cost is reduced

– Almost halves the cost (!)– Important if we wish to use this cost as an

individual difference marker of inhibition

Experiment 2

Method

• Manipulated cue–task complexity

• Arrow cues provide bottom-up support for response selection

• Shape cues have no pre-experimental association with tasks

Arrow Cues Shape Cues

Method

Arrow Cues• Less reliance on

working memory representations

• Less benefit / interference from episodic retrieval

• Reduced episodic retrieval effect


Method

Shape Cues• Greater reliance on

working memory representations

• More benefit / interference from episodic retrieval

• Increased episodic retrieval effect


Method

• Stopping rule same as before, but test is on 3-way interaction

• Currently have 17 subjects– Not ready to stop, so…

• …data are thus preliminary…

30ms

132ms

3ms

–52ms

3-way Interaction: F(1, 16) = 5.61, p = .03, η2G = .009



Bayes Factor (interaction vs. 2 main effects model) =

10.93

Discussion

• Episodic retrieval effects larger with more abstract cues

– Greater reliance on WM representations– More interaction with retrieved episodic traces

Discussion

• No evidence for inhibition when episodic retrieval matches current task demands– 3ms for Arrow cues– NEGATIVE 52ms for Shape cues (i.e., positive

priming)

• This data set currently matches prediction of a pure episodic retrieval account of the n-2 repetition cost

Predicted vs. Observed


Conclusions

• We have provided evidence for (at least) a modulatory role of episodic retrieval during task switching

• When retrieval matches current task demands:– Reduces the n-2 repetition cost (Exp. 1)– Introduces an n-2 repetition benefit (Exp. 2)

Conclusions

• The n–2 repetition cost in task switching is (at least) a contaminated measure– Task-specific inhibition plus– Episodic interference / facilitation

• Researchers needs to be cognisant of this issue when using this effect as a “pure” measure of inhibition

Thank You!

A copy of these slides will be available on our lab’s website:

www.jimgrange.wordpress.com

http://www.jimgrange.wordpress.com/

Stopping Rule in Action

Prior Robustness Check

grange et al. (durham eps, 2016)

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