This study investigated how episodic retrieval modulates inhibition in task switching. The researchers replicated a previous study that found a reduced N-2 repetition cost when the previous task matched the current one compared to when it mismatched. Using sequential Bayesian analysis, they collected data until the Bayes factor provided substantial evidence that episodic retrieval does modulate the N-2 repetition cost. The results provided strong support for this alternative hypothesis over the null hypothesis. The researchers concluded that the N-2 repetition cost reflects both task-specific inhibition and episodic interference/facilitation effects.

1. The Effect of Episodic Retrieval on
Inhibition in Task Switching
Jim Grange, Agnieszka Kowalczyk, &
Rory O’Loughlin

2. A Problem of Control
• Humans live in a rich, multi-task environment
• Goal-directed behaviour requires selecting the
most relevant stimulus to act upon

3. A Problem of Control
• Stimulus selection is only half the battle:
– Stimuli are often multivalent

4. A Problem of Control
• 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

5. A Problem of Control
• We must also be able to maintain that task
once selected so task-irrelevant intrusions do
not occur

6. A Problem of Control
• We must also be able to switch away from
this task when our goals change

7. Stability-Flexibility Dilemma
• Task representations must be stable so task-
irrelevant intrusions do not occur
• Task representations must be flexible so that
they can be removed when goals change
• How is this tension resolved?
Goschke (2000)

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

9. 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

10. Inhibition in Task Switching
A B A
Time
Mayr & Keele (2000)

11. Inhibition in Task Switching
A B A
Time
Mayr & Keele (2000)

12. Inhibition in Task Switching
A B A
Time
Mayr & Keele (2000)

13. Inhibition in Task Switching
A B A
Time
Mayr & Keele (2000)

14. Inhibition in Task Switching
A B A
C B A

15. Inhibition in Task Switching
A B A
C B A
Backward Inhibition (BI) = RT(ABA) – RT(CBA)
“N–2 repetition cost”

16. Inhibition in Task Switching
• Why is this effect important?
– Provides insight into how cognitive control during
task switching is achieved

17. Inhibition in Task Switching
• Why is this effect important?
– Can be used to investigate inhibition using
different approaches:
• Clinical
• Neuropsychological
• Neuroscience
• Individual Differences

18. Inhibition in Task Switching
• 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

19. 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

20. “Bottom Left!”
Time
MATCH!

21. “Bottom Left!”
Time
MISMATCH!

22. Episodic Retrieval Account
• Explains the n-2 repetition cost by
interference during episodic retrieval rather
than inhibition
Time

26. Episodic
Match

27. N-2 Repetition
Facilitation

28. Episodic
Mismatch
N-2 Repetition
Facilitation

29. N-2 Repetition
Cost
N-2 Repetition
Facilitation

30. Episodic Retrieval Prediction

31. Mayr’s (2002) Results
Error bars denote +/- 1 SE

32. 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

33. Mayr (2002)
• Numerical trend for
smaller costs for
episodic matches
• F(1, 38) = 1.3, p=.26
• Can’t accept a null!
Error bars denote +/- 1 SE

34. 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)
Error bars denote +/- 1 SE

35. The Present Study

36. 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)

37. 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

38. 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)

39. Method
• N = 76
• Replication of Mayr’s
design
• 4 blocks of 120 trials
• Task chosen randomly
(no repetitions)
• Stimulus location
chosen randomly

40. 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
Error bars denote +/- 1 SE

41. 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
Error bars denote +/- 1 SE

42. 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 (!)

43. Conclusions
• We have provided evidence for (at least) a
modulatory role of episodic retrieval during
task switching
• The n–2 repetition cost in task switching is (at
least) a contaminated measure
– Task-specific inhibition plus
– Episodic interference / facilitation

44. Conclusions
• Researchers needs to be cognisant of this
issue when using this effect as a “pure”
measure of inhibition
– Used to investigate inhibition using different
approaches:
• Clinical
• Neuropsychological
• Neuroscience
• Individual Differences

45. Thank You!
A copy of these slides will be available
on our lab’s website:
www.jimgrange.wordpress.com

46. Prior Robustness Check

47. Progression of Bayes Factor