Modelling response selection in task switching: Testing the contingent encoding assumption

Abstract

The contingent encoding assumption is the idea that response selection in task-switching situations does not begin until the cue and the target have both been encoded. The authors tested the assumption by manipulating response congruency, stimulus order, and stimulus onset asynchrony (SOA) in two experiments. They found evidence of response selection prior to cue encoding for congruent targets with target–cue order at a long SOA, indicating that the contingent encoding assumption is invalid. The authors describe how contingent encoding can be removed from an existing task-switching model by introducing baseline evidence—task-neutral evidence that serves as a baseline for response selection prior to stimulus encoding. Simulations revealed that the modified model could reproduce the full pattern of response time data and generate responses prior to cue encoding. The authors conclude by discussing directions for further model development.

Keywords:

• Task switching
• Response selection
• Response congruency
• Stimulus order
• Cognitive modelling

This research was based on part of the first author's doctoral dissertation supervised by the second author.

FUNDING

Funding was provided by the National Institute of Mental Health [grant number R01-MH073878-01] to the second author.

Notes

¹Three of the 24 subjects in Experiment 1 and two of the 24 subjects in Experiment 2 made no early responses on congruent trials with target–cue order at an SOA of 800 ms. However, these subjects had mean RTs on congruent trials at an SOA of 0 ms that were longer than their respective group means, raising the possibility that the absence of early responding at the longer SOA might have been due to slow responding in general.

²Appendix C shows that the retrieval probability for the correct response in Scenario 6 is higher than that in Scenario 5. Higher retrieval probabilities lead to shorter RTs and lower ERs. The difference in retrieval probability between congruent and incongruent targets is what allowed our previous model of compound cue retrieval to produce the response congruency effect.

³The subscripts c, t, a, and u stand for cue, target, associated, and unassociated, respectively.