Rethinking volitional control over task choice in multitask environments: use of a stimulus set selection strategy in voluntary task switching

Abstract

Under conditions of volitional control in multitask environments, subjects may engage in a variety of strategies to guide task selection. The current research examines whether subjects may sometimes use a top-down control strategy of selecting a task-irrelevant stimulus dimension, such as location, to guide task selection. We term this approach a stimulus set selection strategy. Using a voluntary task switching procedure, subjects voluntarily switched between categorizing letter and number stimuli that appeared in two, four, or eight possible target locations. Effects of stimulus availability, manipulated by varying the stimulus onset asynchrony between the two target stimuli, and location repetition were analysed to assess the use of a stimulus set selection strategy. Considered across position condition, Experiment 1 showed effects of both stimulus availability and location repetition on task choice suggesting that only in the 2-position condition, where selection based on location always results in a target at the selected location, subjects may have been using a stimulus set selection strategy on some trials. Experiment 2 replicated and extended these findings in a visually more cluttered environment. These results indicate that, contrary to current models of task selection in voluntary task switching, the top-down control of task selection may occur in the absence of the formation of an intention to perform a particular task.

Keywords: Cognitive control; Task selection; Volitional behaviour; Voluntary task switching.

Figure 1

A) Example trial line depicting displays in a sample trial for the 4-position condition. Displays not shown to scale. B) Examples of the final target displays for the 2-, 4-, and 8-position conditions from Experiment 1 and for Experiment 2.

Figure 2

Probability of performing the task associated with stimulus 1, p(S1), as a function of position condition and SOA for Experiment1 (panel A) and Experiment 2 (panel B). Error bars represent 95% confidence intervals calculated based on the standard error of the mean for each cell in the design.

Figure 3

Probability of performing the task associated with the stimulus in the location repeated from trial n-1, p(Location Repetition), as a function of position condition and stimulus order (S1 or S2) for Experiment1 (panel A) and Experiment 2 (panel B). Error bars represent 95% confidence intervals calculated based on the standard error of the mean for each cell in the design.