EXPRESS: Exploring 'phasic' vs. 'tonic' accounts of the effect of switch probability on the auditory attention switch cost.

Abstract

Task-switching experiments have shown that the 'switch cost' (poorer performance for task switches than for repetitions) is smaller when the probability of a switch is high (e.g., 0.75) than when it is low (e.g., 0.25). Some theoretical accounts explain this effect in terms of top-down control deployed in advance of the task cue ('pre-cue reconfiguration'). We tested such accounts by manipulating the time available before the onset of the cue (the response-cue interval, RCI), reasoning that top-down pre-cue reconfiguration requires time and therefore its effect should increase with RCI. Participants heard a man and a woman simultaneously speaking number words and categorised the number (<5 vs. >5) spoken by the voice specified by a pictorial gender-related cue presented at an RCI of 100 ms or 2200 ms. The target voice switched with a probability of 0.25 or 0.75 (in separate sessions). In Experiment 1 RTs revealed a large effect of switch probability on the switch cost in the short RCI, which did not increase in the long RCI. Errors hinted at such an increase, but it did not receive clear statistical support and was disconfirmed by a direct and better powered replication in Experiment 2, which fully confirmed the RT pattern from Experiment 1. Thus, the effect of switch probability on the switch cost required little/no time following the response to emerge - it was already at full magnitude at a short RCI - challenging accounts that assume 'phasic' deployment of top-down task-set control in advance of the cue.