On attentional control as a source of residual shift costs: Evidence from two-component task shifts

It is widely assumed that supervisory or attentional control plays a role o nly in the preparatory reconfiguration of the mental system in task shiftin g. The well-known fact that residual shift costs are still present even aft er extensive preparation is usually attributed to passive mechanisms such a s cross talk. The authors question this view and suggest that attentional c ontrol is also responsible for residual shift costs. The authors hypothesiz e that, under shift conditions, tasks are executed in a controlled mode to guarantee reliable performance. Consequently, the control of 2 task compone nts should require more resources than the control of only 1. A series of 4 experiments with 2-component tasks was conducted to test this hypothesis. As expected, more residual shift costs were observed when 2 components rath er than 1 varied across trials. Interference effects and sequential effects could not account for these results.