Does Secondary Task Measure Outcome Conflict or Resource Allocation?

Abstract

The secondary task technique was used to test two alternative explanations of dual task decrement: outcome conflict and resource allocation. Subjects time-shared a continuous tracking task and a discrete Sternberg memory task. The memory probes were presented under three temporal predictability conditions. Dual task performance decrements in both the tracking and memory tasks suggested that the two tasks competed for some common resources, processes, or mechanisms. Although performance decrements were consistent with both the outcome conflict and resource allocation explanations, the two explanations propose different mechanisms by which the primary task could be protected from interference from the concurrent secondary task. The primary task performance could be protected by resource allocation or by strategic sequencing of the processing of the two tasks in order to avoid outcome conflict. In addition to examining the global trial means, moment-by-moment tracking error time-locked to the memory probe was also analyzed. There was little indication that the primary task was protected by resequencing of the processing of the two tasks. This together with the suggestion that predictable memory probes led to better protected primary task performance than less predictable memory probes lend support for the resource explanation.