Characterizing attentional resources.

Other studies have found that it is easier to divide attention when messages can be discriminated on the basis of stimulus and response features. The present study extended these results and explored whether dual-task performance is a function of similarity of central processing and, more specifically, the semantic similarity of the competing messages. In a dichotic listening task, subjects detected targets in concurrent messages that either differed semantically and required different central processing (the mixed condition) or were semantically similar and required similar central processing (the same condition). Three criteria are developed to determine whether the tasks in the mixed condition call upon distinct resources. The results are discussed in terms of three metaphors for resources: fuel, structure, and skills.