ABSTRACT
The wide setting of the zoom lens and the breakthrough of the unattended are instances of divided attention in the sense of distraction from focusing. In this chapter, the perspective shifts from distraction to performance of more than one task at once, which is related to the issue of mental workload. Here, the notion of a human being as a limited-capacity processor has its deepest roots. Hence, the question is how well the capacity concept does in its homeland. Besides limited-capacity theory, the notion of a central executive controller is considered. How freely may capacity be distributed among different tasks? Limited capacity and central executive notions are confronted with more recent connectionist-inspired approaches that have “interference” as their password and claim to do without a central executive. How much capacity is consumed by a particular task? The usual answer is that this depends on practice and automation. Because the issue of automaticity pervades theorizing on dual-task performance, the chapter starts with a summary on automaticity and the orienting reaction, both of which are strongly related. This is followed by a review on dual-task performance proper. The final part of the chapter addresses a widely studied microcase of dual-task performance, namely, the psychological refractory period (PRP). It is a microcase because the dual task is limited to two independent discrete responses to two stimuli that are presented in rapid succession. The PRP paradigm has a special status because the findings there deviate considerably from those obtained when performing a more complex dual task that directly bears on the issue of generalization from the simple to the more complex.
