Task combination and divided attention
Just as there is controversy over the nature of attentional processing in selective attention tasks, psychologists hold a variety of views about the best explanation for human performance in divided attention conditions. When two tasks need to be done at the same time, is attention shared? Are there different attentional mechanisms responsible for different tasks? Different modalities? But what, exactly, is it that we do “at the same time”? The classic psychological refractory period (PRP) studies by Welford (1952) looked at overlapping tasks in which one and then another simple stimulus was presented for speeded response. Other tasks, some of which we shall meet here, require subjects to do two tasks at the same time, but on a trial by trial basis; e.g. Posner and Boies (1971). Sometimes, experiments involve the continuous performance of two, quite lengthy, ongoing tasks; e.g. Allport, Antonis, and Reynolds (1972). It is possible that these different tasks make quite different demands on the attentional system. Pashler (1993) reviewed dual-task performance and examined dual-task interference over a wide variety of experimental paradigms.