The microstructure of dual task interaction. 3. Incompatibility and attention switching

This report is the third in a series of reports concerned with close analysis of a dual task situation in which a five-choice serial task is combined with an auditory--verbal response task. A situation is described in which 'incompatibility' is incorporated into the five-choice task in order to increase the information processing load and thus explore the effect on the mechanism believed to control the microstructure of the time-sharing process. Results supported the notion that subjects were continuing to operate a sequential processing strategy in combining the two tasks. The structure of the interval generated by the occurrence of the auditory--verbal task was different in comparison with the compatible five-choice condition reported earlier, suggesting that the introduction of incompatibility causes a change in the characteristics of the time-sharing process. The structure of the interval remained organised and consistent, suggesting that the mechanism which controlled the time-sharing process was not disrupted by increased main task load and therefore was likely to involve a process which did not compete for attention space with task variables. Results also revealed an effect of the digit task response on the following two serial responses. It was suggested that these were probably best described as two independent effects: one arising from the sequential processing strategy adopted, and the other arising perhaps as a function of perception of overall task difficulty.