Task Dependent Differences and Individual Differences in Dual Task Performance

The methodological issues involved in demonstrating the existence of a time-sharing ability are outlined. A survey of relevant experimental literature indicates that, while there is some evidence for a task specific time-sharing ability, there appears to be little for a more general A-factor of attention of dual task performance ability. An experiment is then described in which 40 subjects performed 4 tasks singly and in various pairwise combinations. The tasks, tracking, spatial judgments, digit classification and auditory memory, were selected to systematically load different stages of information processing. The patterns of task interference observed, conformed to predictions of structure specific capacity theories of attention, with structures defined by processing stages, processing modalities and cerebral hemispheres. Confirming previous research, little evidence was provided for a general time-sharing ability. More specific abilities were however suggested by the data to relate to visual scanning, and automation of auditory memory store.