Effects of age and task similarity on dual-task performance.

When a dual tracking task consisting of two incoherent (uncorrelated) subtasks is partly integrated, such that it is characterized by incompatibility of similarity, or when axis similarity of subtasks is high, it may be difficult to map subtask stimuli to the proper responses. Especially for older adults, an increase in mapping demands may be a source of confusion (cross talk). In the present experiment this issue was addressed with a dual task consisting of two unrelated one-dimensional compensatory tracking tasks with position dynamics. Task performance was measured in terms of root mean square tracking error and cross-axial correlations. Tracking error data were consistent with the hypothesis that older subjects are penalized when there is incompatibility between control and display integration. In general, negative effects of incompatibility of integrality were the greatest when partial integration involved integration of the response component. Both performance measures indicated that with increasing incoherent similarity, task performance of the old subjects was more hampered than was that of their young counterparts.