Response strategies in manual control tasks

Man´s ability to handle two or more channels of information which overlap in time has been a subject of considerable recent interest. This paper reviews a series of experiments involving performance on two overlapping tasks. The primary task, in most instances, was the pursuit tracking of step-function inputs. Secondary tasks which were varied to determine those conditions which would interfere with tracking performance, typically involved verbal response to a second signal source. Among the more significant results is evidence that a principal source of interference is the response selection (as distinguished from the response execution) requirements of the second task. It appears that the limitation on two channel processing may be a limit in decision-making capabilities, and that the relevant decisions are those involved in selecting among alternative responses. The findings appear to hold for rather different tasks and are not limited to manual control (tracking) operations.