System response time and readiness for task execution - The optimum duration of inter-task delays

In several studies of computer work, system response times (SRTs) that occurred between independent (sub)tasks were observed to influence the users' performance, satisfaction or physiological state. SRTs classified as either 'long' or 'short' resulted in performance decrement and an increase in symptoms of strain. Hence, an optimum duration of inter-task SRTs can be assumed that will enable the users to achieve a perfect readiness for task execution. However, this assumption has not yet been studied systematically, observing the same subjects working on the same tasks under SRTs of various durations. In the present experiment 42 subjects were studied during inspection of artificial written material. With reference to the results of earlier studies, three SRT duration conditions (short = 1 s, medium = 5 s and long = 9 s) were applied in a balanced repeated measures design. Subjects were exposed to each condition for 10 min. Dependent measures were parameters of performance speed and accuracy, with blood pressure, heart rate and skin conductance as physiological variables, and various indicators of the subjective state. A poor performance and an increased cardiovascular activity were obtained under short SRTs. Thus short SRTs did not enable the attainment of readiness for task execution. An increased degree of headache symptoms and a decreased cardiovascular activity indicated that long SRTs were unsatisfactory and evoked boredom while waiting for the system's response. Work under medium SRTs yielded the best performance, a moderate level of heart rate and blood pressure and reduced the incidence of a negative self-assessment. In summary, it could be demonstrated that SRTs of a medium duration did enable the attainment of optimum readiness for task execution, while short SRTs did not. Long SRTs, which will generally limit the speed of work are not recommendable from a psychological and economic viewpoint. The results are discussed with respect to the concept of optimum duration of inter-task delays in performance for the particular task in question.