ON THE MEASUREMENT OF DETERIORATION IN PERFORMANCE CAUSED BY DISTRACTION STRESS

Abstract

This study is a first step to a closer quantitative description of the step-by-step deterioration in performance of complex behaviour patterns that can be brought about by increasingly occupying the subject mentally with another task to which he has to give preference. This method may be regarded as providing ’ distraction stress ’

The task to which preference had to be given (Primary Task) consisted of pressing a pedal at the left or right in response respectively to a low and a high tone presented in random order through earphones. The Secondary Task consisted of placing rods into holes. Different conditions of Secondary Task were chosen in order to compare measures of the impairment caused by the Primary Task to movement, positioning and the making of choices in the Secondary. When the Secondary Task required only movement or movement and positioning, the effect of the Primary Task was mainly expressed in slower performance. When the Secondary Task also required choices at be made errors also tended to occur.

Observations of the subjects’ performances suggested that skill at doing two tasks at the same time may be thought of as the building up of an ability to send messages in alternating patterns through a single central output channel by using moments during concurrent movements of hand or foot when these are not being monitored. This appeared to be achieved when the Secondary Task did not require choices to be made. When the Secondary Task did require the making of choices it did not seem possible to achieve such a stable interdigitated pattern of decisions.

∗ Attached to Coronel Laboratory of Occupational Hygiene, University of Amsterdam.

Notes

∗ Attached to Coronel Laboratory of Occupational Hygiene, University of Amsterdam.