Perceptual Narrowing in Novice Divers

It was hypothesized that in diving, danger-induced stress may contribute to performance decrement by narrowing perceptual scope. A study was conducted to examine the effect of task load and type of underwater exposure on response time to a signal light in the visual periphery. Novice divers monitored a peripheral light alone, or while simultaneously performing a central addition or dial-watching task. Each subject was tested on the surface, in a diving tank, and in the open ocean. It was found that the central tasks did not interfere with peripheral vigilance on the surface. During diving, a distinct subgroup of the dual-task subjects exhibited markedly increased response times to the peripheral light while maintaining near constant performance on the central tasks. Their behavior appeared more closely related to diving risk than to other environmental factors. The remaining dual-task subjects, and the light alone group, were almost uneffected by underwater exposure. The hypothesis was considered partially validated.