The Restriction of Peripheral Vision during Exposure to Hot and Humid Conditions

Abstract

Eighteen, heat-acclimatized subjects were exposed to temperatures of 70/60° F. and 105/95° F. (air velocity 120 ft./min.) in three experiments requiring them to respond to a peripheral task concurrently with a continuous central pursuitmeter task. The peripheral signals were presented randomly in order and time at six positions, 20°, 50°, and 80° left and right to the point of fixation. The experimental findings suggest that when, while being subjected to high thermal conditions, operators are engaged in a central task consistently demanding their attention, there is a tendency for the field of awareness to be funnelled towards the centre. Signals presented at greater eccentric angles have a higher probability of being missed in the hotter condition. The longer the previous exposure to heat, the greater is the tendency to miss signals—but the effect does not always appear to be progressive during the actual performance. Operationally, the funnelling is defined by the proportional increase in the number of signals missed as the eccentric angle of the stimulus increases relative to the point of fixation. The phenomena does not occur when the perceptual load on the central task is reduced. Central attentional processes rather than mechanisms peripheral to the CNS are therefore implicated.