Sustained attention under thermal stress.

This article reviews the effects of the thermal environment on vigilance. A reinterpretation of early and contemporary studies contradicts the existing notion that vigilance is facilitated in ambient temperatures that exceed a comfortable level. Rather, performance is degraded as thermal homeostasis of the observer is disturbed. Significant breakdown in capability becomes manifest with measurable perturbation to deep body temperature. This assertion requires that conditions induce a dynamic change, as performance is unaffected with no variation in deep body temperature and is facilitated when the observer is established in a static hyperthermic state. An attentional account of this phenomenon is offered, which contrasts with previous arousal explanations.