A review of the effects of high ambient temperature on mental performance. AMRL-TR-65-102.

Abstract : Fifteen experiments done in various laboratories have assessed the effects of high thermal stress on mental performance. These experiments represent different combinations of exposure time and effective temperature. These studies were reviewed, and the upper thermal limit for unimpaired mental performance was found to vary systematically with exposure duration. Specifically, the lowest test temperatures yielding statistically-reliable decrements in mental performance decline exponentially as exposure durations are increased up to 4 hours. When this temperature-duration curve for mental performance is compared with physiological tolerance curves, it is found to lie well below them at every point in time.