Elisabeth Schmidt investigates the effect of thermal stimulation during passive driver fatigue in a series of driving simulator experiments. Thermal stimulation of the upper body resulted in significantly decreased subjective fatigue ratings as well as an increase in pupil diameter and skin conductance. The effects of different stimulus temperatures, durations, lower leg cooling and repetitive cooling were also examined. The studies show that thermal stimulation of the upper body causes physiological and subjective effects, which can be associated with a short-term sympathetic activation, whereas lower leg cooling does not cause physiological activation.