Development and evaluation of a model of human comfort and cognitive ability for moderate differences in thermal environment

Past research has established systematic effects of thermal stress on human comfort and cognitive performance. However, this research has primarily focused on extremes of temperature, ignoring moderate temperature ranges typically found in work environments and vehicles. Furthermore, models predicting the psychological impact of thermal environment have typically focused solely on perceived comfort, or when accounting for cognitive performance (e.g., Anno et al. 1996; Mueller et al. 2011) focused on in relatively extreme thermal conditions. As a consequence, there is limited empirical data, and no viable predictive models, for understanding the impact of moderate thermal stress on human comfort and performance. We report on an experimental study with 24 college-age participants that assessed cognitive performance (across a number of cognitive dimensions including manual dexterity, speed, dual-task performance, task switching, executive function, and attention), subjective measures of comfort and workload (including the CALM comfort scale, the affect grid, NASA-TLX, perceived effort, and other measures related to the thermal environment), and physiology (including heart rate, skin temperature, and breathing rate). Participants were tested during three 90-min sessions in a controlled thermal chamber in which the temperature was either cool (15 ºC/59 °F), room temperature (22.5 ºC/72.5 °F), or warm (30 ºC/86 ºF), during which they completed repeated rounds of comfort ratings, cognitive task performance, and rest. Results showed strong responses in physiological and comfort measures over time to differences in thermal environment. However, the thermal environment had differential effects on cognitive measures, with some producing little impairment, and others showing increases or decreases over time that were moderated by thermal environment. The results were examined within a latent variable model that suggests that comfort alone is not an adequate proxy for performance, even for moderate thermal stressors, and more complex predictive models are needed