Body Temperature and Information Processing Capability

Typically, human performance is projected to fluctuate in a circadian manner, usually in association with body temperature rhythm. Such sinusoidal relationships are isomorphic in that they are, under most normal circumstances, phase-locked in environmental time. As body temperature rises so performance is improved. However, increase in temperature above the zenith does not result in increased capability. Rather, such elevation has the dual and opposing action of speeding performance while elevating error rate to produce an overall diminution of efficiency (e.g., Allan and Gibson, 1979; Nunneley, Reader, and Maldonado, 1982). It has been suggested that deep body temperature controls the speed of performance, while skin temperature mediates error through the control of comfort associated with peripheral variation. To overcome distress connected with peripheral increase, yet to utilize the superior speed elicited by alteration of central temperature change, the use of selective head heating has been explored. The present paper synthesizes data from selective heating studies and indicates the potential gains which may be realized in complex machine operation. Results from this paradigm have suggested facilitation in stimulus assimilation, decision making capability and response selection and execution (e.g., Hancock, 1983; Hancock and Dirkin, 1982; Holt and Brainard, 1976). This facilitation is not linear in temperature change. To a 1°C increase there appears a change in decision criterion such that individuals become more conservative in response. Above this threshold value, veridical gains in performance are manifest with a reduction in both task latency and error rate. Simple physiological accounts of such behavior are largely inadequate as the precise physiological effect has yet to be thoroughly documented. An initial outgrowth of this work is the potential usage of fluctuation in head temperature as a dynamic physiological reflection of imposed mental workload (e.g., Hancock, Meshkati, and Robertson, 1984). These performance facilitations under relatively slow temperature changes are contrasted with decrement observed under rapid temperature fluctuation. A potential relationship with the notion of attentional resource capacity is explored.