The effects of different vertical air temperatures on mental performance

Mental performance (one-digit-addition test) under conditions of different vertical air temperatures (upper body vs. lower body) was studied in relation to psychological and physiological responses. Six healthy male subjects wearing light clothing were exposed to different vertical air temperatures for 105 min. The lower part of the body was exposed to an air temperature of 30 degrees C in all cases; the upper part of the body was exposed to temperatures of 15 degrees C, 20 degrees C, 30 degrees C and 35 degrees C. The performance in the one-digit-addition test decreased with increased upper air temperature, and upper air temperatures higher or lower than 25 degrees C resulted in increased discomfort. There was little difference between performance at the onset (5 min after exposure) and conclusion (90 min after exposure) at 15 degrees C and 20 degrees C upper air temperatures (UAT). The performance at 90 min, however, declined in comparison with the original value at 25 degrees C, 30 degrees C and 35 degrees C UAT. Mildly uncomfortable ambient conditions where upper air temperatures were cool and lower air temperatures were warm improved performance; however, at 35 degrees C, UAT performances worsened as the subjects felt uncomfortably hot.