The effects of increased ambient temperature on dual task performance

Abstract

This dissertation reports on the effects of two levels of increased ambient temperature on the performance of a tracking task and a variety of secondary mental tasks. Eighteen males, ages 18 - 29, were exposed to wet bulb globe temperatures of 18.5, 28.6 and 32.9 degrees centigrade in three sessions, each of two hours duration. The first hour was used for training and practice while the subjects' skin and core temperatures stabilized. During the second hour, measurements were taken of subjects' performance on the tracking task and on six secondary tasks, performed singly and in combination with the primary task. The tasks selected were the Stroop test, a mental arithmetic test, a visual search task, a decoding task and a performance evaluation test that involved signal identification and the retention of three numerical registers in short term memory. A vigilance task was also presented, with three signals occurring at random intervals during that hour. Significant performance decrements due to increased ambient temperature were observed for the vigilance task, the reaction time test and the Stroop test. These constitute the least complex mental tasks. It must be concluded that for the intelligent, highly motivated subjects used in this experiment, simple tasks involving a minimum of mental effort are more sensitive to Effective Temperatures up to 32.2 degrees Centigrade (90 degrees Fahrenheit) for exposure times between one and two hours. For the sedentary tasks at the ambient conditions used in this experiment, the subjects were able to thermoregulate quite successfully. The average increase in the body core temperature for the hottest condition was only 0.4 degrees Centigrade. It appears, from these results, that complex mental tasks remain unaffected by ambient conditions that produce only minor changes in the physiological state. There was, however, a trend towards performance decrements for the most difficult tasks at the highest temperatures...