Environra~nt International, Vol. 17, pp. 229-234, 1991 0160-4120/91 $3.00 + .00 Printed in the U.S.A. AUrights reserved. Copyright © 1991 Pergamon Press plc THE INTERACTION OF NOISE AND MILD HEAT ON COGNITIVE PERFORMANCE AND SERIAL REACTION TIME Staffan Hygge The National Swedish Institute for Building Research, S-801 29 G~vle, Sweden E1 9004-046M (Received2 April 2990; accepted10 October 1990) In a 2x2 factorial design two noise levels (38 dBA and 53 dBA) were crossed with two temperature levels (19°C and 27°C). A total of 64 subjects completed a 2-h, 20-rain session, working with mental arithmetic, a recognition task, hidden geometrical figures, proofreading, verbal fluency, and the five-choice serial reaction task. In a pre-test session, exactly 24 h before the experiment proper, subjects worked with parallel versions of the very same tests in 38 dBA and 20°C. Multivariate analyses of variance were performed on the difference in performance between the two sessions. Results indicated an antagonistic interaction between heat and noise on the hidden figures test. For the recognition task, noise biased the response criterion towards being stricter. On the five-choice task, the higher temperature increased the rate of responding without increas- ing errors. Results are discussed in terms of arousal and overload theories. INTRODUCTION Two stressors affecting the same psychological mechanism should yield an interaction, whereas two stressors affecting different mechanisms should not. Tapping the same underlying mechanism should show up as an antagonistic (canceling effects) or synergis- tic (more than additive) interaction. Effects routed along different paths would be indicated by additive or parallel effects. Thus, studies of the interaction between two different kinds of stimulation may yield valuable theoretical insights into the mediating psy- chological mechanisms. Explanations of an interaction between heat and noise on performance have often employed an arousal theory including the inverted U-hypothesis and Easterbrook's (1959) cue-utilization hypothe- sis (Hockey and Hamilton 1983). The inverted U- hypothesis states an inverted U-shape relation- ship between arousal and task performance. Persons who are either above or below some optimal arousal point will suffer performance decrements. Further- more, increased task difficulty moves the optimal a- rousal point downwards on the arousal continuum. Easterbrook's (1959) cue-utilization hypothesis pro- posed an explanation for why high arousal levels impede performance. The explanation is that high levels of arousal narrow the focus of attention so that only the cues that are perceived to be central to task performance are attended to. If these cues indeed are the central ones, performance will improve. If not, performance will deteriorate. From this theoretical perspective, and if noise is assumed to increase arousal and mild heat to decrease it, an antagonistic interaction between the two would 229