j. Soc. Cosmet. Chem., 42, 199-210 (May/June 1991) Effects of olfactory stimulation on performance and stress in a visual sustained attention task JOEL S. WARM, WILLIAM N. DEMBER, and RAJA PARASURAMAN, Department of Psychology, University of Cincinnati, Cincinnati, OH 45221 (J.S.W., W.N.D.), and Department of Psychology, The Catholic University of America, Washington, DC 20064 (R.P. ). Received December 5, 1990. Presented at the Annual Meeting of the Society of Cosmetic Chemists, San Francisco, May 1990. Synopsis Subjects performed a visual sustained attention (vigilance) task for 40 minutes during which they received periodic 30-second whiffs of pure air or a hedonically positive fragrance, Muguet or Peppermint, through a modified oxygen mask. The former fragrance had been independently judged as relaxing, the latter as alerting. Subjects receiving either fragrance detected significantly more signals during the vigil than unscented air controls. Subjective reports of mood and workload indicated that the subjects experienced the vigilance task as stressful and demanding. However, the fragrances had no impact on the latter measures. These results provide the initial experimental evidence to indicate that fragrances can enhance signal detectability in a task demanding sustained attention, though the exact characteristics of effective fragrances have yet to be determined. INTRODUCTION Vigilance, or sustained attention, tasks require observers to remain alert and to detect infrequent and unpredictable stimulus events over prolonged periods of time (1-2). Although subjects engaged in such tasks are required only to dedicate themselves to looking or listening for the specified events that constitute signals for detection, their performance on these tasks is remarkably fragile, and the tasks tend to induce consid- erable stress. The brittle character of vigilant behavior is revealed through the decrement function, a decline in the frequency and/or speed of signal detections over time. This decline is often complete from 20 to 35 minutes after the initiation of the vigil (1-2) in some cases, it can even be observed as early as the first five minutes of watch (3). Along with the decrement function, vigilance performance is accompanied by increased catecholamine and cortisol output, indicating physiological stress (4-5), and by subjective reports indicating that monitors feel less energetic, more strained, bored, irritated, drowsy, and 199

200 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS headachy at the end of a vigil than at the beginning (6-7). Moreover, measures of subjective workload show that what may appear to be a simple assignment is in fact quite demanding (8-9). For obvious practical reasons, it would prove very useful to develop techniques for improving the overall level of vigilance performance, for moderating the vigilance decrement, and for alleviating the feelings of stress attendant on engaging in vigilance tasks. Such tasks can be found in many work settings, including those confronting radar and sonar operators, quality control inspectors, system monitors in power plants, med- ical personnel in intensive care units, long distance drivers, and so on. Failure to detect and respond to critical signals in these settings can sometimes have disastrous conse- quences (2). Efforts to moderate the vigilance decrement and combat the feelings of stress induced by vigilance tasks have utilized exercise (10), added stimulation such as music in a visual vigilance task or visual stimulation in an auditory task (11-12), and stimulant drugs (13-14) to keep monitors aroused. While somewhat successful, these techniques have limitations. Exercise at the workstation is not always possible, added stimulation can be distracting and impair working memory (15), and drugs can produce unwanted side effects and addiction (16). To our knowledge, no one, prior to the present study, has appealed to the olfactory sense as a source of stimulation for the maintenance of sustained attention. Olfactory stimuli can be quite salient and can play important roles in emotion and in recall and recog- nition (17-18). There is also evidence that some fragrances can enhance alertness and that some can reduce stress, at least on a short-term basis. While this evidence is in part anecdotal (19), much of it comes from empirical research using both psychophysiological and self-report techniques (20-21). If the purported alerting and stress-reducing prop- erties of fragrances can operate over extended periods of time, fragrance administration might serve as a benign vehicle for enhancing the quality of sustained attention and/or reducing the stressful feelings that accompany vigilance performance. Our hypothesis was that fragrances assessed as alerting might beneficially affect vigilance performance and that fragrances assessed as relaxing might reduce the tension and feelings of stress consequent on performing a vigilance task. Moreover, we were prepared to speculate that alerting fragrances might also reduce the stress of vigilance by creating a closer match between task demands and subjects' ability to perform those tasks that is, part of the stress may arise from subjects' need, but inability, to remain sufficiently alert to do well on the vigilance task. Fragrances that help them stay alert might therefore also help them feel better. Similarly, relaxing fragrances might affect perfor- mance efficiency as well as feelings, since subjects who are tense and uncomfortable may find it hard to concentrate on the task. In short, it seemed reasonable to expect that both alerting and relaxing fragrances might have both performance- and mood-enhancing effects, albeit for somewhat different reasons. But our main concern, at the outset, was whether we could find any effects of fragrance at all in comparison with an appropriate control condition. For our initial investigation, we decided to use two hedonically positive fragrances, one assessed as alerting and the other as relaxing. Toward that end, the initial phase of the research involved an evaluation of the hedonic and mood-inducing qualities of seven fragrances supplied by International Flavors and Fragrances, Inc.: Benzoin, Cashmeran,