208 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table III Mean Workload Scores in Practice and the Main Watch for Subjects in the Air, Muguet, and Peppermint Groups Groups Practice Main watch Mean Air 64.7 68.2 66.4 Muguet 69.4 68.0 68.7 Peppermint 63.6 62.3 63.0 Mean 65.9 66.2 Muguet or Peppermint groups. An analysis of variance of the data of Table III, however, failed to reveal any significant differences between groups or between phases (p 0.05). DISCUSSION The results of this experiment indicate that two fragrances, Peppermint and Muguet, when delivered periodically during the course of a 40-minute vigil, can have beneficial effects on subjects' performance in a vigilance task. Specifically, subjects exposed to either of the two fragrances showed greater overall sensitivity to signals than those receiving periodic whiffs of unscented air that result cannot be attributed to a change in subjects' willingness to emit detection responses, since the false alarm rates were equivalent in all groups. Moreover, the result cannot be due to differences among groups in the initial level of detectability of signals, since an analysis of variance revealed no group differences in hit rate during the practice task [F(2,33) = 2.16 p 0.05]. The data did not show an effect on the vigilance decrement itself: Subjects in all three groups performed less well as the vigil progressed than at the outset. Finally, there were no differences between men and women in performance efficiency, no interactions between gender and fragrance condition, and no effects involving time of day. So, we can conclude with some confidence that the effect of the two fragrances on ability to discriminate signals from non-signals has generality over sex and time of day. While we had reason to expect Peppermint (characterized as alerting) to be more effective than Muguet on performance measures, and Muguet (characterized as relaxing) to be the more effective on subjective reports of stress and workload, it is apparent that there was no difference between the two fragrances in their effect on performance efficiency and that neither had any dramatic impact on subjective reports. These latter results call into question the complicated scenario outlined earlier, that Peppermint facilitates vigilance performance by directly raising arousal level, whereas Muguet works through its ability to reduce the perceptually distracting effects of the symptoms of fatigue, tension, strain, headache, and so on, that typically arise in the vigilance situation. There are three simpler hypotheses that need to be tested: (a) given that both Peppermint and Muguet are assessed as very pleasant, perhaps any pleasant fragrance will suffice, and there is nothing physiologically/chemically special about these two fragrances (b) given that Peppermint and Muguet are both fragrances, perhaps any fragrance will suffice, pleasant, neutral or unpleasant, so long as it is judged either alerting or relaxing and finally, (c) it is possible that any perceptually salient fragrance will work by temporarily increasing subjects' alertness level via connections from olfac- tory centers to the midbrain reticular area (27), a brain region that plays an important

EFFECTS OF OLFACTORY STIMULATION 209 role in the regulation and maintenance of vigilance (28). These possibilities warrant further investigation. Finally, note that beyond providing the initial experimental demonstration that certain fragrances can bolster sustained attention, our results have meaning for an even broader issue, that of intersensory interaction. Studies of interactions among stimuli in different sense modalities have, for the most part, been confined to combinations drawn from the auditory, visual, and tactual modes (29). To our knowledge, the data described in this paper are the first to show that accessory olfactory stimulation can enhance the detection of visual stimuli. CONCLUSIONS The results of this study indicate that exposure to whiffs of air scented with the fragrance of Muguet or Peppermint can enhance the rate of signal detections in a vigilance task without a concomitant increase in errors of commission. These findings suggest that exposure to fragrance may serve as an effective form of ancillary stimulation in tasks demanding close attention for prolonged periods of time. ACKNOWLEDGMENTS This paper is based on an invited address given at the Annual Scientific Seminar of the Society of Cosmetic Chemists, San Francisco, CA, May 11, 1990, and a talk given at the Annual Meeting of the Psychonomic Society, New Orleans, LA, Nov. 17, 1990. We are grateful to Marina Munteanu, Craig Warren, and Steven Warrenberg of Inter- national Flavors and Fragrances, Inc., for suggesting that we undertake the research and for providing extensive technical assistance to Jonathan Gluckman, Sandy Matthews, Judith A. Thiemann, and Mary Anne Toledo, for invaluable help with instrumentation and data collection and to the Fragrance Research Fund for financial support. REFERENCES (1) D. R. Davies and R. Parasuraman, The Psychology of Vigilance (Academic Press, London, 1982), pp. 5-9. (2) J. S. Warm, "An Introduction to Vigilance," in Sustained Attention in Human Performance, J. S. Warm, Ed. (Wiley, Chichester, U.K., 1984), pp. 1-14. (3) K. Neuchterlein, R. Parasuraman, and W. Jiang, Visual sustained attention: Image degradation produces rapid sensitivity decrement over time, Science, 220, 327-329 (1983). (4) M. Frankenhaeuser, B. Nordheden, A. L. Myrsten, and B. Post, Psychophysiological reactions to understimulation and overstimulation, Acta Psychol., 35, 298-308 (1971). (5) U. Lundberg and M. Frankenhaeuser, Pituitary-Adrenal and Sympathetic-Adrenal Correlates of Distress and Effort, Report No. 548 (University of Stockholm Department of Psychology, Stockholm, 1979). (6) C. A. Hovanitz, K. Chin, and J. S. Warm, Complexities in life stress•lysfunction relationships: A case in point--Tension headache, J. Behav. Med., 12, 55-75 (1989). (7) R. I. Thackray, J. P. Bailey, and R. M. Touchstone, "Physiological, Subjective and Performance Correlates of Reported Boredom and Monotony While Performing a Simulated Radar Control Task," in Vigilance: Theory, Operational Performance and Physiological Correlates, R. R. Mackie Ed. (Plenum, New York, 1977), pp. 203-215. (8) J. D. Deaton and R. Parasuraman, "Effects of Task Demands and Age on Vigilance and Subjective