J. Soc. Cosmet. Chem. 27 319-327 (1976) ¸ 1976 Society ooe Cosmetic Chemists ooeGreat Britain Sex differences in odour perception E. P. KOSTER and H. S. KOELEGA* Presented at the Symposium on 'A Sensory Approach to Cosmetic Science', organized by the Society of Cosmetic Chemists of Great Britain at Manchester on 8 April 1975. Synopsis--Men and women seem to differ in their SENSITIVITY and VARIABILITY to, and appreciation of, odorous substances. The differences in sensitivity seem to be particularly marked for substances which have a biological significance because they act in the animal world as SEXUAL ATTRACTANTS. The differences in sensitivity to these substances are probably due to changes in sensitivity which occur in the female population around puberty. Older findings about the variations of the olfactory sensitivity of women during the course of the MENSTRUAL CYCLE also sug- gested a link between OLFACTORY SENSITIVITY and HORMONE action, but it is not yet completely clear in which way this interaction takes place. INTRODUCTION Odours and the sense of smell play an important part in the sexual attraction and the sexual behaviour of many animal species. Whether olfactory communication is also an important factor in the sexual behaviour of man is still a completely open question. In recent years, a large amount of money and effort has been put into the search for a possible human sex attractant or 'pheromone', but little has come out of this so far. The research on sex differences in odour perception reported here has different and much older origins and is only indirectly relevant to the question of the existence of a human pheromone. The question asked here is simply whether men and women differ in their perception of odours and if so, what possible mechan- isms might be responsible for the differences in odour perception found. Whether or not such differences may also have a functional meaning in human sexual behaviour cannot be decided on the basis of these experiments alone. * Psychology Department, University of Utrecht, Utrecht, The Netherlands. 319

320 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Three kinds of differences in odour perception between men and women will be discussed: (a) differences in sensitiv/ty to low concentrations of odours (b) differences in variability of the sensitivity to odours (c) differences in the qualitative appreciation of odours. DIFFERENCES IN OLFACTORY SENSITIVITY In 1899 Toulouse and Vaschide (1) reported on the already conflicting results of research workers concerning differences in olfactory sensitivity between men and women. Since then there have been a number of authors who found no such differences but others, often using more refined techniques and more carefully selected odorous substances, reported that women were often more sensitive to odours than men. However, even today there is conflicting evidence. Le Magnen (2) used among other substances a musk-like odour called 'exaltolide' (cyclo-pentadecanolide) and found that for this substance the sex difference was rather large. According to him adult women are very sensitive to cyclo-pentadecanolide whereas young children and adult men do not perceive the odour at all, or find it very weak. Le Magnen (2) claimed that these differences were specific for the sensitivity to cyclo-pentadecanolide and urinoid odours like pyridine. On the basis of these findings he formulated the hypothesis that the sensitivity of these 'biologically significant' odours is determined by sex hormones. Oestrogens would improve sensitivity to them whereas androgens would diminish the sensitivity to the biologically significant odours but in contrast would improve the sensitivity to other odours like safrol, phenol etc. Le Magnen (3) reported that in rats, androgens seem to develop the sensitivity to the musky odour to which adult male rats are the most sensitive. Pietras and Moulton (4) also found that male rats are, on the average, more sensitive than female rats, not only for exaltolide, but also for 'neutral' odours. Le Magnen's (2) 'specific' hypothesis stands in contrast to a more 'general' hypothesis formulated by Broverman et al. (5). Broverman (5) supposed that sex differences in cognitive tasks, conditioning and in sensory thresholds are reflections of the balance be- tween the activating influence of central adrenergic processes and the inhibitory influence of central cholinergic processes, which in turn, are influenced by the gonadal steroid sex hormones, androgens and oestrogens. Since the oestrogens are more potent activating agents than the androgens, females are more activated, or less inhibited than males. This would manifest itself also in a higher feminine sensory sensitivity. Koelega (6) Koelega and K6ster (7) tested these hypotheses. The olfactory thresholds of adult men and women and of children before and during puberty were determined. A number of different substances both from a 'biologically