Biol. Lett. doi:10.1098/rsbl.2005.0332 Published online
Womens preference for dominant male odour: effects of menstrual cycle and relationship status
Jan Havlicek(1),*, S. Craig Roberts (2) and Jaroslav Flegr (3) (1) Department of Anthropology, Faculty of Humanities, Charles University, Husnikova 2075, 155 00 Prague, Czech Republic
(2)Evolutionary Psychology and Behavioural Ecology Research Group, School of Biological Sciences, University of Liverpool, Liverpool L69 3BX, UK
(3)Department of Parasitology, Faculty of Science, Charles University, Vinicna 7, 127 44 Prague, Czech Republic *Author for correspondence ( jan.havlicek@fhs.cuni.cz)
Body odour may provide significant cues about a potential sexual partners genetic quality, reproductive status and health. In animals, a key trait in a females choice of sexual partner is male dominance but, to date, this has not been examined in humans. Here, we show that women in the fertile phase of their cycle prefer body odour of males who score high on a questionnaire-based dominance scale (international personality items pool). In accordance with the theory of mixed mating strategies, this preference varies with relationship status, being much stronger in fertile women in stable relationships than in fertile single women.
Keywords: attractiveness; scent; smell; good genes; mate choice; sexual selection
1. INTRODUCTION In many systems, dominance-associated traits have been suggested as honest signals of male genetic quality. Several studies on rodent species have reported preferences for the odour of dominant males (e.g. Mossman & Drickamer 1996; Kruczek 1997; Gosling & Roberts 2001). Odour cues may also play a substantial role in human mate choice. For instance, women prefer the smell of men with low fluctuating asymmetry (Thornhill & Gangestad 1999), which is considered to be a marker of genetic and developmental stability and is an important factor influencing visual attractiveness (Gangestad & Simpson 2000). In addition, humans prefer the scent of opposite-sex individuals with major histocompatibility complex (MHC) genes that are dissimilar (Wedekind et al. 1995; Wedekind & Fu¨ ri 1997) or intermediately dissimilar ( Jacob et al. 2002) to their own (see also Thornhill et al. 2003). Such preferences might result in more viable offspring (Penn 2002). It has also been observed that preference for mens scent depends on the menstrual cycle phase of women. In controlled experiments, only the women near peak fertility within their cycle preferred scent of men with low fluctuating asymmetry
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(Gangestad &Thornhill 1998; Rikowski & Grammer 1999; Thornhill & Gangestad 1999; Thornhill et al. 2003). Similarly, research on facial attractiveness indicates that female preference for visual masculinity (a trait putatively correlated with dominance) varies across the cycle (Penton-Voak et al. 1999) and with partnership status (Little et al. 2002). In this study, we investigated whether womens preference for odour of dominant males also varies cyclically and between single women and those in stable relationships.
2. METHODS (a) Odour stimuli Forty-eight male students aged between 19 and 27 were asked to complete an 11-item questionnaire on dominance from the international personality items pool (http://ipip.ori.org/ipip/; Goldberg 1999) and to wear cotton pads in their armpits for 24 h. Pads (Premium cosmetic pads, Boots, www.boots.co.uk) were 100% cotton, elliptical in shape, approximately 9!7 cm at their longest axis and held in place using MicroporeTM surgical tape (Boots). The questionnaire was used in its original form and corresponds to the scale Narcissism in the widely used California psychological inventory (CPI). Subjects were instructed to avoid spicy and smelly food, alcohol, smoking or using any scented cosmetics on both the evening before and during the day when they were wearing the pads. (b) Subjects and experimental procedure Freshly collected pads were presented to 30 female students (mean age 20.6 years) in their follicular phase (days 9 to 15) and to 35 female students (mean age 20.2 years) in other phases of the cycle. The range of days included as falling into the follicular phase (i.e. fertile period) was based on results showing that probability of conception is highest within this fertile window (Wilcox et al. 2000). None of the women were using hormonal contraception. Each of them rated the odour of 10 pads for their intensity, sexiness and masculinity using a 7-point scale. The ratings from each woman were converted to z-scores to compute the correlation between male odour and male dominance as measured by the questionnaire. The obtained correlation coefficients showed a normal distribution and, therefore, were compared with random expectation (rZ0) using one-sample t-tests. Although our design is between-subjects in nature, this should tend to make our results conservative compared with a within-subjects design.
3. RESULTS We found a positive correlation between male psychological dominance assessed by the questionnaire and odour sexiness when rated by women in their fertile phase (t29Z3.1, pZ0.004, mean rZ0.20) but not in other phases of their cycle. Subsequently, we tested separately the women who reported to be single and those who were in a heterosexual romantic relationship. A strong association between male odour sexiness and psychological dominance was only found for non-single women in the fertile phase of their menstrual cycle (t12Z4.4, pZ0.0008, rZ0.29; figure 1). There was no significant correlation between male psychological dominance and perceived masculinity of their body odour when rated by single women, regardless of phase of their cycle. In contrast, we found a negative correlation between male dominance and intensity of body odour for both female subsamples (fertile phase of the cycle, t29Z2.3, pZ0.03, rZK0.13; rest of cycle, t34Z3.0, pZ0.005, rZK0.18; figure 2). As this effect was observed irrespective of menstrual cycle phase, the shifts in attractiveness of dominant males cannot be explained by variation in odour sensitivity across the cycle (Doty et al. 1981).
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by women in the fertile phase but not other phases of the cycle (Gangestad & Thornhill 1998; Rikowski & Grammer 1999; Thornhill & Gangestad 1999; Thornhill et al. 2003). Several studies also report that women in the fertile phase of their cycle prefer relatively more masculine faces (Penton-Voak et al. 1999; Penton-Voak & Perrett 2000; Johnston et al. 2001). The relative preference for more masculine faces was found also when rated by single women or in a short-term partnership context (Little et al. 2002). All of the above-mentioned studies are congruent with our findings and support the hypothesis about female mixed mating strategies dependent on their cyclical and partnership states. The proximate mechanism responsible for the correlation between psychological dominance and odour sexiness is unknown. Nevertheless, previous studies have shown that emotional state (e.g. fear or happiness) may influence perception of body odour quality (Chen & Haviland-Jones 2000; Ackerl et al. 2002). The higher self-confidence of dominant males may also have an impact on the perceived sexiness of their body odour. We thank all volunteers for their participation in the study, two anonymous referees for their comments on the manuscript and Jindra Jileckova for language corrections. This study was supported in part by the NATO Science Fellowship and the Owen F. Aldis Fund (J.H.) and grant no. 0021620828 awarded to J.F. by the Czech Ministry of Education.
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