Male Pheromones and Sexual Attraction
ABSTRACT
Previous research has revealed that natural and synthetic pheromones can enhance ratings of opposite sex attractiveness.
The present study investigated the effects of exposure to male axillary secretions on female ratings of the sexual attractiveness of male stimuli.
Thirty-two female undergraduates, half of whom were contraceptive pill users, rated male vignette characters and photographs of male faces on aspects of attractiveness. On two separate study days, corresponding to different phases of their menstrual cycle, stimuli were presented while exposed to male axillary pheromones and under a control condition (no pheromone).
The order of testing was balanced with respect to pheromone/control condition and menstrual cycle phase.
Pheromone exposure resulted in significantly higher attractiveness ratings of vignette characters and faces.
Use of the contraceptive pill or menstrual cycle phase had equivocal effects on some vignette items and neither had any influence on female ratings of male facial attractiveness.
The results of this study suggest that exposure to natural male axillary pheromones can significantly enhance female perceptions of various aspects of male attractiveness.
Introduction
Pheromones are biologically-active substances released by an individual, and received by another individual of the same species, in whom they activate specific physiological or behavioural responses [1].
Pheromones are therefore referred to as ecto-hormones: chemical messengers that are transported outside the body that have the potential to evoke certain responses in a conspecific.
The physiological and behavioural effects of pheromones have been well documented in many invertebrate and vertebrate species (for reviews see [2, 3]) though their putative effects on human behaviour and physiology remain equivocal. Scepticism concerning the existence of human pheromones was due in no small part to the lack of clear evidence for the existence of a fully functioning vomeronasal organ (VNO). In many animal species this system has been shown to detect pheromones and transmit this information to limbic structures via the vomeronasal-terminalis nerves (for review see [4]).
However, it has since been reported that humans do possess a functional VNO that responds to pheromones – even in picogram amounts – in a sex-specific manner, and produces specific physiological changes [5, 6, 7].
Recently, the identification of a pheromone receptor gene expressed in human olfactory mucosa has further strengthened the case for a functioning VNO [8].
The main producers of human pheromones are the apocrine glands of the skin located in the axillae of the armpits and pubic region. The high concentration of apocrine glands found in the armpits, led to the term ‘axillary organ', which is considered an independent ‘organ' of human odour production.
Apocrine glands develop in the embryo, but become functional only with the onset of puberty. At sexual maturation, they produce steroidal secretions derived from 16-androstenes (androstenone and androstenol) via testosterone, and as such, the concentrations of several 16-androstenes is significantly higher in males [9].
The action of aerobic bacteria further serves to metabolise the more odorous androstenone and androstenol [10]. The 16-androstenes have been confirmed as male sexual pheromones in pigs [11] and several authors have speculated that such substances may act as human male pheromones subserving sociosexual behaviours [12, 13].
In support, several studies have shown that when exposed to androstenol (often described as a pleasant ‘sandlewood' smell when detected), female ratings of male attractiveness are enhanced higher [14, 15, 16]. Filsinger, Braun, and Monte [17] showed that men under the influence of androstenone rated photos of males positively, if they liked the scent of androstenone. However, other authors have reported that exposure to androstenone (often described as ‘urine-like' or ‘musky') induces negative perceptions of males [18].
Grammer [12] has argued that there are two different olfactory signals – androstenol, which induces female attraction to males, and androstenone, which induces negative responses in females. Further, though pheromonal communication typically occurs without conscious awareness, pheromones, when produced in high concentrations, may still have both conscious and aversive effects on others.
This is further complicated by the fact that female olfactory sensitivity is moderated by the menstrual cycle, with smell sensitivity peaking at ovulation [19, 20]. Benton [20] reported that androstenol application influenced ratings of subjective mood at ovulation, and Grammer [12] found that females rated androstenone differently at various phases of their menstrual cycle. Thus, it has been suggested that human body odour influences female mate choice in terms of evolutionary principles.
Women seem to prefer the odours of immunocompatible men [21] and, during their fertile period, judge the body odours of men with symmetrical bodies (indicative of genetic quality) as more pleasant [22] which is indicative of genetic quality.
A further complication when evaluating the results from such studies is that the use of oral contraception may affect smell sensitivity and gonadal hormone levels [23] thereby possibly disrupting pheromone detection. Use of the contraceptive pill does indeed appear to influence female perception of androstenone [12].
The present study aimed to determine whether naturally occurring pheromones might act as sexual attractants in humans. Young female participants, half-using oral contraception, and half not, were unknowingly exposed to pure male axillary secretions (unaffected by coryeform bacteria and therefore not consciously odorous) during two phases of their menstrual cycle. On four separate occasions (pheromone present and pheromone absent at two different times of the menstrual cycle) females rated male attractiveness using vignette characters and photographs.
NEUROENDOCRINOLOGY LETTERS
including Psychoneuroimmunology, Neuropsychopharmacology,
Reproductive Medicine, Chronobiology and Human Ethology
ISSN 0172–780X
NEL Vol.23 No.4, August 2002
2002; 23:291–297
pii: NEL230402R03
REVIEW ARTICLE
PMID: 12195229
Free full text online pdf [439 kb]
Frances Thorne 1, Nick Neave 1, Andrew Scholey 1, Mark Moss 1 & Bernhard Fink 2 1. Human Cognitive Neuroscience Unit, Division of Psychology, Northumbria University, Newcastle upon Tyne, UNITED KINGDOM.
2. Ludwig-Boltzmann-Institute for Urban Ethology, University of Vienna, Austria.
Submitted: June 8, 2002
Accepted: June 18, 2002
[J. Smith PhD]