Contextualising courtship: Exploring male body odour effects on vocal modulation

Voice characteristics are important to communicate socially relevant information. Recent research has shown that individuals alter their voices depending on the context of social interactions and perceived characteristics of the audience, and this affects how they are perceived. Numerous studies have also shown that the presence of bodily odours can elicit psychological changes in people. Here, we tested whether the presence of male axillary odour would influence vocal modulations in courtship contexts. We analysed differences in vocal parameters and attractiveness ratings across 950 recordings from 80 participants as they responded to opposite-sex target stimuli. Using these, we tested whether men’s and women’s vocal parameters and perceived attractiveness differed in the presence or absence of the odour. We expected women to speak with increased voice F0, and men to lower their pitch, when exposed to male body odour, especially if it were of high quality. However, neither the presence of male odour, its quality, nor the addition of androstadienone produced any consistent changes in vocal parameters. Nevertheless, rated stimulus attractiveness was predicted by F0 and especially F0 variability, suggesting that this is a key parameter in signalling attraction during human courtship, and supporting the idea that vocal modulations are context-sensitive.

Losing stinks! The effect of competition outcome on body odour quality

Dominance hierarchy is often established via repeated agonistic encounters where consistent winners are considered dominant. Human body odour contains cues to psychological dominance and competition, but it is not known whether competition outcome (a marker of a change in dominance hierarchy) affects the hedonic quality of human axillary odour. Therefore, we investigated the effect of winning and losing on odour quality. We collected odour samples from Mixed Martial Arts fighters approximately 1 h before and immediately after a match. Raters then assessed samples for pleasantness, attractiveness, masculinity and intensity. We also obtained data on donors' affective state and cortisol and testosterone levels, since these are known to be associated with competition and body odour quality. Perceived body odour pleasantness, attractiveness and intensity significantly decreased while masculinity increased after a match irrespective of the outcome. Nonetheless, losing a match affected the pleasantness of body odour more profoundly, though bordering formal level of significance. Moreover, a path analysis revealed that match loss led to a decrease in odour attractiveness, which was mediated by participants’ negative affective states. Our study suggests that physical competition and to some extent also its outcome affect the perceived quality of human body odour in specific real-life settings, thus providing cues to dominance-related characteristics. This article is part of the Theo Murphy meeting issue ‘Olfactory communication in humans’.

Characterizing human odorant signals: insights from insect semiochemistry and in silico modelling

Interactions relating to human chemical signalling, although widely acknowledged, are relatively poorly characterized chemically, except for human axillary odour. However, the extensive chemical ecology of insects, involving countless pheromone and other semiochemical identifications, may offer insights into overcoming problems of characterizing human-derived semiochemicals more widely. Current techniques for acquiring insect semiochemicals are discussed, particularly in relation to the need for samples to relate, as closely as possible, to the ecological situation in which they are naturally deployed. Analysis is facilitated by chromatography coupled to electrophysiological preparations from the olfactory organs of insects in vivo . This is not feasible with human olfaction, but there are now potential approaches using molecular genetically reconstructed olfactory preparations already in use with insect systems. There are specific insights of value for characterizing human semiochemicals from advanced studies on semiochemicals of haematophagous insects, which include those involving human hosts, in addition to wider studies on farm and companion animals. The characterization of the precise molecular properties recognized in olfaction could lead to new advances in analogue design and a range of novel semiochemicals for human benefit. There are insights from successful synthetic biology studies on insect semiochemicals using novel biosynthetic precursors. Already, wider opportunities in olfaction emerging from in silico studies, involving a range of theoretical and computational approaches to molecular design and understanding olfactory systems at the molecular level, are showing promise for studying human semiochemistry. This article is part of the Theo Murphy meeting issue ‘ Olfactory communication in humans ’.

Axillary odour studies on alkali-treated knitted polyester fabric

Purpose Odour formation in textile material is mainly based on the fibre content and also the constituent fibres’ chemical and physical structures. Polyester fibre materials are very profound to form odour after being worn due to their highly oleophilic nature. The purpose of this paper is to analyse the odour formation characteristics of polyester fabric after surface modification through alkali treatment. Design/methodology/approach Five male participants were allowed to use the alkali-treated and untreated polyester fabrics, which were fixed in the axilla region of their vest. Subjective and objective odour analyses were performed for the worn samples. The odour was evaluated in terms of intensity rating, bacterial population (CFU/ml) and bacterial isolation. Findings The results showed that alkali treatment was effective in odour reduction in polyester fabric (p<0.005). The bacterial population density was also reduced significantly (p<0.005) in the alkali-treated polyester fabric compared to the untreated polyester fabric after the wear trial. The alkali treatment affected the surface structure of the polyester fabric and thus changed it from hydrophilic to hydrophobic. This was confirmed by the moisture management test results. Originality/value The odour formation in the polyester fabric can be controlled by simple surface modification process like alkali treatment, and thus the value of the product can be increased in the apparel sector.

Digit ratio (2D:4D) predicts facial, but not voice or body odour, attractiveness in men

There is growing evidence that human second-to-fourth digit ratio (or 2D:4D) is related to facial features involved in attractiveness, mediated by in utero hormonal effects. The present study extends the investigation to other phenotypic, hormone-related determinants of human attractiveness: voice and body odour. Pictures of faces with a neutral expression, recordings of voices pronouncing vowels and axillary odour samples captured on cotton pads worn for 24 h were provided by 49 adult male donors. These stimuli were rated on attractiveness and masculinity scales by two groups of 49 and 35 females, approximately half of these in each sample using hormonal contraception. Multivariate regression analyses showed that males' lower (more masculine) right 2D:4D and lower right-minus-left 2D:4D (Dr−l) were associated with a more attractive (and in some cases more symmetrical), but not more masculine, face. However, 2D:4D and Dr−l did not predict voice and body odour masculinity or attractiveness. The results were interpreted in terms of differential effects of prenatal and circulating testosterone, male facial shape being supposedly more dependent on foetal levels (reflected by 2D:4D ratio), whereas body odour and vocal characteristics could be more dependent on variation in adult circulating testosterone levels.