Smelling human sex hormone-like compounds affects face gender judgment of men

Influence of the human body odor compound HMHA on face perception

Body odors convey information about the individuals, but the mechanisms are not fully understood yet. As far as human reproduction is concerned, molecules that are produced in sexually dimorphic amounts could be possible chemosignals. 3-hydroxy-3-methylhexanoic acid (HMHA) is one of them-more typical of men. Here, we investigated the possibility that the perception of gender and attractiveness in human faces could be implicitly influenced by this compound. Clearly feminine, ambiguous and clearly masculine faces were primed with an odor of HMHA, a control odor or air. Based on 100-ms face presentation, 40 raters had to identify the face's gender as quickly as possible and provide attractiveness evaluations. 3-hydroxy-3-methylhexanoic acid tended to be perceived as less pleasant and induced lower sniff duration in women compared with men. As to the effects of HMHA on face perception (vs. control conditions), we found that gender identification and the associated response time were unaffected by HMHA. Attractiveness of the faces, however, increased in presence of HMHA, but not in a sex-specific manner and only for unattractive faces with ambiguous gender. In sum, this study found no evidence in favor of a possible role of this sexually dimorphic compound in intrasexual competition nor in intersexual attraction.

Humans and the Olfactory Environment: A Case of Gene-Culture Coevolution?

As hunter-gatherers, humans used their sense of smell to identify plants and animals, to find their way within a foraging area, or to distinguish each other by gender, age, kinship, or social dominance. Because women gathered while men hunted, the sexes evolved different sensitivities to plant and animal odors. They also ended up emitting different odors. Male odors served to intimidate rival males or assert dominance. With the rise of farming and sedentism, humans no longer needed their sense of smell to find elusive food sources or to orient themselves within a large area. Odors now came from a narrower range of plants and animals. Meanwhile, body odor was removed through bathing to facilitate interactions in enclosed spaces. This new phenotype became the template for the evolution of a new genotype: less sensitivity to odors of wild plants and animals, lower emissions of male odors, and a more negative response to them. Further change came with the development of fragrances to reodorize the body and the home. This new olfactory environment coevolved with the ability to represent odors in the mind, notably for storage in memory, for vicarious re-experiencing, or for sharing with other people through speech and writing.

Investigating the Crossmodal Influence of Odour on the Visual Perception of Facial Attractiveness and Age

We report two experiments designed to investigate whether the presentation of a range of pleasant fragrances, containing both floral and fruity notes, would modulate people’s judgements of the facial attractiveness (Experiment 1) and age (Experiment 2) of a selection of typical female faces varying in age in the range 20–69 years. In Experiment 1, male participants rated the female faces as less attractive when presented with an unpleasant fragrance compared to clean air. The rated attractiveness of the female faces was lower when the participants rated the unpleasant odour as having a lower attractiveness and pleasantness, and a higher intensity. In Experiment 2, both male and female participants rated the age of female faces while presented with one of four pleasant fragrances or clean air as a control. Only the female participants demonstrated a crossmodal effect, with the pleasant fragrances inducing an older rating for female faces in the 40–49-years-old age range, whereas a younger rating was documented for female faces in the 60–69-years-old age range. Taken together, these results are consistent with the view that while the valence of fragrance (pleasant versus unpleasant) exerts a robust crossmodal influence over judgements of facial attractiveness, the effects of pleasant fragrance on judgements of a person’s age appear to be less reliable. One possible explanation for the differing effect of scent in the two cases relates to the fact that attractiveness judgements are more subjective, hedonic, and/or intuitive than age ratings which are more objective, cognitive-mediated, and/or analytic in nature.

Smell what you hardly see: Odors assist visual categorization in the human brain

Visual categorization is the brain ability to rapidly and automatically respond to a certain category of inputs. Whether category-selective neural responses are purely visual or can be influenced by other sensory modalities remains unclear. Here, we test whether odors modulate visual categorization, expecting that odors facilitate the neural categorization of congruent visual objects, especially when the visual category is ambiguous. Scalp electroencephalogram (EEG) was recorded while natural images depicting various objects were displayed in rapid 12-Hz streams (i.e., 12 images / second) and variable exemplars of a target category (either human faces, cars, or facelike objects in dedicated sequences) were interleaved every 9^th stimulus to tag category-selective responses at 12/9 = 1.33 Hz in the EEG frequency spectrum. During visual stimulation, participants (N = 26) were implicitly exposed to odor contexts (either body, gasoline or baseline odors) and performed an orthogonal cross-detection task. We identify clear category-selective responses to every category over the occipito-temporal cortex, with the largest response for human faces and the lowest for facelike objects. Critically, body odor boosts the response to the ambiguous facelike objects (i.e., either perceived as nonface objects or faces) over the right hemisphere, especially for participants reporting their presence post-stimulation. By contrast, odors do not significantly modulate other category-selective responses, nor the general visual response recorded at 12 Hz, revealing a specific influence on the categorization of congruent ambiguous stimuli. Overall, these findings support the view that the brain actively uses cues from the different senses to readily categorize visual inputs, and that olfaction, which has long been considered as poorly functional in humans, is well placed to disambiguate visual information.

Olfaction in the Multisensory Processing of Faces: A Narrative Review of the Influence of Human Body Odors

A recent body of research has emerged regarding the interactions between olfaction and other sensory channels to process social information. The current review examines the influence of body odors on face perception, a core component of human social cognition. First, we review studies reporting how body odors interact with the perception of invariant facial information (i.e., identity, sex, attractiveness, trustworthiness, and dominance). Although we mainly focus on the influence of body odors based on axillary odor, we also review findings about specific steroids present in axillary sweat (i.e., androstenone, androstenol, androstadienone, and estratetraenol). We next survey the literature showing body odor influences on the perception of transient face properties, notably in discussing the role of body odors in facilitating or hindering the perception of emotional facial expression, in relation to competing frameworks of emotions. Finally, we discuss the developmental origins of these olfaction-to-vision influences, as an emerging literature indicates that odor cues strongly influence face perception in infants. Body odors with a high social relevance such as the odor emanating from the mother have a widespread influence on various aspects of face perception in infancy, including categorization of faces among other objects, face scanning behavior, or facial expression perception. We conclude by suggesting that the weight of olfaction might be especially strong in infancy, shaping social perception, especially in slow-maturing senses such as vision, and that this early tutoring function of olfaction spans all developmental stages to disambiguate a complex social environment by conveying key information for social interactions until adulthood.

The scent of attraction and the smell of success: crossmodal influences on person perception

In recent decades, there has been an explosion of research into the crossmodal influence of olfactory cues on multisensory person perception. Numerous peer-reviewed studies have documented that a variety of olfactory stimuli, from ambient malodours through to fine fragrances, and even a range of chemosensory body odours can influence everything from a perceiver's judgments of another person's attractiveness, age, affect, health/disease status, and even elements of their personality. The crossmodal and multisensory contributions to such effects are reviewed and the limitations/peculiarities of the research that have been published to date are highlighted. At the same time, however, it is important to note that the presence of scent (and/or the absence of malodour) can also influence people's (i.e., a perceiver's) self-confidence which may, in turn, affect how attractive they appear to others. Several potential cognitive mechanisms have been put forward to try and explain such crossmodal/multisensory influences, and some of the neural substrates underpinning these effects have now been characterized. At the end of this narrative review, a number of the potential (and actual) applications for, and implications of, such crossmodal/multisensory phenomena involving olfaction are outlined briefly.

Sex differences in main olfactory system pathways involved in psychosexual function

We summarize literature from animal and human studies assessing sex differences in the ability of the main olfactory system to detect and process sex-specific olfactory signals ("pheromones") that control the expression of psychosexual functions in males and females. A case is made in non primate mammals for an obligatory role of pheromonal signaling via the main olfactory system (in addition to the vomeronasal-accessory olfactory system) in mate recognition and sexual arousal, with male-specific as well as female-specific pheromones subserving these functions in the opposite sex. Although the case for an obligatory role of pheromones in mate recognition and mating among old world primates, including humans, is weaker, we review the current literature assessing the role of putative human pheromones (eg, AND, EST, "copulin"), detected by the main olfactory system, in promoting mate choice and mating in men and women. Based on animal studies, we hypothesize that sexually dimorphic effects of putative human pheromones are mediated via main olfactory inputs to the medial amygdala which, in turn, transmits olfactory information to sites in the hypothalamus that regulate reproduction.

Grammatical gender affects gender perception: Evidence for the structural-feedback hypothesis

Two experiments assessed the extent to which grammatical gender provides a predictive basis for bilinguals' judgments about perceptual gender. In both experiments, French-English bilinguals and native English monolinguals were consecutively presented with images of objects manipulated for their (i) conceptual gender association and (ii) grammatical gender category and were instructed to make a decision on a subsequent target face. The experiments differed in the implicitness of the association between the object primes and target faces. Results revealed that when prior knowledge sources such as conceptual gender can be strategically used to resolve the immediate task (Experiment 1), this information was readily extracted and employed. However, grammatical gender demonstrated a more robust and persisting effect on the bilinguals' judgments, indicating that the retrieval of obligatory grammatical information is automatic and modulates perceptual judgments (Experiment 2). These results suggest that grammar enables an effective and robust means to access prior knowledge which may be independent of task requirements.

Processing by the main olfactory system of chemosignals that facilitate mammalian reproduction

This article is part of a Special Issue "Chemosignals and Reproduction". Most mammalian species possess two parallel circuits that process olfactory information. One of these circuits, the accessory system, originates with sensory neurons in the vomeronasal organ (VNO). This system has long been known to detect non-volatile pheromonal odorants from conspecifics that influence numerous aspects of social communication, including sexual attraction and mating as well as the release of luteinizing hormone from the pituitary gland. A second circuit, the main olfactory system, originates with sensory neurons in the main olfactory epithelium (MOE). This system detects a wide range of non-pheromonal odors relevant to survival (e.g., food and predator odors). Over the past decade evidence has accrued showing that the main olfactory system also detects a range of volatile odorants that function as pheromones to facilitate mate recognition and activate the hypothalamic-pituitary-gonadal neuroendocrine axis. We review early studies as well as the new literature supporting the view that the main olfactory system processes a variety of different pheromonal cues that facilitate mammalian reproduction.

Wahrnehmung von Personen und soziale Kognition

Soziale Wahrnehmung, Kommunikation und Interaktion erfordern eine effiziente Analyse und Repräsentation personenbezogener Informationen. Dabei transportieren vor allem Gesichter und Stimmen eine Vielzahl sozial relevanter Informationen, etwa über die Identität einer Person, Emotionen, Geschlecht, Alter, Attraktivität, ethnische Zugehörigkeit oder momentaner Aufmerksamkeitsfokus. Trotz dieses Wissens sind die perzeptuellen Mechanismen der Wahrnehmung komplexer sozialer Stimuli erst in den letzten Jahren systematischer untersucht worden. Diese Entwicklung wurde vorallem durch (1) die Verfügbarkeit sophistizierter Reizmanipulationstechniken (z. B. Bild-, Video- und Stimmen-Morphing, Karikierung, und Mittelungstechniken) sowie (2) die Verfügbarkeit von Messmethoden der kognitiven und sozialen Neurowissenschaften ermöglicht. In diesem Artikel fassen wir den aktuellen Forschungsstand der Wahrnehmung von Personen, besonders bezüglich Gesichter und Stimmen, zusammen. Dabei diskutieren wir ausgewählte Beispiele aktueller Forschung, und legen dar, wie sich die Personenwahrnehmung zu einem zentralen Thema psychologischer Forschung entwickelt hat. Neue Evidenz zeigt, dass sozial relevante perzeptuelle Informationen in Gesichtern oder Stimmen nicht nur erste Eindrücke über Personen erzeugen, sondern dass diese Eindrücke auch moderate Validität aufweisen, so dass Gesichter oder Stimmen als „Fenster zur Person” betrachtet werden können. Wir argumentieren, dass weitere Fortschritte in anderen Feldern der sozialen Kognitionsforschung, welche reale oder virtuelle Agenten berücksichtigen (z. B. Theory of Mind Forschung, soziale Kategorisierung, menschliche Entscheidungen) von einer Berücksichtigung fazialer oder stimmlicher Informationen in der Personenwahrnehmung profitieren.

Hands as sex cues: sensitivity measures, male bias measures, and implications for sex perception mechanisms

Sex perceptions, or more particularly, sex discriminations and sex categorisations, are high-value social behaviours. They mediate almost all inter-personal interactions. The two experiments reported here had the aim of exploring some of the basic characteristics of the processes giving rise to sex perceptions. Experiment 1 confirmed that human hands can be used as a cue to an individual's sex even when colour and texture cues are removed and presentations are brief. Experiment 1 also showed that when hands are sexually ambiguous observers tend to classify them as male more often than female. Experiment 2 showed that "male bias" arises not from sensitivity differences but from differences in response biases. Observers are conservative in their judgements of targets as female but liberal in their judgements of targets as male. These data, combined with earlier reports, suggest the existence of a sex-perception space that is cue-invariant.

What's in a Kiss? The Effect of Romantic Kissing on Mate Desirability

Past research suggests that various courtship rituals, such as romantic kissing, may convey useful mate quality information. Two studies were carried out to examine how purported romantic kissing abilities, as a potential cue to some form of mate information, affect appraisals of potential mating partners. In Experiment 1, 724 participants were presented with vignette descriptions of potential mating partners and were asked to rate partner desirability for various mating-related situations. The primary result of this experiment was that purported kissing ability increased mate desirability in “casual sex” mating situations for women to a greater extent than for men. Experiment 2 repeated the same procedure with another 178 participants, this time including visual information alongside vignette descriptions containing kissing-related information to examine the relative effects of these two modalities. It was found that the presence of a picture alongside a descriptive vignette negated the effect of kissing-related information only when rating potential partners on attractiveness or desirability for further courtship, though not when evaluating partners for casual sex or long-term relationship scenarios. Visual information containing “attractive” photos of potential partners was also found to have a greater effect on men's ratings of partner desirability than on women's ratings of partner desirability. The results are discussed in light of romantic kissing's potential function of conveying important mate quality and desirability information, and its relative role in the presence of additional visual mate cues.

Roles of sex and gonadal steroids in mammalian pheromonal communication

A brain circuit (the accessory olfactory system) that originates in the vomeronasal organ (VNO) and includes the accessory olfactory bulb (AOB) plus additional forebrain regions mediates many of the effects of pheromones, typically comprised of a variety of non-volatile and volatile compounds, on aspects of social behavior. A second, parallel circuit (the main olfactory system) that originates in the main olfactory epithelium (MOE) and includes the main olfactory bulb (MOB) has also been shown to detect volatile pheromones from conspecifics. Studies are reviewed that point to specific roles of several different steroids and their water-soluble metabolites as putative pheromones. Other studies are reviewed that establish an adult, 'activational' role of circulating sex hormones along with sex differences in the detection and/or processing of non-steroidal pheromones by these two olfactory circuits. Persisting questions about the role of sex steroids in pheromonal processing are posed for future investigation.

Adaptation to faces and voices: unimodal, cross-modal, and sex-specific effects

Exposure, or adaptation, to faces or voices biases perceptions of subsequent stimuli, for example, causing faces to appear more normal than they would be otherwise if they are similar to the previously presented stimuli. Studies also suggest that there may be cross-modal adaptation between sound and vision, although the evidence is inconsistent. We examined adaptation effects within and across voices and faces and also tested whether adaptation crosses between male and female stimuli. We exposed participants to sex-typical or sex-atypical stimuli and measured the perceived normality of subsequent stimuli. Exposure to female faces or voices altered perceptions of subsequent female stimuli, and these adaptation effects crossed modality; exposure to voices influenced judgments of faces, and vice versa. We also found that exposure to female stimuli did not influence perception of subsequent male stimuli. Our data demonstrate that recent experience of faces and voices changes subsequent perception and that mental representations of faces and voices may not be modality dependent. Both unimodal and cross-modal adaptation effects appear to be relatively sex-specific.

Sex discriminations made on the basis of ambiguous visual cues can be affected by the presence of an olfactory cue

BACKGROUND

Almost every interpersonal interaction is mediated by the sex of the individuals involved. Visual, auditory, and olfactory cues provide individuals with the opportunity to discriminate the sex of others from a distance and so prepare sex-appropriate behaviours for any impending interaction. The usefulness of that important social skill is mediated by the reliability of the sensory information. Sometimes cues in one domain will be ambiguous, and the perceptual processes mediating sex perceptions will need to integrate information from across the senses for better reliability. With that in mind, the experiment reported here was designed to explore the effect of olfactory-visual interactions on sex perceptions.

METHODS

Observers were presented visually with point-light walkers that were sexually ambiguous (not unequivocally female or male). They were asked to judge, using a two-alternative forced choice paradigm, the sex of each walker. Tested on two occasions, observers unknowingly made sex judgements in the presence or absence of pads soaked in male sweat.

RESULTS

The presence of male sweat was associated with higher proportions of 'male' judgements of both ambiguous female and ambiguous male walkers (F1,19 = 24.11, p < 0.01).

CONCLUSION

These findings suggest that olfactory cues can modulate visual sex discriminations made on the basis of biological motion cues. Importantly, they seem to do so even when the olfactory cue is not consciously perceived, suggesting these effects are mediated by perceptual rather than cognitive processes. These findings suggest that there exist cortical processes mediating sex perceptions that are capable of integrating visual and olfactory information. What is important is that this sensory integration takes place without conscious knowledge and that appropriate behaviour modifications may occur automatically.

Cross-category adaptation: objects produce gender adaptation in the perception of faces

Adaptation aftereffects have been found for low-level visual features such as colour, motion and shape perception, as well as higher-level features such as gender, race and identity in domains such as faces and biological motion. It is not yet clear if adaptation effects in humans extend beyond this set of higher order features. The aim of this study was to investigate whether objects highly associated with one gender, e.g. high heels for females or electric shavers for males can modulate gender perception of a face. In two separate experiments, we adapted subjects to a series of objects highly associated with one gender and subsequently asked participants to judge the gender of an ambiguous face. Results showed that participants are more likely to perceive an ambiguous face as male after being exposed to objects highly associated to females and vice versa. A gender adaptation aftereffect was obtained despite the adaptor and test stimuli being from different global categories (objects and faces respectively). These findings show that our perception of gender from faces is highly affected by our environment and recent experience. This suggests two possible mechanisms: (a) that perception of the gender associated with an object shares at least some brain areas with those responsible for gender perception of faces and (b) adaptation to gender, which is a high-level concept, can modulate brain areas that are involved in facial gender perception through top-down processes.

Neural Correlates of Generic versus Gender-specific Face Adaptation

The perception of facial gender has been found to be adaptively recalibrated: adaptation to male faces causes participants to perceive subsequent faces as more feminine and vice versa [Webster, M. A., Kaping, D., Mizokami, Y., & Duhamel, P. Adaptation to natural facial categories. Nature, 428, 557–561, 2004]. In an event-related brain potential (ERP) study, Kovács et al. [Kovács, G., Zimmer, M., Banko, E., Harza, I., Antal, A., & Vidnyanszky, Z. Electrophysiological correlates of visual adaptation to faces and body parts in humans. Cerebral Cortex, 16, 742–753, 2006] reported reduced N170 amplitudes and increased latencies for test faces following female gender adaptation compared to control stimulus (a phase randomized face) adaptation. We examined whether this N170 attenuation to test faces was related to the adaptor's gender, or to adaptation to face exposure in general. We compared N170 effects after adaptation to either male or androgynous faces. Additionally, we investigated cross-modal adaptation for the same test faces following male or androgynous voice adaptors. Visual adaptation to face gender replicated previously reported aftereffects in classifying androgynous faces, and a similar trend was observed following adaptation to voice gender. Strikingly, N170 amplitudes were dramatically reduced for faces following face adaptors (relative to those following voice adaptors), whereas only minimal gender-specific adaptation effects were seen in the N170. By contrast, strong gender-specific adaptation effects appeared in a centroparietal P3-like component (∼400–600 msec), which in the context of adaptation may reflect a neural correlate of the detection of perceptual novelty.

Can anchor models explain inverted-U effects in facial judgments?

Researchers in a variety of disciplines have found that participants take less time and generate less diversity of responses when judging stimuli towards the ends of a scale than when judging those near the center. Three types of models, connectionist, exemplar, and anchor models, can account for these inverted-U effects. Anchor models assume that stimuli near the ends of the scale are used as anchors to compare with the other stimuli, implying that anchor representations are activated for each judgment. Therefore, participants should learn the anchors better than the other stimuli. Participants were 40 students from the Department of Psychology at McGill University (5 men; M age = 20.5 yr.; SD = 1.7). The experiment involved two tasks: first participants judged facial gender and then performed a recognition task. The results showed no correlation between the position on the gender scale and recognition accuracy. Several hypotheses were offered to explain these results.

Asymmetries of the human social brain in the visual, auditory and chemical modalities

Structural and functional asymmetries are present in many regions of the human brain responsible for motor control, sensory and cognitive functions and communication. Here, we focus on hemispheric asymmetries underlying the domain of social perception, broadly conceived as the analysis of information about other individuals based on acoustic, visual and chemical signals. By means of these cues the brain establishes the border between 'self' and 'other', and interprets the surrounding social world in terms of the physical and behavioural characteristics of conspecifics essential for impression formation and for creating bonds and relationships. We show that, considered from the standpoint of single- and multi-modal sensory analysis, the neural substrates of the perception of voices, faces, gestures, smells and pheromones, as evidenced by modern neuroimaging techniques, are characterized by a general pattern of right-hemispheric functional asymmetry that might benefit from other aspects of hemispheric lateralization rather than constituting a true specialization for social information.

Sensory dominance in combinations of audio, visual and haptic stimuli

Participants presented with auditory, visual, or bi-sensory audio-visual stimuli in a speeded discrimination task, fail to respond to the auditory component of the bi-sensory trials significantly more often than they fail to respond to the visual component--a 'visual dominance' effect. The current study investigated further the sensory dominance phenomenon in all combinations of auditory, visual and haptic stimuli. We found a similar visual dominance effect also in bi-sensory trials of combined haptic-visual stimuli, but no bias towards either sensory modality in bi-sensory trials of haptic-auditory stimuli. When presented with tri-sensory trials of combined auditory-visual-haptic stimuli, participants made more errors of responding only to two corresponding sensory signals than errors of responding only to a single sensory modality, however, there were no biases towards either sensory modality (or sensory pairs) in the distribution of both types of errors (i.e. responding only to a single stimulus or to pairs of stimuli). These results suggest that while vision can dominate both the auditory and the haptic sensory modalities, it is limited to bi-sensory combinations in which the visual signal is combined with another single stimulus. However, in a tri-sensory combination when a visual signal is presented simultaneously with both the auditory and the haptic signals, the probability of missing two signals is much smaller than of missing only one signal and therefore the visual dominance disappears.

Subthreshold amounts of social odorant affect mood, but not behavior, in heterosexual women when tested by a male, but not a female, experimenter

Previously, we have demonstrated that exposure to the endogenous steroid androstadienone has the ability to modulate women's mood in that they feel more focused [Lundstrom, J.N., Goncalves, M., Esteves, F., Olsson, M.J., 2003a. Psychological effects of subthreshold exposure to the putative human pheromone 4,16-androstadien-3-one. Hormones and Behaviour 44 (5), 395-401]. Here, we tested the hypothesis that androstadienone exposure would modulate participating women's mood and corresponding behavior as measured by a sustained attention task. Thirty-seven women participated in a double-blind, within-group experiment and were tested by either a female or a male experimenter. Effects on mood, psychophysiological arousal, sustained attention, and ratings of male facial attractiveness were assessed. Sensory detection of the experimental substance was rigorously controlled for by psychophysical testing. The results showed that exposure to a non-detectable amount of androstadienone modulated women's psychophysiological arousal and mood in a positive direction but did not change attention performance or rating of facial attractiveness. Moreover, mood effects were only evident when an experimenter of the opposite sex conducted the testing. This suggests that social context is important for mood effects of androstadienone exposure in women.