The human voice carries information about a vocalizer's physical strength that listeners can perceive and that may influence mate choice and intrasexual competition. Yet, reliable acoustic correlates of strength in human speech remain unclear. Compared to speech, aggressive nonverbal vocalizations (roars) may function to maximize perceived strength, suggesting that their acoustic structure has been selected to communicate formidability, similar to the vocal threat displays of other animals. Here, we test this prediction in two non-WEIRD African samples: an urban community of Cameroonians and rural nomadic Hadza hunter–gatherers in the Tanzanian bushlands. Participants produced standardized speech and volitional roars and provided handgrip strength measures. Using acoustic analysis and information-theoretic multi-model inference and averaging techniques, we show that strength can be measured from both speech and roars, and as predicted, strength is more reliably gauged from roars than vowels, words or greetings. The acoustic structure of roars explains 40–70% of the variance in actual strength within adults of either sex. However, strength is predicted by multiple acoustic parameters whose combinations vary by sex, sample and vocal type. Thus, while roars may maximally signal strength, more research is needed to uncover consistent and likely interacting acoustic correlates of strength in the human voice. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

On average, less than 2% of all Europeans (but 6-13% of population of Ireland, Wales and Scotland) express the redheaded phenotype. [1,2] Mutations in the gene for receptor protein MCIR, the most important regulator of melanogenesis, [3] which is responsible for low levels of eumelanin in the affected subjects, probably spread in human populations after the arrival of modern Homo sapiens to Europe. Nevertheless, the most common allele, Val92Met, seems to have introgressed into our gene pool from Homo neanderthalensis. [4] In redheaded subjects, the eumelanin (black pigment) is, for the most part, substituted with a related pigment pheomelanin (yellow-red pigment) in melanin-containing granules in the skin, hair and iris.

Despite intensive research, evolutionary psychology has not yet reached a consensus regarding the association between sexual dimorphism and attractiveness. This study examines associations between perceived and morphological facial sexual dimorphism and perceived attractiveness in samples from five distant countries (Cameroon, Colombia, Czechia, Iran, and Turkey). We also examined possible moderating effects of skin lightness, averageness, age, body mass, and facial width. Our results suggest that in all samples, women's perceived femininity was positively related to their perceived attractiveness. Women found perceived masculinity in men attractive only in Czechia and Colombia, two distant populations. The association between perceived sexual dimorphism and attractiveness is thus potentially universal only for women. Across populations, morphological sexual dimorphism and averageness are not universally associated with either perceived facial sexual dimorphism or attractiveness. With our exploratory approach, results highlight the need for control of which measure of sexual dimorphism is used (perceived or measured) because they affect perceived attractiveness differently. Morphological averageness and sexual dimorphism are not good predictors of perceived attractiveness. It is noted that future studies should use more population samples to allow for identification of specific effects of local environmental and socioeconomic conditions on preferred traits in unmanipulated local facial stimuli.

Biosocial impact of facial dominance and sex-typicality is well-evidenced in various human groups. It remains unclear, though, whether perceived sex-typicality and dominance can be consistently predicted from sexually dimorphic facial features across populations. Using a combination of multidimensional Bayesian approach and geometric morphometrics, we explored associations between perceived dominance, perceived sex-typicality, measured sexual shape dimorphism, and skin colour in a European and an African population. Unlike previous studies, we investigated the effect of facial variation due to shape separately from variation due to visual cues not related to shape in natural nonmanipulated stimuli. In men, perceived masculinity was associated with perceived dominance in both populations. In European women higher perceived femininity was, surprisingly, likewise positively associated with perceived dominance. Both shape and non-shape components participate in the constitution of facial sex-typicality and dominance. Skin colour predicted perceived sex-typicality in Africans but not in Europeans. Members of each population probably use different cues to assess sex-typicality and dominance. Using our methods, we found no universal sexually dimorphic scale predicting human perception of sex-typicality and dominance. Unidimensional understanding of sex-typicality thus seems problematic and should be applied with cautions when studying perceived sex-typicality and its correlates.

This study examines associations between the dimensions of insecure attachment (anxiety, avoidance) and dyadic adjustment, with a potential mediating effect of conflict communication style. Dyadic analyses and mediation tests were performed on data from 97 Czech and Slovak long-term heterosexual couples. Attachment dimensions were measured by Experiences in Close Relationships-Revised measure (ECR-R-16), six conflict communication styles by the Romantic Partner Conflict Scale (RPCS), and dyadic adjustment by the Dyadic Adjustment Scale (DAS). We confirmed previous findings according to which in both sexes, attachment anxiety and avoidance have a negative effect on dyadic adjustment. We also found that women’s anxiety is negatively associated with their partner’s dyadic adjustment. Our mediation tests showed that in both sexes, the association between attachment anxiety and low dyadic adjustment was partially mediated by a reactive conflict communication style. Moreover, the association between attachment avoidance and low dyadic adjustment in women was partially mediated by both the reactive and compromising communication styles. These results are discussed in the context of behavioral and emotional characteristics of both attachment insecurities and gender differences in interpersonal behavior.