Waist to hip ratio and breast size modulate the processing of female body silhouettes: An EEG study

Aging amplifies sex differences in low alpha and low beta EEG oscillations

Biological sex profoundly shapes brain function, yet its precise influence on neural oscillations was poorly understood. Despite decades of research, studies investigating sex-based variations in electroencephalographic (EEG) signals have yielded inconsistent findings that obstructs what may be a potentially crucial source of inter-individual variability in brain function. To address this, we analyzed five publicly available resting-state datasets, comprising EEG data (n = 445) and iEEG data (n = 103). Three age ranges were defined, young adult (YA, 18-30 years), middle-aged adult (MA, 30-55 years) and older adult (OA, 55-80 years). Our results revealed striking age-dependent sex differences: OA group exhibited robust sex differences, with males showing heightened low alpha (8-9 Hz) activity in temporal regions and attenuated low beta (16-20 Hz) oscillations in parietal-occipital areas compared to females. Intriguingly, these sex-specific patterns were absent in YA group, suggesting a complex interplay between sex and aging in shaping brain dynamics. The MA groups fall in between YA and OA group. The increase of low beta band activity in older female adults is strongly associated with hip size and BMI. Furthermore, we identified consistent sex-related activity in the precentral gyrus with the results of scalp EEG, potentially driving the observed scalp EEG differences. This multi-level analysis allowed us to bridge the gap between cortical and scalp-level observations, providing a more comprehensive picture of sex-related neural dynamics. The distinct associations between sex-specific oscillatory patterns and several lifestyle factors demonstrates the complex interplay between sex, age, and neural oscillations, revealing the variability in brain dynamics. Our findings highlight the importance of careful demographic consideration in EEG research design to ensure fairness in capturing the full spectrum of neurophysiological diversity.

Curviness is a better predictor of a woman's body attractiveness than the waist-to-hip ratio

The waist-to-hip ratio (WHR) is commonly used as an indicator of mid-body fat distribution and is often used to answer health-related questions. It has also been suggested that a woman's WHR can signal her reproductive fitness. This notion is supported by evidence indicating a relation between WHR and a woman's physical attractiveness. However, it was also acknowledged that the actual fitness cue is the curviness of a woman's body. While curviness is easy to perceive, it is difficult to quantify. Therefore, the WHR is often considered as a simple measure of body curviness. However, the WHR and curviness are not uniquely related. After replicating results of a pioneering study in this area, we therefore tested whether the WHR or curviness better predicts a woman's physical attractiveness. As stimuli, we used simple line drawings of women's bodies, differing in their curviness and width. The results demonstrate that curviness is a better predictor, even though we used a relatively simple curvature-based measure of curviness. This outcome indicates that the WHR is a poor measure of a woman's body curviness and underscores the need for a more accurate measure of curviness when assessing the physical attractiveness of a woman's body.

Neural Correlates and Perceived Attractiveness of Male and Female Shoulder-to-Hip Ratio in Men and Women: An EEG Study

While there are studies regarding the neural correlates of human facial attractiveness, there are few investigations considering neural responses for body form attractiveness. The most prominent physical feature defining men's attractiveness is their physical fitness and upper body strength. Shoulder-to-hip ratio (SHR), a sexually dimorphic trait in humans, is an indicator of men's attractiveness for both men and women. The current study is the first to report on the neurophysiological responses to male and female body forms varying in SHR in healthy heterosexual men and women observers. Electroencephalographic (EEG) signals were acquired while participants completed an oddball task as well as a subsequent attractiveness judgement task. Behavioral results showed larger SHRs were considered more attractive than smaller SHRs, regardless of stimuli and participants' sex. The electrophysiological results for both the oddball task and the explicit judgement of attractiveness showed that brain activity related to male SHR body stimuli differed depending on the specific ratios, both at early and late processing stages. For female avatars, SHR did not modulate neural activity. Collectively the data implicate posterior brain regions in the perception of body forms that differ in attractiveness vis-a-vis variation of SHR, and frontal brain regions when such perceptions are rated explicitly.

The Interacting Effects of Height and Shoulder-to-Hip Ratio on Perceptions of Attractiveness, Masculinity, and Fighting Ability: Experimental Design and Ecological Validity Considerations

Previous research has shown that men's height and upper body size are both associated with the perception of attractiveness, because they might be cues to men's genetic fitness, fighting ability, and resource holding power. However, the combined effects of men's height and upper body size have not been explored. In this research, across four studies (N = 659 heterosexual women), we systematically explored the perception of men's muscular upper body at different heights on perceptions of attractiveness, masculinity, and fighting ability. Women rated male stimuli with heights ranging from 160 cm (5'3″) to 190 cm (6'3″) and three values of shoulder-to-hip ratio (SHR). In general, results showed that women considered taller men and men with larger SHR as more attractive, masculine, and better in fighting ability. However, a robust interaction between height and SHR was dependent on participants being exposed to variation on both variables and the ecological validity of the stimuli (silhouettes vs. more realistic rendered figures).

Physical Disability Affects Women's but Not Men's Perception of Opposite-Sex Attractiveness

Physical appearance influences our perceptions, judgments, and decision making about others. While the current literature with regard to the perceptions and judgments of nondisabled people’s attractiveness is robust, the research investigating the perceived physical attractiveness and judgments of physically disabled individuals is scarce. Therefore, in the current study, we investigated whether people with physical disabilities are perceived by the opposite sex as more or less attractive relative to nondisabled individuals. Our results, based on over 675 participants, showed a positive effect for women’s attractiveness ratings of men with physical disabilities, but not men’s attractiveness ratings of physically disabled women. Moreover, social desirability bias was positively associated with attractiveness ratings of physically disabled individuals, meaning those with higher tendency to be viewed favorably by others rated physically disabled individuals more attractive. Finally, our results revealed that attractiveness ratings of individuals with physical disabilities are positively associated with extroversion and empathy in both men and women, and positively with agreeableness and negatively with neuroticism in women. In conclusion, our study showed women rate men with physical disabilities as higher on attractiveness than nondisabled men, which is also influenced by their social desirability bias.