Recent research sheds light on how the shoulder-to-hip ratio influences perceptions of attractiveness at the neural level. The study, published in the Archives of Sexual Behavior, uncovered pronounced brain activity variations related to male upper body size, but less pronounced differences when evaluating women, emphasizing the evolutionary importance of men’s upper body size in attractiveness judgments.
The researchers conducted this study to investigate how upper body size, specifically the shoulder-to-hip ratio, affects the neurophysiological and behavioral responses related to perception and attractiveness in both male and female body figures. Men and women tend to find individuals with larger upper bodies more attractive due to associations with masculinity, immune system strength, and other qualities. However, there was limited understanding of how these associations are reflected in brain activity.
“While there have been studies on the neural correlates of facial attractiveness, in the current study, we examined for the first time how upper body size modulates neurophysiological correlates relevant to perception and attractiveness,” said study author Farid Pazhoohi, a lecturer in psychology at the University of Plymouth.
“Specifically, in this study we investigated the impact of shoulder-to-hip ratio, the circumference of the shoulders relative to the hips, on attractiveness judgments of male and female body figures. Shoulder-to-hip ratio is a sexually dimorphic trait in humans, and is an indicator of men’s attractiveness for both men and women.”
The study included 48 participants (28 females) aged between 18 and 37 who were recruited from the University of Minho. To gather data, participants completed questionnaires to collect sociodemographic information and undertook two distinct tasks: an oddball task and an attractiveness judgment task.
In the oddball task, participants were presented with avatars of varying shoulder-to-hip ratio and were instructed to press a key when they detected the presence of flowers on a T-shirt, serving as an infrequent “oddball” event. In contrast, the attractiveness judgment task involved participants rating the attractiveness of avatars with different shoulder-to-hip ratio on a 7-point Likert scale.
The researchers employed DAZ 3D Studio software to generate the avatars, producing six variations for each sex by manipulating the shoulder-to-hip ratios to represent small, medium, and large ratios. These shoulder-to-hip ratios were based on previously established measurements for men.
Irrespective of the participants’ gender, there was a unanimous preference for avatars with larger shoulder-to-hip ratios. In other words, both male and female participants rated both the male and the female avatars with larger shoulder-to-hip ratios as more attractive compared to the avatars with smaller shoulder-to-hip ratios.
The researchers employed EEG (electroencephalogram) analysis as a means to delve deeper into the neurological mechanisms underlying the judgments of attractiveness. EEG is a non-invasive method used to record electrical activity in the brain, providing valuable insights into brain responses.
The study focused on what are referred to as “temporal factors” (TFs) derived from the EEG data. These TFs represent specific patterns of electrical activity in the brain over time, allowing researchers to pinpoint when and how the brain responds to various stimuli.
In the oddball task, the EEG analysis revealed that male avatars with larger shoulder-to-hip ratios triggered more pronounced negative neural responses in a specific temporal factor, namely TF5. This suggests that when participants observed male avatars with larger shoulder-to-hip ratios, certain brain regions associated with processing visual information and perhaps emotional responses exhibited more active negative responses.
Additionally, the researchers used LORETA analysis, a specialized technique that helps identify the specific brain regions responsible for these electrical activities. They found higher activation in the right postcentral gyrus when participants were exposed to male avatars with large shoulder-to-hip ratios compared to those with medium shoulder-to-hip ratios (as identified in TF4). The postcentral gyrus is associated with processing sensory information from the body, suggesting that larger shoulder-to-hip ratios in male avatars may have triggered more sensory processing in this region.
In the attractiveness judgment task for male avatars, the EEG analysis indicated that small shoulder-to-hip ratios elicited more negative neural responses compared to medium shoulder-to-hip ratios, and this was evident in TF5. Similarly, LORETA analysis showed differences in brain activity, with higher activation in the right cuneus when participants rated male avatars with small shoulder-to-hip ratios compared to medium shoulder-to-hip ratios(as identified in TF3). The cuneus is associated with processing visual information, indicating that smaller shoulder-to-hip ratios may have led to heightened visual processing in this brain region.
Interestingly, when it came to female avatars, no significant differences in neural responses were observed for either the oddball task or the attractiveness judgment task. This suggests that the neural processing of attractiveness judgments may differ between male and female avatars. These findings highlight the potential for gender-specific neural responses in the context of attractiveness judgments, adding a layer of complexity to our understanding of how the brain perceives and evaluates physical attributes like the shoulder-to-hip ratio.
“While the behavioral findings revealed that both men and women found larger upper body sizes more attractive in both male and female avatars compared to smaller ones, the EEG results, indicated that brain activity associated with male upper body size varied depending on specific proportions, both in early and late processing stages,” Pazhoohi told PsyPost. “However, differences in neural activity related to female upper body size were less prominent.”
“In simpler terms, while brain activity differences related to male avatars’ upper body size were evident both on the surface and deep within the brain, those related to female avatars’ upper body size were only observable in deep brain activity and within a narrower timeframe than observed for males. This research, the first of its kind to explore brain activity in response to upper body size perception, underscores the evolutionary significance of men’s upper body size compared to women’s at the neural level.
“Our finding at the neural level corroborates the previous findings that men and women find men (but presumably not women) with larger upper bodies more attractive as such a trait in men is associated with qualities like masculinity and a strong immune system as well as fighting ability, formidability and ability to gain access to resources,” Pazhoohi explained.
The study, “Neural Correlates and Perceived Attractiveness of Male and Female Shoulder‑to‑Hip Ratio in Men and Women: An EEG Study“, was authored by Farid Pazhoohi, Joana Arantes, Alan Kingstone, and Diego Pinal.