In a new study published in the journal Sexes, researchers have uncovered evidence that physical features, particularly breast size, can influence competitive behaviors among women. The study found that women are more likely to engage in derogatory tactics against other women with larger breasts, shedding light on the dynamics of intrasexual competition.
Intersexual competition, a concept grounded in evolutionary biology, refers to the rivalry between individuals of the same sex to attract and secure mates from the opposite sex. This form of competition is driven by the need to enhance reproductive success and pass on genes to the next generation. In humans, intersexual competition manifests in various behaviors and strategies aimed at increasing one’s desirability to potential mates while diminishing the attractiveness of rivals.
While much research has focused on men’s competitive behaviors and the traits they find attractive in potential mates, less attention has been given to how women perceive and react to these traits in each other. The researchers behind the new study were particularly interested in breast morphology—specifically breast size and firmness—given its significance in male mate choice due to associations with fertility and reproductive value.
The researchers recruited 114 predominantly Hispanic women from Texas A&M International University, all of whom identified as heterosexual. The average age of participants was 24 years, and the sample included both single women and those in relationships.
Participants were shown a series of 12 images depicting variations in breast size (A-, B-, C-, and D-cup) and levels of ptosis (no sagging, low sagging, and high sagging). These images, which only showed the lower neck to the upper torso, were manipulated to maintain a consistent intermammary distance (the space between the breasts) to focus solely on size and sagginess variations.
Each participant was asked to rate their likelihood of engaging in verbal and indirect aggression toward the women shown in the images. Verbal aggression included actions like yelling or name-calling, while indirect aggression involved gossiping or spreading rumors.
In addition to rating the images, participants completed the Intrasexual Competition Scale, which measures an individual’s general propensity to compete with others of the same sex.
Women were most likely to engage in rival derogation — verbal and indirect aggression — toward those with D-cup breasts, followed closely by those with C-cup breasts. In contrast, women with A-cup and B-cup breasts were less likely to be targets of such competitive behaviors. This indicates that larger breast sizes, particularly C and D cups, are perceived as greater threats in the context of mate competition.
Interestingly, the researchers found that the level of ptosis did not significantly influence the likelihood of verbal or indirect aggression. This suggests that while breast size is a critical factor in driving competitive behaviors, the firmness or sagginess of the breasts is less impactful in this regard.
Surprising, the researchers did not find a significant correlation between a participant’s dispositional levels of intrasexual competition and their likelihood of engaging in derogation tactics. This could suggest that women’s tendency to compete with other women may be more universally triggered by certain physical traits rather than being strongly influenced by individual differences in competitiveness.
The study’s results align with evolutionary theories suggesting that physical attributes linked to fertility and reproductive value are key drivers of mate competition. Women may perceive those with larger breasts as more attractive to men and therefore more threatening as rivals. This perception triggers competitive behaviors aimed at diminishing the attractiveness and social standing of those perceived as rivals.
But there are some limitations that should be noted. The sample was predominantly Hispanic and drawn from a university population, which may limit the generalizability of the findings to other cultural or age groups. In addition, the study relied on a relatively small set of manipulated images focusing solely on breast size and ptosis, omitting other potentially influential factors like cleavage exposure or clothing.
“Future studies could expand these findings by using a more diverse sample or implementing a cross-cultural comparison,” the researchers wrote, further noting that “there are cross-cultural variations in perceptions of women’s breasts. The current study focused on a primarily Hispanic female sample, for which a previous study showed that larger breasts were considered threatening and were associated with increased intrasexually competitive behavior, but larger breasts are not always perceived as sexually attractive. This warrants further exploration of the cultural dynamics of intrasexual competition and women’s breast morphology.”
The study, “The Role of Breast Morphology in Women’s Rival Derogation Tactics,” was authored by Ray Garza and Farid Pazhoohi.