Even small differences in attractiveness and formidability affect the probability and speed of selection: An online study and an offline replication

Facial and bodily features represent salient visual stimuli upon which people spontaneously attribute various fitness-relevant characteristics such as attractiveness or formidability. While existing evidence predominantly relies on sequential stimuli presentation tasks, real-world social comparisons often involve assessing two or multiple individuals. In studies using two-alternative forced-choice tasks, participants usually perform at rates above the chance to select the expected option. However, these tasks use dichotomized and artificially manipulated stimuli that lack generalizability in situations where the differences between individuals are less likely to be ‘clear-cut’. We tested whether the probability of selection will proportionally increase with increasing degrees of difference between the stimuli or whether there is a discrimination threshold if the stimuli are perceived as too similar. In two registered studies comprising online (N = 446) and onsite (N = 56) participants, we explored the influence of the degree of difference in attractiveness and formidability ratings between stimuli pairs on both the probability of selection and selection speed. Participants were presented with randomly selected pairs of men (30 pairs of faces, 30 pairs of bodies) and tasked with choosing the more attractive or formidable target. Applying Bayesian inference, our findings reveal a systematic impact of the degree of difference on both the selection probability and speed. As differences in attractiveness or formidability increased, both men and women exhibited a heightened propensity and speed in selecting the higher-scoring stimuli. Our study demonstrates that people discriminate even slight differences in attractiveness and formidability, indicating that cognitive processes underlying the perception of these characteristics had undergone natural selection for a high level of discrimination.