People at least somewhat agree on what a gullible person looks like; & people whose facial features resemble an expression of anger are perceived as particularly low on gullibility

Who Can Be Fooled? Modeling Facial Impressions of Gullibility. Bastian Jaeger and Erdem O. Meral. Social CognitionVol. 40, No. 2, March 2022. https://doi.org/10.1521/soco.2022.40.2.127

Abstract: The success of acts of deceit and exploitation depends on how trusting and naïve (i.e., gullible) targets are. In three preregistered studies, using both theory-driven and data-driven approaches, we examined how people form impressions of gullibility based on targets' facial appearance. We find significant consensus in gullibility impressions, suggesting that people have a somewhat shared representation of what a gullible person looks like (Study 1, n = 294). Gullibility impressions is based on different cues than trustworthiness or dominance impressions, suggesting that they constitute dissociable facial stereotypes (Study 2, n = 403). Examining a wide range of facial features, we find that gullibility impressions are primarily based on resemblance to an angry facial expression. We also find that young, female, and smiling individuals were seen as more gullible (Study 3, n = 209). These findings suggest that gullibility impressions are based on cues linked to low levels of perceived threat.