Facial Expression in First-Impression Judgments of KDEF Faces: Exploratory Observer-Category Effects

We examined how five posed facial expressions relate to self-paced first-impression judgments of attractiveness, trustworthiness, and dominance, and explored moderation by reported participant gender and KDEF model sex. A preliminary study (n = 19) informed stimulus assignment. In the main study, 245 participants recruited through a university course (164 men, 81 women) each rated one photograph of each of 20 KDEF models on 0–5 scales. Across five counterbalanced questionnaire versions, each model was presented in every expression condition. Linear mixed-effects models with random slopes for expression at both the participant and KDEF-model levels showed higher attractiveness for happy than neutral faces (difference, 0.707 points; unadjusted 95% Wald CI [0.533, 0.881]) and higher dominance for angry than neutral faces (difference, 0.780; CI [0.545, 1.015]). Happy faces also received the highest trustworthiness ratings. Cumulative-logit mixed models with crossed random intercepts provided an ordinal sensitivity analysis. Participant-gender and model-sex effects were exploratory and sensitive to the response model and random-effects structure. The findings highlight facial expression as the principal correlate of self-paced first-impression judgments of selected KDEF faces in a university student sample.