Psychopathic traits alter facial expression of posed and spontaneous smiles, and associated emotional experience

Smiles, as tools for social exchange, rely on both accurate expression and interpretation of emotions. While psychopathy's affective deficits are known, their effect on smiling remains unclear. This study investigates the link between psychopathic traits and facial activity in posed and spontaneous smiling, by assessing the impact on both the expression and of emotion. Employing computer vision (OpenFace) and subjective ratings, we examined smile characteristics (intensity, duration) and emotional experience (valence, arousal) in a sample of 102 individuals who viewed emotionally neutral (control condition) and affective stimuli (spontaneous condition), and received instructions based on imaginary smile-related scenarios (posed condition). Results showed that higher psychopathic trait scores (particularly traits related to affective deficits) were associated with: (1) spontaneous smiles that were longer and more intense, despite being (2) associated with lower self-reported valence, (3) posed smiles that were shorter and less intense, and (4) overall increased self-reported arousal. These findings suggest a nuanced interplay between subclinical variation in psychopathic traits, smiling behaviour, and emotional experience. These findings offer valuable preliminary insights into the potential mechanisms underpinning social functioning in individuals with psychopathic traits.