Relational Signal Detection: A Multimodal Protocol for Validating Facial, Linguistic, and Behavioural Markers of Light Triad and Dark Tetrad Traits in an Indian Adult Sample

The capacity to detect genuine warmth, prosocial orientation, and relational safety in a potential partner represents one of the most consequential judgment tasks adults navigate. Yet the scientific literature on thin-slice personality judgments has focused disproportionately on threat detection, identifying dark triad and dark tetrad traits, while leaving the positive pole largely unexamined. This paper describes a registered protocol for a cross-sectional study investigating whether multimodal signals routinely available in digital dating contexts carry valid information about both Light Triad traits (Kantianism, Humanism, Faith in Humanity; Kaufman et al., 2019) and dark tetrad traits (narcissism, psychopathy, Machiavellianism, sadism; Paulhus and Williams, 2002), using an Indian adult sample (target N = 500). Automated facial action unit analysis, natural language processing of written bios, and validated psychometric instruments (SD4, LTS, HEXACO-60, ECR-R, RFQ-8) constitute the measurement framework. Three gaps in existing literature are addressed: the near-absence of Indian samples in personality-from-face research, the lack of systematic positive-trait signal detection, and the ecological validity problem inherent in using neutral laboratory photographs rather than self-curated profile images. The protocol is pre-registered on OSF prior to data collection.