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

Version 1.3: Three methodological gap fixes added - DAI formula rationale, ACS weight rationale with sensitivity analysis plan, and explicit Benjamini-Hochberg FDR specification. No hypotheses or primary analyses changed.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.