The spread of mind: psychological contagion in theory and critique

Psychological contagion (PC) involves the transfer and "snowballing" of emotions, perceptions, or behaviors within or across individuals, often through subtle, automatic, or unconscious mechanisms. This narrative review synthesizes cross-disciplinary evidence and proposes a mechanism-level Cascading-Resonance Model of PC. Drawing on neuroscience, social psychology, media studies, and diffusion theory, we identify nine mechanisms that instantiate a three-layer process involving individual resonance, interpersonal synchronization, and group-level cascade. We summarize empirical patterns across cross-modal domains, map mechanisms to observable indicators and intervention levers, as well as offer falsifiable propositions for measurement and platform-level testing. We further explore the role of contagion in modern-day controversies and anomalous experiences. Findings are preliminary and based on conceptual synthesis rather than exhaustive meta-analysis, so we highlight priority directions for causal, multilevel research and policy evaluation.