Trust formation is an important psychological process that shapes cooperation, communication, and relationship development within newly formed groups. During early interactions, individuals develop expectations about other group members based on limited information, past experiences, and social signals. When actual behaviours differ from these expectations, individuals experience social prediction errors and must adjust their judgments and trust levels. The present Social Psychology Research Article examines the relationship between social prediction errors and trust adjustment in newly formed groups. The study explores how unexpected positive or negative behaviours influence perceptions of reliability, willingness to cooperate, and future interaction intentions among group members. The proposed framework considers social prediction errors as cognitive experiences that encourage individuals to evaluate and update their beliefs about others. When group members encounter behaviours that do not match their expectations, they may revise their impressions and modify their level of trust. The research focuses on behavioural indicators including trust adjustment, cooperation tendency, member evaluation, and social confidence. This study contributes to social psychology by connecting social cognition processes with interpersonal trust development. Understanding how people adjust trust after unexpected social experiences may provide insights into teamwork, group formation, educational collaboration, and workplace relationships.