Drawing on the evolutionary theory of loneliness, this dissertation explores how hypervigilance during communication contributes to social isolation for those with elevated social anxiety. The primary objective is to determine how prosocial communication affects social withdrawal behavior over time and to examine the mechanisms by which social anxiety exacerbates loneliness during moment-to-moment interactions. This dissertation begins with an exploration of the etiological foundations of social anxiety, establishing it as a stable, trait-like predictor rooted in childhood behavioral inhibition. A theoretical model is proposed, describing the relationship among social anxiety, hypervigilance during communication, and social connection. The model posits that individuals with elevated trait social anxiety are predisposed to various forms of isolation, which results in heightened vigilance during social interactions and ultimately influences both the processing and production of communication messages.