In this study, we investigate pauses and durational patterns in Mandarin spontaneous conversation, as well as investigate how reliably such elements can serve as boundary-marking predictors across different types of speech modes and how language activities are affected by their cognitive correlates. Our results show that pause duration is significantly correlated with specific boundary status. We show that the duration elements are a fundamental component of discourse organization in spontaneous speech and simultaneously reflect exigencies of both cognitive processes and interactive communicative exchange.