Cohesion, or the connectedness of discourse, has been recognized as playing a crucial role in both language production and comprehension processes. Researchers have debated about the "right" number and classification of cohesive devices, as well as about their interaction with coherence and/or genre. The present study proposes an integrative model of lexical cohesion that extends previous models and argues for the difference between "associative cohesion" and "(lexical) collocation". Its evaluation against a corpus of 14 conversations, 7 broadcast discussions and 7 phone calls, reports the former to show almost six times as many instances of lexical ties as the latter, a difference that is attributed to the divergent features of these two genres. Apart from quantitative findings supported by statistical significance tests, qualitative analyses also show that lexical cohesion is involved in turn-taking behaviors and topic management patterns, thereby contributing to the establishment of interpersonal relationships and the expansion of generic stages in these two kinds of spoken interactions.