Previous evidence suggests that when speakers produce sentences from memory or as picture descriptions, their choices of sentence structure are influenced by how easy it is to retrieve sentence material (accessibility). Three experiments assessed whether this pattern holds in naturalistic, interactive dialogue. Pairs of speakers took turns asking each other questions, the responses to which allowed mention of an optional "that" before either repeated (accessible) or unrepeated (inaccessible) material. Speakers' "that" mention was not sensitive to the repetition (accessibility) manipulation. Instead, "that" mention was sensitive to social factors: speakers said "that" more when adopting another's perspective rather than one's own, and tended to say "that" more when attributing emotions to oneself rather than another. A fourth experiment confirmed that in a memory task, the original pattern is observed. These results suggest that "that" mention is sensitive to the cognitive forces that operate within a production task; in dialogue settings, social factors were especially influential. (Contains 5 figures and 1 table.)