What tunes accesibility of referring expressions in task-related dialogue?

Ariel (1988) proposes that the grammatical form of anyreferring expression can be predicted from the deemed accessibility of its referent to the intended audience. The term‘deemed’ is critical: it allows the speaker an egocentric perspective and frees choice of expression from the actual contingencies of the situation in which it is uttered. Weanalyze 1775 first mentions of visible objects within a multimodal corpus of cooperative task-related dialogues (Carletta etal., under revision) for effects of situation (communicationmodalities, actions involving the named entity) and of responsibilities assigned to speakers and listeners.Accessibility distributions show statistically significant effects of three kinds: circumstances readily available to the listener(concurrent movement of the named object); circumstances private to the speaker (hovering the mouse over the object,when the listener cannot see the mouse), and speakers’assigned roles.