Listeners expect that a definite noun phrase with a pre-nominal scalar adjective (e.g., "the big"...) will refer to an entity that is part of a set of objects contrasting on the scalar dimension, e.g., size (Sedivy, Tanenhaus, Chambers, & Carlson, 1999). Two visual world experiments demonstrate that uttering a referring expression with a scalar adjective makes all members of the relevant contrast set more salient in the discourse model, facilitating subsequent reference to other members of that contrast set. Moreover, this discourse effect is caused primarily by linguistic mention of a scalar adjective and not by the listener's prior visual or perceptual experience. These experiments demonstrate that language processing is sensitive to which information was introduced by linguistic mention, and that the visual world paradigm can be use to tease apart the separate contributions of visual and linguistic information to reference resolution. (Contains 2 tables and 13 figures.)