Memory Representations Supporting Speakers' Choice of Referring Expression: Effects of Category Overlap and Shared Experience.

Memory Representations Supporting Speakers’ Choice of Referring Expression: Effects of Category Overlap and Shared Experience Kristen Skovbroten Gorman (ksgorman@bcs.rochester.edu) Whitney Gegg-Harrison (wgharrison@bcs.rochester.edu) Chelsea R. Marsh (chelsea.marsh@rochester.edu) Michael K. Tanenhaus (mtan@bcs.rochester.edu) Department of Brain & Cognitive Sciences, University of Rochester Rochester, NY 14607 USA Abstract Speakers must take their addressee’s knowledge into account in choosing to refer to an object using a name or a description. Do speakers keep track of partner-specific information about the common ground status of names? And if so, what mechanisms support this ability? We present a series of experiments that investigate the nature of the memory representations involved in supporting speakers’ ability to distinguish shared from privileged information. The results of these experiments suggest that category information can be used as a cue to aid retrieval of ground status, and that shared experience plays an important role in helping speakers to distinguish privileged information from shared information. Keywords: language production; common ground; memory representations; referring expressions; shared experience. Introduction One of the most basic things we do with language is use it to refer to a particular object or individual in the world. In order to successfully refer, speakers must choose a referring expression that is likely to be understood by their addressees. One of the decisions that speakers face is whether to use a name (e.g. Inta) or a description (e.g. the yellow thing that looks like a worm). A name will be the shorter and more precise referring expression, but only if the addressee knows the name. The distinction between names and descriptions has been especially significant within the domains of philosophy of language, semantics, and pragmatics, due to debates about the nature of their meanings and the means by which they refer. Though some (e.g. Searle, 1950) have argued that names are simply shorthand for sets of descriptions and thus refer similarly, more widely accepted accounts (following Kripke, 1980) hold that names like John do not carry any descriptive content which addressees could use to ascertain the reference; instead, they refer directly, by virtue of having a special connection to the referent. Thus a name tells an addressee which thing is being picked out by the speaker, but does not tell them anything about it. In their account of reference in interactive dialog, Clark and Wilkes-Gibbs (1992) describe the process involved in successful reference as a collaboration between speaker and addressee. They examine conversations in which speakers and addressees must work together to arrange a set of cards printed with complex “tangram” figures, and find that over the course of these conversations, speakers and addressees seem to work together to establish mutually acceptable referring expressions, often starting with descriptions and eventually entraining upon shorter, more name-like expressions. Subsequent studies have shown that these shortened expressions are difficult to understand for individuals who did not participate in the collaborative process, lending further credence to the view that successful reference requires coordination during conversation (Clark & Shober, 1992). Notions of common ground, coordination, and perspective-taking are central to understanding reference in interactive conversation, and for developing dialog systems that can successfully interact with human users using natural language (e.g. Brennan 2000), and are particularly important for understanding the difference between a name and description. In order to understand a name, the addressee needs to know that the name is linked to the particular referent, and in order to felicitously use a name to refer to an object, the speaker must believe that their addressee has that knowledge; thus, in order to successfully refer using a name, interlocutors must have some way of establishing and representing what knowledge is shared with their conversational partner. Clark and Marshall (1978) provide an account of this process in which interlocutors build up detailed representations of shared knowledge over the course of conversation; speakers then use these detailed “reference diaries” in deciding what to say. However, many have argued that the process of building up and maintaining such detailed representations may be too computationally intensive to realistically account for what happens during ordinary conversation (e.g. Keysar, Lin & Barr, 2003). Because speakers’ use of names provides a window into their beliefs regarding their addressee’s knowledge, names are a valuable tool for investigating our abilities for perspective-taking and representing common ground. Recent work involving name usage has begun to explore the limits on these abilities, and what those limits might tell us about the nature of the processes and representations involved. For example, Wu and Keysar (2007) argue that instead of tracking whether or not individual pieces of knowledge are shared with a particular addressee, speakers might instead use a global Information Overlap Heuristic. Using such a heuristic, speakers could safely assume that they could rely on their own knowledge when the overlap in