Interactive Models of Collaborative Communication

The collaborative nature of communication has been demonstrated by research on the increased efficiency (Hupet & Chantraine, 1992) and the adaptive behavior (Giles, Mulac, Bradac, & Johnson, 1987) of interacting pairs, but these two lines of research have never been explicitly related. This paper reports empirical results showing that adaptively matching word use can increase communication efficiency and also gives an ACT-R (Anderson & Lebiere, 1998) modeling account of the processes involved. Efficient Communication Imagine that two people have to communicate a number of times about abstract figures that are difficult to name. Typically, the pair will initially use a long referential phrase and with subsequent references shorten that phrase to one or two words (Clark & Wilkes-Gibbs, 1986; Krauss & Fussell, 1991; Krauss & Weinheimer, 1966). For example, in an experiment run by Krauss and Fussell (1991), a pair shown the figure in Figure 1 referred to it over five trials as a Martini glass with legs on either side Martini glass with the legs Martini glass shaped thing Martini glass Martini Figure 1: An abstract figure This process is evidence of the collaborative nature of communication since subsequent phrases tend to make reference to previous phrases and since the phrase eventually agreed on to describe the object would not likely be able to describe the object without the benefit of the prior history of the evolution of the phrase. Several partner-related factors have been shown to influence the number of words used in the referential communication task. If subjects are asked to create referential phrases for an imagined partner who will later read the phrases, the phrases tend not to decrease over time (Hupet & Chantraine, 1992). If a partner is present but not allowed to give feedback, the rate of decrease is slowed (Krauss & Weinheimer, 1966). Accommodating Communication In this discussion, accommodation is the matching of partner behavior in a conversational setting. These behaviors can include lexical choice (Fais, 1998; Garrod & Anderson, 1987; Garrod & Doherty, 1994) and syntactic choice (Bock, 1986; Fais, 1994) as well as speech styles, dialect, non-verbal behavior, vocal intensity, prosody, speech rate and duration and pause length (Giles, Mulac, Bradac, & Johnson, 1987). Examples of accommodation can be seen in the maze game of Garrod and Doherty (1994), where subjects must decide how to describe their positions in a twodimensional maze. Some subjects came to describe their positions in a line notation, giving first the line and then their location in that line: A: Third row two along. B: Second row three along. Other subjects developed a matrix notation, giving horizontal and vertical locations: A: Correct, I’m presently at C5. B: E1. Most research on accommodation has focused on dependent measures of converging/diverging behavior or recipient evaluations of that behavior. One hypothesis of this paper is that diverging behavior (nonaccommodation) can not only influence the evaluation of behavior, but can also reduce the efficiency of referential communication. Support for this hypothesis would be shorter messages for subjects interacting with accommodating partners as compared to subjects interacting with non-accommodating partners. To do this manipulation with human partners, either confederate partners or partners motivated with positive and negative social group pressures would need to converge or diverge to communication behavior. Either choice would introduce extraneous social complications into a question about informational processing. Ideally, the decision to diverge or converge should be independent of other communication processing in the partner. One solution is to use computational agents as partners. Two agents could be created that would either converge to or diverge from word choice of a human partner, with other communication processing being exactly the same. If both agents accommodated to the message length used by the human partner, then message length could be used as a dependent measure of efficiency. This would then test the effect of lexical accommodation on message length. The generality of the results would be greater if the behavior of the agents were psychologically plausible. One line of research involving computational theory of human cognition is ACT-R. ACT-R & Communication ACT-R (Anderson & Lebiere, 1998) is a computational theory of human cognition incorporating both declarative knowledge (e.g., addition facts) and procedural knowledge (e.g., the process of solving a multi-column addition problem) into a production system where procedural rules act on declarative chunks. At a subsymbolic level, facts have an activation attribute which influences their probability of retrieval and the time it takes to retrieve them. Rules have a reliability attribute which influences their probability of being used. Support for this declarative/procedural viewpoint has been found in many ACT-R language projects. One project emphasizing declarative representation is Boyland and Anderson’s (1997) model of syntactic priming. Research has shown that the use of a specific syntax can be primed in experimental settings if a subject repeats presented sentences (Bock, 1986). Boyland and Anderson created a model that explained this phenomenon as priming of declarative structures built from the comprehension of sentences. With a procedural representation, Matessa and Anderson (2000) showed that the ACT-R rule reliability learning mechanism predicts a blocking effect in cue learning where the use of highly available cues can block the learning of more reliable cues, since the sequential nature of productions allows only one cue to be chosen at a time. This prediction was supported by experimental evidence of blocking for linguistic actor choice cues such as word order, case marking, and verb/noun matching. Taatgen and Anderson (2000) used a model that combined both declarative and procedural learning to explain the Ushaped learning of irregular verbs, and Lewis (1998) created a parsing model with retroactive and proactive interference of declarative knowledge and procedural attachment processes. Any interactive model of communication must be able to establish mutual knowledge, interpret the communicative intent of a partner, follow basic communicative obligations, and use communication to further some goal. These abilities have been the focus of a number of lines of research in the communication literature (Clark & Schaefer, 1989; Core & Allen, 1997; Poesio & Traum, 1998; Traum & Allen, 1994) and the ACT-R model of communication presented in this paper is guided by theories in this literature. ACT-R itself is a method for describing human cognition in terms of facts and rules, but the content of the facts and rules used in communication must be guided by current theories of communication. This model of communication was used to test the effect of accommodation (the matching of partner vocabulary) on communication efficiency by having two ACT-R models created from the basic communication model, one accommodating to word use and one nonaccommodating.