Evolutionarily Stable Communication and Pragmatics

In the past 20 or so years there has been much research interest in the evolution of cooperation in humans (Axelrod, 1995; Boyd & Richerson, 1992; Fehr & Fischbacher, 2003; Milinski et al., 2002; West et al., 2006). The foundational problem addressed by this work is how cooperation can remain evolutionarily stable when individuals have incentives to freeride; that is, to take but not contribute from the public good (Hardin, 1968). There is an analogous problem associated with the evolution of communication: how can signalling remain evolutionarily stable when individuals have incentives to be dishonest? This gametheoretic question is the defining problem of animal signalling theory (Maynard Smith & Harper, 2003; Searcy & Nowicki, 2007). The main goals of this chapter are to explore the various possible solutions to this problem and to ask which most likely applies to human communication. In addition to this it will also, using insights from pragmatics, provide some insight as to the nature of the problem and hence clarify some of the relevant issues. It is somewhat remarkable that the question of the evolutionary stability of human communication has historically received little interest relative to the attention given to the evolution of cooperation and the burgeoning literature on the evolution of language. In the last 15–20 years both have expanded dramatically. Language evolution in particular has grown from a niche interest into a well-recognised academic discipline in its own right, with regular conferences, an ever-increasing number of papers on the topic (Google Scholar returns1 13,800 hits for the search language evolution in 1990, increasing almost monotonically to 54,400 in 2005), and special issues of relevant journals (e.g. Lingua, volume 117(3), 2007; Interaction Studies, volume 9(1), 2008). It would be reasonable to assume that solutions to the problem of evolutionarily stable communication in humans would be a central explanandum for such a discipline, but that is not the case: very few papers have made this question a central focus (exceptions include Knight, 1998; Lachmann et al., 2001; Scott-Phillips, 2008; Szmad & Szathmry, 2006). There has thus been only limited progress beyond speculative discussion, and the contrast with developments in the evolution of cooperation is striking. This chapter begins with the observation that although there are important equivalences between the problems of cooperation and communication, it can be misleading to think about the latter exclusively in terms of the former, as that masks the fact that there are in fact two problems associated with the