Language Evolution and Computation Bibliography

How communication systems emerge is a topic of relevance to several academic disciplines. Numerous existing models, both mathematical and computational, study this emergence. However, with few exceptions, these models all build some form of communication into their initial specification. Consequently, what these models study is how communication systems transition from one form to another, and not how communication itself emerges in the first place. Here we present a new computational model of the emergence of communication which, unlike previous models, does not pre-specify the existence of communication. We conduct two experiments using this model, in order to derive general statements about how communication systems emerge. The two main routes to communication that we identify correspond with findings from the empirical literature on the evolution of animal signals. We use this finding to explain when and why we should expect communication to emerge in nature. We also compare our model to experimental research on the origins of human communication systems, and hence show that humans are an important exception to the general trends we observe. We argue that this is because humans, and probably only humans, are able to ‘signal signalhood’, i.e. to express communicative intentions.

Communication involves a pair of behaviours—a signal and a response—that are functionally interdependent. Consequently, the emergence of communication involves a chicken-and-egg problem: if signals and responses are dependent on one another, then how does such a relationship emerge in the first place? The empirical literature suggests two solutions to this problem: ritualization and sensory manipulation; and instances of ritualization appear to be more common. However, it is not clear from a theoretical perspective why this should be the case, nor if there are any other routes to communication. Here, we develop an analytical model to examine how communication can emerge. We show that: (i) a state of non-interaction is evolutionarily stable, and so communication will not necessarily emerge even when it is in both parties' interest; (ii) the conditions for sensory manipulation are more stringent than for ritualization, and hence ritualization is likely to be more common; and (iii) communication can arise by a third route, when the intention to communicate can itself be communicated, but this may be limited to humans. More generally, our results demonstrate the utility of a functional approach to communication.

Communication is a fundamentally interactive phenomenon. Evolutionary biology recognises this fact in its definition of communication, in which signals are those actions that cause reactions, and where both action and reaction are designed for that reason. Where only one or the other is designed then the behaviours are classed as either cues or coercion. Since mutually dependent behaviours are unlikely to emerge simultaneously, the symmetry inherent in these definitions gives rise to a prediction that communication will only emerge if cues or coercive behaviours do so first. They will then be co-opted for communication. A range of case studies, from animal signalling, evolutionary robotics, comparative psychology, and evolutionary linguistics are used to test this prediction. The first three are found to be supportive. However in the Embodied Communication Game, a recent experimental approach to the emergence of communication between adult humans, communication emerges even when cues or coerced behaviours are not possible. This suggests that humans are exceptional in this regard. It is argued that the reason for this is the degree to which we are able and compelled to read and interpret the behaviour of others in intentional terms.

A naive observer would be forgiven for assuming that the field of language evolution would, in terms of its scope and methodologies, look much like the field of evolutionary psychology, but with a particular emphasis on language. However, this is not the case. This editorial outlines some reasons why such a research agenda has not so far been pursued in any large-scale or systematic way, and briefly discusses one foundational aspect of that agenda, the question of evolutionary function. This background provides context for an introduction of the articles that appear in this special issue on the evolution of language.

The historical origins of natural language cannot be observed directly. We can, however, study systems that support language and we can also develop models that explore the plausibility of different hypotheses about how language emerged. More recently, evolutionary linguists have begun to conduct language evolution experiments in the laboratory, where the emergence of new languages used by human participants can be observed directly. This enables researchers to study both the cognitive capacities necessary for language and the ways in which languages themselves emerge. One theme that runs through this work is how individual-level behaviours result in population-level linguistic phenomena. A central challenge for the future will be to explore how different forms of information transmission affect this process.

A unique hallmark of human language is that it uses signals that are both learnt and symbolic. The emergence of such signals was therefore a defining event in human cognitive evolution, yet very little is known about how such a process occurs. Previous work provides some insights on how meaning can become attached to form, but a more foundational issue is presently unaddressed. How does a signal signal its own signalhood? That is, how do humans even know that communicative behaviour is indeed communicative in nature? We introduce an experimental game that has been designed to tackle this problem. We find that it is commonly resolved with a bootstrapping process, and that this process influences the final form of the communication system. Furthermore, sufficient common ground is observed to be integral to the recognition of signalhood, and the emergence of dialogue is observed to be the key step in the development of a system that can be employed to achieve shared goals.

Pragmatics is the branch of linguistics that addresses the relationship between language and its external environment `` in particular the communicative context. Social evolution (or sociobiology) is the branch of the biological sciences that studies the social behaviour of organisms, particularly with respect to the ecological and evolutionary forces with which it must interact. These two disciplines thus share a natural epistemic link, one that is concerned with the relationship between behaviour and the environment. There has, however, historically been no dialogue between them. This thesis attempts to fill that void: it examines pragmatics from the perspective of social evolution theory. Chapter 1 gives a brief introduction to the two fields and their key ideas, and also discusses why an evolutionary understanding of pragmatics is crucial to the study of language origins.

In chapter 2 the vexed question of the biological function of language is discussed. Responses are given to the claims, common in the evolutionary linguistics literature, that the processes of exaptation, self organisation and cultural transmission provide alternatives to natural selection as a source of design in nature. The intuitive conclusion that the function of language is communication is provisionally supported, subject to a proper definition of communication.

Chapter 3 reviews previous definitions and consequently argues for an account predicated on the designedness of signals and responses. This definition is then used to argue that an evolutionarily coherent model of language should recognise the pragmatic realities of ostension and inference and reject the code like idealisation that is often used in its place.

Chapter 4 observes that this fits the argument that the biological function of language is communication and then addresses the key question faced by all evolved communication systems `` that of evolutionary stability. The human capacity to record and remember the past behaviour of others is seen to be critical.

Chapter 5 uses the definition of communication from chapter 3 to describe a very general model of evolved communication, and then uses the constraints of that model to argue that Relevance Theory, or at least some theory of pragmatics with a very similar logical structure, must be correct.

Chapter 6 then applies the theoretical apparatus constructed in chapters 2 to 5 to a crucial and topical issue in evolutionary linguistics: the emergence of learnt, symbolic communication. It introduces the Embodied Communication Game, an experimental tool whose basic structure is significantly informed by both social evolutionary and, in particular, pragmatic theory. The novelty of the game is that participants must find a way to communicate not just the content that they wish to convey, but also the very fact that a given behaviour is communicative in nature, and this constraint is found to fundamentally influence the type of system that emerges.

Chapter 7, which concludes the thesis, recounts and clarifies what it tells us about the origins and evolution of language, and suggests a number of possible avenues for future research.

Communication is ubiquitous in biology, and agreement on terms essential for scientific progress. Yet there is no agreed definition of biological communication. Definitions couched in terms of adaptation are often used, but there is significant variability in exactly which criteria are invoked. An alternative is to define communication in terms of information transfer. This article reviews the merits of these approaches, and argues that the former is to be preferred, so long as we demand that both the signal and the response be adaptive, rather than just one or the other, as is common. Specific concerns with the definition are addressed, and it is then explained why an account of communication predicated on information transfer is necessarily derivative upon such an approach. Other alternatives and some variants of the adaptationist definition are also briefly discussed.

The defining problem of animal signalling theory is how reliable communication systems remain stable. The problem comes into sharp focus when signals take an arbitrary form, as human words do. Many researchers, particularly those in evolutionary linguistics, assume that the handicap principle is the only recognised solution to this paradox, and hence conclude that the process that underpins reliability in humans must be exceptional. However, there are other examples of cheap yet reliable signals in nature, and corresponding processes that may explain such examples. This paper reviews these alternatives and concludes that by far the most likely explanation of the stability of human communication is our ability to assess individual reputation: we hold the threat of social exclusion against those who signal unreliably and hence keep their utterances reliable.

Many theories of language evolution assume a selection pressure for the communication of propositional content. However, if the content of such utterances is of value then information sharing is altruistic, in that it provides a benefit to others at possible expense to oneself. Close consideration of cross-disciplinary evidence suggests that speaking is in fact selfish, in that the speaker receives a direct payoff when successful communication takes place. This is congruent with the orthodox view of animal communication, and it is suggested that future research be conducted within this context.