Language Evolution and Computation Bibliography

(In Linguistic Evolution through Language Acquisition: Formal and Computational Models, edited by Ted Briscoe, Cambridge University Press. pp.301-344. Note: This HTML version may differ slightly from the printed version; the printed version is the `authorized' version. See a ...

Of the known animal communication systems, human languages appear to be unique in their use of recursively characterizable structural relations among sequences of sounds or gestures and the meanings those sequences can be used to express.

The patterns of structural relations that recursion makes possible can serve a range of communicative functions, tremendously extending the expressive resources of the system. Certain structural relations may be used to express specific meanings, or to modify, or extend, or restrict the meanings conveyed by words and other simple constituents.

Despite the unbounded complexity it makes possible, a recursive communicative system can be learned relatively easily because the constituents of a complex construction may themselves be simpler instances of that same kind of construction, and the properties of complex constructions are often predictable from simpler counterparts.

The research described in this paper is an investigation of how recursive communication systems can come to be. In particular, the investigation explores the possibility that such a system could emerge among the members of a population as the result of a process I characterize as ``negotiation,'' because each individual both contributes to, and conforms with, the system as it develops. The members of the population are assumed to possess general cognitive capacities sufficient for communicative behavior, and for learning to modify their behavior based on observations of others. However they are given no external guidance about how their communication system is to work, and their internal cognitive mechanisms impose few specific constraints.

A specific model of the ...

While most work on the evolution of language has been centered on the evolution of syntax, my focus in this paper is instead on more basic features that separate human communication from the systems of communication used by other animals. In particular, I argue that human language is the only existing system of learned arbitrary reference. While innate communication systems are, by definition, directly transmitted genetically, the transmission of a learned systems must be indirect. Learners must acquire the system by being exposed its the use in the community. Although it is reasonable that a learner has access to the utterances that are produced, it is less clear how accessible the meaning is that the utterance is intended to convey. This particularly problematic if the system of communication is symbolic -- where form and meaning are linked in a purely conventional way. Given this, I propose that the ability to transmit a learned symbolic system of communication from one generation to the next represents a key milestone in the evolution of language.

Human language is a unique natural communication system for two rea- sons. Firstly, the mapping from meanings to signals in language has structural properties that are not found in any other animal's communi- cation systems. In particular, syntax gives us the ability to produce an in nite range of expressions through the dual tools of compositionality and recursion. Compositionality is defined here as the property whereby an expression's meaning is a function of the meanings of parts of that expression and the way they are put together. Recursion is a property of languages with finite lexica and rule-sets in which some constituent of an expression can contain a constituent of the same category. Together with recursion, compositionality is the reason that this in finite set of expressions can be used to express different meanings.

Secondly, at least some of the content of this mapping is learned by children through observation of others' use of language. This seems not to be true of most, maybe all, of animal communication (see review in Oliphant, this volume). In this chapter I formally investigate the interaction of these two unique properties of human language: the way it is learned and its syntactic structure.