Human language is unique among the communication systems of the natural world. The vocabulary of human language is unique in being both culturally-transmitted and symbolic. In this paper I present an investigation into the factors involved in the evolution of such vocabulary systems. I investigate both the cultural evolution of vocabulary systems and the biological evolution of learning rules for vocabulary acquisition.

This thesis is the result of several years of research at the Research Centre of English

What shapes the meaning of a word? We can use a graphical metaphor to make intuitively clear that words can be shaped in three different ways. Consider the following three shapes: Figure 1: Three kinds of word meanings Some words are like the first shape in Figure 1, which has the very simple planar geometry of a circle: Figure 2: A classical word meaning 1 A circle can be defined by a simple equation like x 2 +y 2 = 1. This corresponds to the kind of word meaning that is determined by one simple definition. Bachelor, with its definition of ‘adult man who has not married yet’, is the classical example of such a monosemous word (Katz and Fodor 1963). It is of course well-known that word meanings are rarely like this. They are often polysemous, that is, clusters of closely related, more basic meanings. 1 In this sense, they can be compared to the second shape in Figure 1, a complex, irregular shape built up from simple planar figures: Figure 3: A cluster word meaning A well-known example of such a cluster word from the literature is over (Brugman 1981, Lakoff 1987). But there is a third way in which word meanings can be shaped, that has received much less attention in the literature and that is illustrated by the third shape in Figure 1. In this case the semantic outline of the word (the square) is determined by the meanings of other words that cut out parts of a regularly defined meaning and thereby create irregularity in the shape: Figure 4: A clipped word meaning 1 And even bachelor has more senses besides that of ‘adult man who has not married yet’. 2 The factor that shapes meaning in this case is not the polysemy of one single word, but interaction between different words. The idea that words and word meanings determine each other in patterns of competition and blocking is known from structuralism and Wortfeld

I hereby declare that this thesis has not been and will not be, submitted in whole or in part to another University for the award of any other degree.