Communicative emergence and cultural evolution of word meanings
Silvey, Catriona Anne
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The question of how language evolved has received an increasing amount of attention in recent years. Compared to seemingly more complex phenomena such as syntax, word meanings are usually seen as relatively easy to explain. Mainstream accounts in psycholinguistics and evolutionary linguistics assume that word meanings correspond to stable concepts which are prior to language and derive straightforwardly from human perception of structure in the world. Taking a cognitive linguistic approach based on psycholinguistic evidence, I argue instead that word meanings are conventions, grounded, learned and used in the context of communication. The meaning of a word is the sum of its contexts of use, with particular features of these contexts made more or less salient by mechanisms of attentional learning and communicative inference. Evolutionarily, word meanings arise as an emergent product of humans’ adapted tendency to infer each other’s intentions using contextual cues. They are then shaped over cultural evolution by the need to be learnable and useful for communication. This thesis presents a series of experiments that test the effect of these pressures on the origins and development of word meanings. Experiment 1 investigates the origins of strong tendencies for words to specify features on particular dimensions (such as the shape bias). The results show that these tendencies arise via attentional learning effects amplified by iterated learning. Dimensions which are less salient in contexts of learning and use drop out of word meanings as they are passed down a chain of learners. Experiments 2, 3 and 4 investigate the structure of word meanings produced during either paired communication games or individual labelling of images by similarity. While communication alone leads to word meanings that are unstructured and poorly aligned within pairs, communication plus iterated learning leads to word meanings that increase in structure and alignment over generations. Finally, Experiment 5 investigates the interaction of event structure and developing conventions in shaping word meanings. The structure of events in an artificial world is shown to influence lexicalisation patterns in the languages conventionalised by communicating pairs. Event features that are less predictable across communicative contexts tend to be more strongly associated with the conventions in the language. Overall, the experiments show that rather than straightforwardly reflecting pre-linguistic conceptualisation, word meanings are also dynamically shaped by learning and communication. In addition, these processes are constrained by the conventions that already exist within a language. This illuminates the mixture of convergence and diversity we see in word meanings in natural languages, and gives insight into their evolutionary origins.