Referent properties and word order in emerging communication systems
Why do languages look the way they do? This question lies at the core of much of linguistics research, and answering it can shine a light on the relationship between individual cognitive preferences and linguistic structure. One area that has attracted particular attention is basic word order. Many mature languages exhibit a fixed or dominant ordering of subject (S), object (O), and the verb (V). However, evidence from restricted communication systems, such as emerging sign languages, shows that even before such conventions have been established, language producers show strong ordering preferences. It has been suggested that SOV is the natural ordering of entities in an event, and the default order used by all newly emerging languages. Over the past decade or so, a growing body of research has endeavoured to investigate this question using the silent gesture paradigm in which participants describe events using only their hands. This work has been instrumental in uncovering a range of factors that influence the way people convey information about events in the absence of linguistic conventions, challenging the view that there is a single natural order. In this thesis, I present a series of experimental studies, implementing new techniques for data collection and analysis, showing how properties of individual referents influence the word orders people use to convey information about simple transitive events. I start, in Chapter 2, with a detailed review of the silent gesture literature, highlighting the numerous accounts that have been offered to explain word order preferences. One theme common to many of these accounts is that there is a direct relationship between word order and the structural and semantic properties of events. In Chapter 3, I report a silent gesture experiment in which I investigate an additional, complementary factor, namely, the salience of entities in an event. In the data analysis, I develop a novel computational method for inferring word order preferences based on incomplete gesture strings. The results of this study suggest that the relationship between salience and word order is not necessarily linear. Rather, manipulating the salience of referents influences the perspective from which a producer frames an event, which in turn influences structural choices. The results, however, are inconclusive about whether these structural choices reflect a direct mapping from conceptual structure to word order. In Chapter 4, I investigate the role of another operational factor: biases specific to the gestural modality. I report three experiments in which participants conveyed information about events by selecting pictorial representations of event components. Although the findings from this study are inconclusive, they nevertheless highlight important questions about the effects of other task-specific factors such as the way elicitation stimuli are presented. In Chapter 5, I focus on the relationship between word order and one of the most fundamental determiners and drivers of linguistic structure - animacy. Using a series of artificial language learning experiments, I test two existing accounts that have been proposed to explain animacy-based word order variation. One emphasizes communicative pressures arising from the potential ambiguity of events involving two human referents; the other focuses on the salience of humans relative to inanimate objects. The results of this study offer tentative support for the salience-based hypothesis. Nevertheless, I suggest that further work is required to understand how language producers negotiate the communicative challenge of accurately conveying information about events where the role played by each of the noun referents is ambiguous. Echoing the conclusions from the previous two studies, I also highlight the need for more research to better understand the role played by other factors, such as modality and native language. Overall, the studies reported in this thesis demonstrate that word order in newly developing languages not only reflects structural and semantic properties of events, but is also influenced by properties of referents interacting in an event, for example, salience and humanness. While the overall findings are inconclusive about the precise nature of this relationship, they nevertheless add to a growing body of literature showing that structural choices in the absence of linguistic conventions do not conform to a single natural order, but are subject to the effects of a range of potentially interacting factors.