Shared cross-modal associations and the emergence of the lexicon

This thesis centres around a sensory theory of protolanguage emergence, or STP. The STP proposes that shared biases to make associations between sensory modalities provided the basis for the emergence of a shared protolinguistic lexicon. Crucially, this lexicon would have been grounded in our perceptual systems, and thus fundamentally non-arbitrary. The foundation of such a lexicon lies in shared cross-modal associations: biases shared among language users to map properties in one modality (e.g., visual size) onto another (e.g., vowel sounds). While there is broad evidence that we make associations between a variety of modalities (Spence, 2011), this thesis focuses specifically on associations involving linguistic sound, arguing that these associations would have been most important in language emergence. Early linguistic utterances, by virtue of their grounding in shared cross-modal associations, could be formed and understood with high mutual intelligibility. The first chapter of the thesis will outline this theory in detail, addressing the nature of the proposed protolanguage system, arguing for the utility of non-arbitrariness at the point of language emergence, and proposing evidence for the likely transition form a non-arbitrary protolanguage to the predominantly arbitrary language systems we observe today. The remainder of the thesis will focus on providing empirical evidence to support this theory in two ways: (i) presenting experimental data showing evidence of shared associations between linguistic sound and other modalities, and (ii) providing evidence that such associations are evident cross-linguistically, despite the predominantly arbitrary nature of modern languages. Chapter two will examine well-documented associations between vowel quality and physical size (e.g., /i/ is small, and /a/ is large; Sapir, 1929). This chapter presents a new experimental approach which fails to find robust associations between vowel quality and size absent the use of a forced choice paradigm. Chapter three turns to associations between linguistic sound and shape angularity, taking a critical perspective on the classic takete/maluma experiment (Kohler, 1929). New empirical evidence shows that the acquisition of visual word forms plays a highly influential role in mediating associations between linguistic sound and angularity, but that associations between linguistic sound and visual form also play a minor role in auditory tasks. Chapter four will examine a relatively unexplored modality: taste. A simple survey which asks participants to choose non-words to match representative tastes shows that certain linguistic sounds are preferred for certain food items. In a more detailed study, we use a more direct perceptual matching task with actual tastants and synthesises speech sounds, further showing that people make robust shared associations between linguistic sound and taste. Chapter five returns to the visual modality, considering previously unexmained associations between linguistic sound and motion, specifically the feature of speed. This study demonstrates that people do make robust associations between the two modalities, particularly for vowel quality. Chapter six will aim to take a different empirical approach, considering non-arbitrariness in natural language. Motivated by the experimental data from the previous chapters, we turn to corpus analyses to assess the presence of non-arbitrariness in natural language which concurs with behavioural data showing linguistic cross-modal associations. First, a corpus analysis of taste synonyms in English shows small but significant correlations between form and meaning. With the goal of addressing the universality of specific sound-meaning associations, we examine cross-linguistic corpora of taste and motion terms, showing that particular phonological features tend to connect to certain tastes and types of motion across genetically and geographically distinct languages. Lastly, the thesis will conclude by considering the STP in light of the empirical evidence presented, and suggesting possible future empirical directions to explore the theory more broadly.