Gestures and Growth Points in Language Disorders

Gestures shed light on thinking-for-(and while)-speaking. They do this because they are components of speaking, not accompaniments but actually integral parts of it. Much evidence supports this idea, but its full implications have not always been recognized. For comparison, cf. modular-style modeling in de Ruiter (2000) and Kita & Özyürek (2005), based on the theory of speech production in Levelt (1989). Modular theory and its spinoffs are incompatible, we have argued, with the integration of gesture into speaking (McNeill, 2000; McNeill & Duncan, 2000). They require a fundamental separation of speech and gesture; the ‘modules’ exchange signals but cannot combine into a unit. The growth point (GP) hypothesis, which we describe here, is designed in contrast to explicate this integral linkage. In a GP, speaking and gesture are never separated, and do not occupy different brain processes that must in turn then be linked (cf. the brain model section, below). A key insight is that speech on the one hand and gesture (or, more broadly speaking, global-imagistic thinking), on the other, when combined into a GP, bring together semiotically opposite modes of cognition at the same moment. This opposition, and the processes that speakers undergo to resolve it, propels thought and speech forward; semiotic contrasts are a key component on a dynamic dimension of language. It is in this mechanism that we seek insights into language disorders. We explore four situations—disfluent (agrammatic) aphasia, Down’s syndrome, Williams syndrome, and autism. Each can be seen to stem from a breakdown, interruption or inaccessibility of a different part of the GP, and from a disturbance of the dynamic dimension in general. Considered together, they manifest—by interruption—aspects of the processes of thinking-for/while-speaking itself. We have not attempted to review gesture study, the growth point, the psycholinguistics of speech production, or language disorders, but do spell out some implications of a new paradigm in which language and cognition are embodied (cf., Johnson, 1987) and dynamic, and show how a theory within this paradigm, the growth point, leads to new insights into four language disorders.