3Chapter 2 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. Consider modular-style modeling of the relationship between gesture and speech, for example, De Ruiter (2000) and Kita and Özyürek (2003), based on the theory of speech production in Levelt (1989). Modular theory and its spin-offs are incompatible, we have argued, with the facts of integration of gesture into speaking (McNeill, 2000; McNeill & Duncan, 2000). Such models 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 the integral linkage of gesture and speech in natural language production. 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, below). A key insight is that speech on the one hand and gesture (or, more broadly speaking, global-imagistic thinking), on the other, jointly forming 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 in the dynamic dimension of language. It is in this mechanism that we seek insights into language disorders. We explore four situationsdisuent (agrammatic) aphasia, Down syndrome (DS), Williams syndrome (WS), 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 of language in general. Considered together, they manifest-by interruption-aspects of the processes of thinking-for/while-speaking itself. In this chapter we do not attempt to review the eld of gesture studies, the psycholinguistics of speech production, or language disorders, but we do provide a brief exposition of the GP hypothesis and 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 GP theory, leads to new insights into four language disorders.