The idea that language has a constitutive involvement in human cognition is currently enjoying a resurgence in popularity. One group of enthusiasts for this idea consists of philosophers who have addressed the capacity of symbols in natural language to structure our cognitive environments (Clark, 1998, 2006; Dennett, 1997), and thus “reshape the computational spaces” (Clark, 1998, p. 174) that must be negotiated in problem solving. Another group includes developmental psychologists who, influenced by the writings of such figures as Mead (1934), Luria (1961), and Vygotsky (1930–1935/1978, 1934/1987), have focused on the ontogenetic linkages between language and thought (e.g., Berk, 1992; Tomasello, Kruger, & Ratner, 1993; Wertsch, 1991). Vygotsky (1930–1935/1978, 1934/1987) argued that words constitute a special category of “psychological tools” which fundamentally transform our biological brain processes to create a new class of mediated higher mental functions. Yet despite a renewed interest in such cognitive conceptions of language (e.g., Carruthers, 2002), the effects of linguistic enculturation on individual brain functioning remain mysterious. We may be agreed about the potential of words in natural language to function as tools for cognition, but there has thus far been little progress toward understanding which properties of language might enable words to fulfill this function, and in providing cognitive models of the interfunctional (Vygotsky, 1934/1987) relations between language and thought.
In this chapter, I focus on one implication of a broadly Vygotskian cognitive conception of language: namely, that the language that “gets into the head” to transform our prelinguistic thought processes preserves one important feature of external language.