Thinking Through Language* PAUL BLOOM AND FRANK C. KEIL 1. Introduction What would it be like to have never learned English, but instead only to know Hopi, Mandarin Chinese, or American Sign Language? Would that change the way you think? Imagine entirely losing your language, as the result of stroke or trauma. You are aphasic, unable to speak or listen, read or write. What would your thoughts now be like? As the most extreme case, imagine having been raised without any language at all, as a wild child. What—if anything—would it be like to be such a person? Could you be smart; could you reminisce about the past, plan the future? There is a common sense set of answers to these questions, one that rep- resents the mainstream in many circles of cognitive science (see Pinker, 1994 for a lucid exposition). Under this view, the language you speak does not affect how you think. Rich, powerful and abstract cognition can take place within minds that, due to injury or deprivation, have no natural language. Even babies know about the kinds and individuals that occupy their world. They just don’t know their names. Before being exposed to words in a language such as English, all humans possess the concepts that these words correspond to, as part of what Jerry Fodor (1975) calls ‘mentalese’ or ‘a langu- age of thought’. Under this view, as Fodor puts it, all language learning is actually second language learning—when a child learns the vocabulary of English, all that happens is that the child learns the mappings from the English words onto the symbols of this prior language of thought. There is another perspective, however, one that is also rooted in common sense, and which is popular across many disciplines. Many linguists and anthro- pologists claim that the language one learns has a profound influence on how *This is the fourth in a series of Millennial pieces that have been specially commissioned by Mind & Language to appear in this volume and the next. Each contributor has been allowed choice as to topic and approach, being asked only to present a personal view of issues that he or she sees as being important in the present context of cognitive studies. Some of the article is a modified version of Bloom (2000, Ch. 10). Parts of this paper benefited from support provided by NIH Grant R01-HD23922 to Frank Keil. Address for correspondence: Department of Psychology, P.O. Box 208205, Yale University, New Haven, CT 06520, USA. Email: [email protected] or [email protected] Mind & Language, Vol. 16 No. 4 September 2001, pp. 351–367. Blackwell Publishers Ltd. 2001, 108 Cowley Road, Oxford, OX4 1JF, UK and 350 Main Street, Malden, MA 02148, USA. 352 P. Bloom and F.C. Keil one thinks. Many developmental psychologists have been struck by the correlation between language development and cognitive development—a12- month-old has few words and a limited mental life; a 24-month-old has many words and a much richer mental life—and see this as showing that language development has a profound influence on cognitive development. And many philosophers reject the idea that thought, or at least rich and abstract thought, can exist without language. Indeed, it is often claimed that the unique cogni- tive powers of our species are largely by-products of our evolved communicat- ive abilities (see Bloom, 1998 for review and discussion). From this perspective, speakers of English think differently from speakers of Hopi, and people who have no language will inevitably have an impaired mental life. There are many versions of the language-affects-thought claim. One version, most often associated with Whorf (1956) and Sapir (1921), is that differences between languages, such as between English and Hopi, lead to differences in thought. Another version, sometimes attributed to Vygotsky (1962), is that cognition is shaped by properties that all languages share. From this second perspective, the interesting contrast isn’t between speakers of English versus speakers of Hopi; it is between speakers of any language versus those people or animals who have no language at all.1 These two views are not independent. One can sensibly claim that there exist language-general effects without believing in linguistic-specific effects— universal features of language shape human thought, but differences are irrel- evant. For instance, if one were to hold the view that the acquisition of basic syntactic structure (phrases and sentences) has a profound effect on how people think about the world, this would be a language-general theory but not a language-specific theory—since all languages have this basic syntactic structure. On the other hand, it would be perverse to claim that differences between languages have an effect on thought, but to deny that there is also some more general effect of knowing a language as opposed to not knowing a language. Even putting aside the more subtle universal properties posited by linguists, nobody would doubt that all languages have words and that all languages have syntax. And it is words and syntax that are most often argued to have effects on thought. In sum, we see three tenable positions, each of which is very much in play in the cognitive science community. One can believe in language-general effects. One can believe in both language-general effects and language-specific effects. And, of course, one can believe that neither of these effects exists. A second sort of distinction between different theories of how language 1 There is also the view, defended by Bickerton (1995), that it is not exposure to a natural language such as English that gives rise to cognitive effects—it is the mere possession of a language faculty. This view merits discussion, but for reasons of space, we will restrict our- selves to the more standard proposal that exposure to a natural language is a catalyst to human thought. Blackwell Publishers Ltd. 2001 Thinking Through Language 353 affects thought concerns the aspect or aspects of language that are said to matter. The most obvious cut is between words and syntax. Some scholars argue that the specific words that a language has determines how our minds break reality into different chunks; others propose that our thoughts coalesce into larger complexes through the vehicle of syntax. But this contrast is oversimplified. Morphology lies at the interface between words and syntax, and can move from the level of the word to the level of the sentence, especially when polysynthetic languages are considered. Semantics principles of compo- sitionality, such as those involved in quantifier scope resolution, blend the boundaries between grammar and word meaning. And words themselves are a heterogeneous class—verbs, for instance, are sometimes argued to have a radically different role in influencing thought than nouns; closed class words, such as conjunctions and prepositions, are sometimes argued to have very dif- ferent cognitive effects than open class words, such as nouns and verbs. A third distinction concerns the assumed magnitude of the effect of language. Language can be seen as having mild effects on some aspects of cognition; mere icing on the mental cake. Alternatively, language can be seen as having such a massive effect that those who lack it have a profound and crippling deficit. Daniel Dennett (1996, p. 17) characterizes the strongest ver- sion of the proposal with characteristic panache: ‘Perhaps the kind of mind you get when you add language to it is so different from the kind of mind you can have without language that calling them both minds is a mistake.’ A fourth distinction concerns the types of effect that language is said to have. Here the proposals are quite varied. For instance, language has been said to affect our on-line perception of the world, to shape the categories we form, to enable us to perform logical inference and causal reasoning; to underlie social reasoning, and to structure our basic ontological commitments (about time, space, matter). We will discuss many of these specific claims in what follows. Our goal in this paper is not to provide a systematic geography of the different claims. Nor will we discuss all the major threads of theory and research; the literature is just too big to do so here.2 We will focus instead on more general methodological and theoretical questions: How can we make real progress on the debates over what, if anything, language does to thought? What evidence is most relevant? Which versions of the language-affects- thought claim are coherent, and which are likely to be true? 2 Largely absent from our discussion will be an analysis of three interesting and provocative claims about cognitive development—the proposals that words aid in the formation of sortal concepts (Xu, 1999; Xu and Carey, 1996), that words serve to link up the output of distinct modules (Carruthers, 1996; Mithen, 1996; Spelke and Tsivkin, 2001), and that syntax leads to the emerging understanding of the mental states of other people (e.g., deVilliers and deVilliers, in press; Tager-Flusberg & Sullivan, 2000). We hope to discuss these views else- where. Blackwell Publishers Ltd. 2001 354 P. Bloom and F.C. Keil Before getting to all this, however, we should point out that the issue here is not about whether language can have an effect on thought. Of course it can. (If it couldn’t, why would you be reading this?). Nobody doubts that language can inform, convince, persuade, soothe, dismay, encourage, and so on. This is what language is for. It is clear that much of the content of our minds exists because of information conveyed through the medium of langu- age.