The challenge: Some properties of language can be learned without linguistic input

Usage-based accounts of language-learning ought to predict that, in the ab-sence of linguistic input, children will not communicate in language-like ways. But this prediction is not borne out by the data. Deaf children whose hearing losses prevent them from acquiring the spoken language that surrounds them, and whose hearing parents have not exposed them to a conventional sign lan-guage, invent gesture systems, called homesigns, that display many of the prop-erties found in natural language. Children thus have biases to structure their communication in language-like ways, biases that reflect their cognitive skills. But why do the deaf children recruit this particular set of cognitive skills, and not others, to their homesign systems? In other words, what determines the bi-ases children bring to language-learning? The answer is clearly not linguistic input. Usage-based theories of language acquisition hold that children acquire lan-guage by applying general learning skills to patterns in their linguistic input