Primary Language Acquisition

Language is a species-specific trait that evolved in humans uniquely, and develops in the young universally. Infants acquire linguistic material at a fairly brisk pace, considering the seeming inadequacy of ambient models and the rarity of teaching or corrective feedback; and may, in certain circumstances, invent aspects of linguistic structure, as when pidgins are transformed into creoles, and deaf children streamline or embellish sign languages that have been awkwardly modeled by their non-natively signing parents. In some societies, parents attempt to facilitate language learning, but this practice does not occur universally, and it is unusual, in any culture, for caregivers to do much that is specifically tutorial---they do not, and probably cannot, teach grammar, nor do parents instruct their offspring in the principles of pragmatics or verbal performance. Collectively, these observations imply the operation of experience-expectant mechanisms that require perceptual access to talking people but place few additional demands on the infant’s social environment. In contrast, wild-living apes have no system of communication that approaches the complexity, flexibility, or utility of human language, and they give little indication of vocal or gestural learning. Where attempts have been made to teach signed or spoken languages to captive animals, comprehension has been demonstrated in several animals experimentally, but the instructed material has generally not been used naturally in social circumstances. The acquisition of language appears to depend on many things, and isolation of the most important factors has been difficult. Accounts of language development in humans are likely to benefit from identification of the linguistically relevant differences between humans and apes; and this requires, at a minimum, comparative studies of the social, neural, and cognitive mechanisms that differentiate the species, as well as differences manifesting at critical stages of life history.