How do children learn to communicate, and what do they learn? Traditionally, most theories have taken an associative, compositional approach to these questions, supposing children acquire an inventory of form-meaning associations, and procedures for composing / decomposing them; into / from messages in production and comprehension. This paper presents an alternative account of human communication and its acquisition based on the systematic, discriminative approach embodied in psychological and computational models of learning, and formally described by communication theory. It describes how discriminative learning theory offers an alternative perspective on the way that systems of semantic cues are conditioned onto communicative codes, while information theory provides a very different view of the nature of the codes themselves. It shows how the distributional properties of languages satisfy the communicative requirements described in information theory, enabling language learners to align their expectations despite the vastly different levels of experience among language users, and to master communication systems far more abstract than linguistic intuitions traditionally assume. Topics reviewed include morphological development, the acquisition of verb argument structures, and the functions of linguistic systems that have proven to be stumbling blocks for compositional theories: grammatical gender and personal names.

The concept of duality of patterning (henceforth DP) has recently begun to undergo new scrutiny. In particular, the fact that Al-Sayyid Bedouin Sign Language (ABSL) does not appear to exhibit a layer of meaningless units (Sandler et al. 2011) casts doubt on the universality of DP as a defining feature of natural language. Why, then, do the vast majority of the world's languages exhibit DP? Two hypotheses have been suggested. The first is that DP is a necessary solution to the problem of conveying a large number of meanings; the second is that DP arises as a consequence of conventionalization. We tested these hypotheses in an experimental-semiotics study. Our results supported the hypothesis based on conventionalization but were inconclusive with regard to the hypothesis based on the number of meanings. At the same time, the task of measuring DP in an experimental-semiotics study presented interesting challenges, suggesting that the concept of DP may need some overhauling.