Before bilingual children can say anything, they must learn to differentiate between the two languages that are spoken to them, and they must learn to make useful perceptual distinctions in each of them in order to grasp what is said to them. Conversational interaction and non-verbal communication, like pointing and gaze, help children in attending to and processing aspects of their “language input environment” (De Houwer, 2009, 2011), “exposure” in Carroll's terms. As Carroll indicates, children must build up their linguistic categories based on their intrinsically category-free “exposure”: they must process speech to acquire language. This reminds of Wijnen's (2000) concept of language intake, which is the “data base children employ to derive hypotheses on the structure of the target grammar” (p. 174), and which constitutes children's selection from what this paper will continue to call input, pace Carroll.