If children observe conventionality, they should take the adult language – the input they hear addressed to them – as the target to aim for. If they observe contrast, they should assume that differences in form signal differences in meaning. I begin by looking at the earliest evidence for conventionality and contrast, and then turn to specific predictions these principles make about lexical acquisition.

Conventionality

What evidence is there that children observe conventionality? First, they target adult words from the start. They store in memory word-forms based on what they hear from adults. They must do this for two reasons. First, children who have not stored in memory something close to the adult sequence cat, for example, would have no basis for recognizing it and responding systematically upon hearing it in such adult utterances as Look at the cat, Here's a cat, Find the cat, Get your cat, or Where's the cat? In order to map any meaning onto a word form, children must store both the form and its possible meaning. And for them to treat any sequence of sounds (potential word-forms) systematically, they need to have stored that sequence in memory in a shape close enough to the adult version to allow for recognition on subsequent occasions. As they are exposed to more of the input language, they must add to their repertoires of stored forms (plus tentative meanings) since they will rely on those in recognizing words and processing further utterances from the speakers around them.