 How much of the perceptual development we undergo as infants and young children is the result of learning? There are many difficulties distinguishing development from learning, conceptually (for some discussion, see Carey 2009, especially pp. 11–14). The issue of how to distinguish development from learning bears on the traditional philosophical debate between nativists and empiricists (see Markie 2015, for a summary of that debate). In the perceptual learning literature, for instance, Kellman and Garrigan reject the view that all perceptual development is the result of learning, a view that they consider to be empiricist (2009: 57). Specifically, they think that data on infant perception collected in and around the 1980s provide evidence that at least some perceptual development is innate: