Figure 2. .

Phonetic category learning vs. perceptual space learning. (a) Under standard phonetic category learning theories, infants identify categories early. As a result, perception becomes warped along phonetically relevant dimensions (Dimension 1) and discrimination decreases along phonetically irrelevant dimensions (Dimension 2). (b) An alternative theory is that learners’ perceptual space undergoes substantial changes before phonetic categories are learned. In this simplistic example, perceptual learning collapses the dimension of lower variance, decreasing discrimination along Dimension 2. As described later, we believe perceptual space learning actually involves more complex transformations.