Categorization is an important facet of speech communication. However, we do not yet have a complete understanding of how speech categories are learned in infancy or adulthood. At least part of the reason for this is that it is not feasible to entirely control and manipulate speech to observe the consequences of different patterns of experience. Converging methods of cross ‐ language observation, laboratory ‐ based training of speech and nonspeech categories, and animal models of learning can provide a means of balancing the competing demands of ecological validity and experimental control to reveal how auditory and cognitive constraints affect speech category learning. The present half ‐ chapter describes evidence from these approaches and explains how this evidence informs us about how general perceptual and cognitive constraints affect learning speech categories