Humans group speech sounds into categories. The processes by which we do so are a topic up for debate. My research along these lines has led me to embrace dual-system models of phonetic category learning, where listeners first attempt to use abstract, rule-based decision-making processes to categorize sounds, then, if necessary, fall back on the memorization of stimulus-to-category mappings. We began testing these theories using a typical English-speaking undergraduate population, learning categories of German sounds. In this presentation, I present data obtained, and experiments proposed, in populations different from these: in native German speakers in Tübingen, in kids who stutter in Michigan, and, hopefully soon, in a museum environment in Ohio. These results, we believe, continue to support the adaptation of dual-system models of category learning to phonetic learning tasks.