Speech is extremely variable along many different dimensions. One source of variability listeners often encounter is accented speech, in which phonological units can systematically differ from the listener's native categories. This dissertation presents five experiments testing how listeners adapt to accent-based phonological variability, comparing the results within the framework of three competing hypotheses of phonological adaptation. Experiments 1A and 1B demonstrate that listeners store salient features of somewhat-familiar accents, Experiment 2B provides some evidence that listeners rapidly adapt to a novel accent, although they do not accept new lexical exemplars easily, and Experiment 3 shows that listeners treat accented shifts differently from mispronunciations, adapting to accented speech more quickly. Together, these experiments provided some evidence for all three hypotheses of phonological adaptation, suggesting that listeners may make use of a number of different strategies in order to successfully adapt to variability in the speech signal. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]