This study investigates adults' ability to change their phonetic systems in perception and production, specifically upon exposure to a new dialect in adulthood. It further addresses the relative importance of binary biological sex and socially constructed gender in predicting an individual's sociolinguistic variation. Perception and production data was collected from lifelong residents of southern Indiana, lifelong residents of Chicago, and individuals raised in southern Indiana who moved to Chicago in adulthood (the Mobile group). The Mobile participants were shifting from their native Lower Midland or Upper South dialect and adopting the Northern Cities Shift (NCS) characteristic of Chicago. A gender identity test, the Extended Personality Attributes Questionnaire, was also administered to each participant. Results indicate that both perception and production are malleable in adulthood, but production may be more subject to change than perception. However, this relationship is not constant across individuals: some Mobile group members changed production more than perception, but others changed perception more, and still others had shifted the two equally or not at all. Analyses suggest that socially constructed gender and educational level may be reliable predictors of an individual's pattern in adopting a second dialect's phonetic system in adulthood. Interestingly, an individual's femininity level may be more important than her masculinity in determining behavior. This study has implications for the research areas of language change across the lifespan, gender and language, second dialect acquisition, second language acquisition, and American dialectology. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]