Since the beginnings of speech research, the issue of variability has been a central topic in the field. Until recently, solutions to this problem have focused mainly on resolving linguistic forms from variable acoustic realizations, with little systematic consideration of talker variability or social settings. However, acoustic-phonetic variability within and between talkers does not arise by chance - such variation is attributable to a variety of causes including talker physiology, dialect, affect, and social/situational factors. Studies of conversational interaction demonstrate the influence of situational factors on many aspects of spoken communication. In particular, interacting talkers converge and diverge in acoustic-phonetic form over the course of a single conversational setting. Although phonetic convergence likely reflects a close connection between speech perception and production, it is not an automatic consequence of priming mechanisms or a mirror neuron system. In studies of the neural activity associated with speech perception, it is increasingly clear that utterances are processed in separate dorsal and ventral cortical streams, one that is part of the self-regulation of spoken utterances, and another that is part of conceptual understanding. Links between perception and production appear to be part of the self-regulatory system that participates in speech production control monitoring, which makes this system a likely candidate for talker control of acoustic-phonetic variability. Whether talkers converge or diverge depends on multiple aspects of the social setting, which have a much greater influence on the form of phonetic expression than automatic links or mirror mechanisms.