This dissertation applies current thinking in cognitive science to elements of the actor’s process of preparing and performing a role. Findings in the fields of neuroscience, psychology, and linguistics radically challenge the dualistic concepts that have dominated acting theory since the early twentieth century, and suggest more holistic models of the actor’s cognitive and expressive activities. Chapter 1 suggests how a vocabulary for nonverbal communication (nvc) drawn from social psychology can be used to analyze and describe actors’ communicative behavior. Chapter 2 examines the relationship of thought, language and gesture by considering Lakoff and Johnson’s (L & J) analysis of how conceptual thought is metaphorically shaped by the body’s experiences in the physical world. This assessment is combined with David McNeill’s theory that gestures are key ingredients in an “imagery-language dialectic” that fuels both speech and thought. Elements of both analyses are applied to Jacques Lecoq’s actor training exercises. Chapter 3 investigates the actor’s concepts of self and of character. This is supported by L & J’s analysis of the metaphorical construction of self and of different selves, a description of the connectionist view of mind, Merlin Donald’s proposition that mimesis is central to cognition, and Fauconnier and Turner’s theory of conceptual blending. Aspects of Michael Chekhov’s approach to character are considered in the light of theses findings and theories. Chapter 4 addresses the actor’s sense of identification with a character. I refer to work on proprioception, LeDoux’s exploration of the neural foundations of self, and Gallese and others’ work on “mirror mechanisms” in the brain that provide an experiential dimension to action and emotion understanding. I suggest that these findings validate the effectiveness of Stanislavski’s Method of Physical Actions. Chapter 5 describes the findings of Antonio Damasio, Joseph LeDoux and psychologist Paul Ekman on emotion, and applies them to exercises created by Stanislavski, Strasberg, Jerzy Grotowski, Jacques Lecoq, and Susana Bloch. The Conclusion proposes a model of the theatrical act, and suggests ways in which actor training can be remodeled in the light of the information described.