Although the idea of a sense of self is widely used in psychology, the meaning of this phrase remains largely undefined. Self-recognition, self-esteem, and self-monitoring are important components of understanding one’s self, but without ways of understanding and measuring the development of this sense of self, it’s impossible for psychologists to conduct effective interventions and highly difficult for researchers to empirically investigate an individual’s sense of self and other. In The Self and Perspective-Taking, Steven Hayes, Ruth Baer, and other leading researchers explain how humans develop a sense of self through language and perspective development or perspective-taking . Perspective-taking refers to an individual’s ability to imagine circumstances other than their own, think objectively, and remain flexible and nonjudgmental when faced with others’ differences. The articles in this book explore behavioral, developmental, social, cognitive, and neurophysiological approaches to understanding the self and perspective-taking. Readers learn how to use relational frame theory (RFT) to grasp the development of self-understanding and discover how this knowledge can improve clinicians’ ability to improve self-understanding in others, especially in those with autism spectrum disorders and schizophrenia.