Modern psychology has become a broad and fragmented collection of research areas, theoretical orientations, and professional organizations. The author, who believes integration within the discipline is critical, makes the case that its empirical and theoretical aspects can be unified under the umbrella of adaptation. The principles of learning, and the characteristics of memory and language—our adaptation to a challenging environment—are pertinent to all we do, and the sciences of learning and cognition are the subject areas most relevant to these proximate behavior–environment relationships. Because the adaptability of a behavior is often tied to its function, the author’s functional perspective serves as a helpful organizational tool for studying the otherwise disparate aspects of learning and cognition—thinking, memory, conceptual behavior, and language. New to this edition is an emphasis on applied behavior analysis, a rapidly growing and credentialed profession. Updated pedagogical features include opening chapter vignettes, interim summaries and review questions, improved graphics, and a full glossary of key terms.