Applied behavior analysis is an evidence-based mental health approach that focuses on the principles of learning and applying what is learned to change client behavior. Written by leading experts in language and cognition, this is the first applied behavior analysis textbook to bring the study of language and verbal behavior into the 21st century with the latest research. Students and clinicians in the burgeoning field of applied behavior analysis will find the theoretical foundation they need to effectively serve the increasingly diverse clients seeking their services.