The practice of yoga, hypnosis, and the use of psychedelic drugs to alter psychological and physiological states is not unknown to the study of psychology. They have been called "soft" studies and labeled unimportant. This is mostly because they are difficult to study and understand, often focusing on unobservable internal states such as altered states of consciousness, Samadhi, or hypnotic states. This book, in its approach to thinking about this topic and method for analysis, focuses only on phenomena that can be observed, such as behavioral changes.

By centering on only those...