saw the rise of cognitive science, an interdisciplinary approach to studying the human mind. Cognitive science again considers the "mind" as a subject for investigation, using the tools of cognitive psychology, linguistics, computer science, philosophy, behaviorism, and neurobiology. This form of investigation has proposed that a wide understanding of the human mind is possible, and that such an understanding may be applied to other research domains, such as artificial intelligence. There are conceptual divisions of psychology in so-called "forces" or "waves," based on its schools and historical trends. This terminology is popularized among the psychologists to differentiate a growing humanism in therapeutic practice from the 1930s onwards, called the "third force," in response to the deterministic tendencies of Watson's behaviourism and Freud's psychoanalysis. Humanistic psychology has as important proponents Carl Rogers, Abraham Maslow, Gordon Allport, Erich Fromm, and Rollo May. Their humanistic concepts are also related to existential psychology, Viktor Frankl's logotherapy, positive psychology (which has Martin Seligman as one of the leading exponents), C. R. Cloninger's approach to well-being and character development, as well as to transpersonal psychology, incorporating such concepts as spirituality, self-transcendence, self-realization, self-actualization, and mindfulness. In cognitive behavioral psychotherapy, similar terms have also been incorporated, by which "first wave" is considered the initial behavioral therapy; a "second wave", Albert Ellis's cognitive one; and a "third wave", with the acceptance and commitment therapy, which emphasizes one's pursuit of values, methods of self-awareness, acceptance and psychological flexibility, instead of challenging negative thought schemes. A "fourth wave" would be the one that incorporates transpersonal concepts and positive flourishing, in a way criticized by some researchers for its heterogeneity and theoretical direction dependent on the therapist's view. A "fifth wave" has now been proposed by a group of researchers seeking to integrate earlier concepts into a unifying theory. Early psychological thought Many cultures throughout history have speculated on the nature of the mind, heart, soul, spirit, brain, etc. For instance, in Ancient Egypt, the Edwin Smith Papyrus contains an early description of the brain, and some speculations on its functions (described in a medical/surgical context) and the descriptions could be related to Imhotep who was the first Egyptian physician who anatomized and discovered the body of the human being. Though other medical documents of ancient times were full of incantations and applications meant to turn away disease-causing demons and other superstition, the Edwin Smith Papyrus gives remedies to almost 50