The Acceptance and Commitment Therapy belongs to the "third wave" of behavioral therapies. The first wave focused primarily on behaviorism, emphasizing observable actions and the idea that behaviors could be changed through conditioning techniques. The second wave, known as Cognitive Behavioral Therapy (CBT), integrated cognitive processes and focused on how thoughts and beliefs affect behavior. The third wave, which includes ACT, expands on these by incorporating mindfulness, acceptance, and contextual factors, shifting from merely modifying thoughts and behaviors to enhancing psychological flexibility and acceptance of internal experiences.