Traditional CBT encompasses various psychotherapeutic approaches based on the fundamental theory that a person's thinking is the fundamental factor influencing emotional and behavioral responses to life situations. CBT originated in the 1950s and 1960s and was popularized through the works of Albert Ellis' Rational-Emotive Behavior Therapy (REBT) and Aaron Beck's Cognitive Therapy (Robertson, 2010). Both models emphasized that cognitions, in the form of judgments, meanings, attributions, and hypotheses related to life events, are the primary factors that determine how individuals respond to environmental stimuli (Robertson, 2010). Today, CBT incorporates both cognitive and behavioral techniques. There are several derivations of CBT, but the different variations all share three assumptions for mechanisms of change. The first assumption is that cognitive activity influences behavior. The second assumption is that cognitive activity can be monitored or altered. The third assumption is that desired behavioral change can be influenced through cognitive change (Robertson, 2010). All variants of CBT share the theoretical perspective that hidden internal processes occur, including thinking or cognition, and that cognitive events can mediate behavior change. In therapy, the clinician and client take an active approach to addressing thinking, evaluating the validity and functionality of thoughts and formulating a more rational, logical, and realistic approach to interpreting one's reality (Robertson, 2010). Unlike traditional CBT, acceptance and commitment therapy (ACT) tends to de-emphasize direct strategies of cognitive and emotional change, and instead employs an ongoing cultivation of defusion and psychological acceptance (Herbert & Fo...... half of the article... ...d "look on the bright side" in difficult situations to ameliorate one's distress, or cultivate "positive attitudes" that can lead to better performance and more positive behaviors and on behavior are a fundamental focus that interventions are targeted at distorted, dysfunctional, and maladaptive cognitions. In ACT, an important feature is the decoupling of subjective experience from overt behavior (Hayes, 2004). they do not align with one's cognitions or affective states. Instead, ACT emphasizes changing the relationships between cognitions and behaviors, rather than changing the content of the cognitions themselves. Through acceptance and defusion strategies, individuals can gain psychological flexibility.