James O. Prochaska is a prominent psychologist best known for developing the Transtheoretical Model of Behavior Change. This model outlines the stages individuals go through when changing a behavior, such as quitting smoking or adopting a healthier lifestyle. His work has significantly influenced health psychology and interventions aimed at promoting positive behavior changes. Prochaska's research emphasizes the importance of understanding an individual's readiness to change, which can vary widely. He has authored numerous publications and contributed to various health-related fields, making his theories widely applicable in areas like public health and addiction treatment.