We examine why science is important to applied psychology, even if one’s motivation to be a psychologist is primarily practical. Helping others takes knowledge and skill, and often applied psychologists face situations that do not produce immediate or clear outcomes. In such situations experiential learning can only do so much, and science is needed to be effective long term. When the history of training models in applied psychology is reviewed from the inception of the field to the present day, it is clear that students of applied psychology need to learn how to do research that will inform practice, how to assimilate the research evidence as it emerges, and how to incorporate empiricism into practice itself. We argue that the kind of knowledge needed by practitioners requires a focus on the needs of those served by psychologists, a more personalized and process-based research approach, and a laser-like focus on issues of broad importance. A scientist-practitioner is a consumer of research, but is also able to identify, acquire, develop, and apply empirically supported treatments and assessments to those in need, and to think about their own work with an empirical mind set.

This chapter describes how the transtheoretical model of behavior change (TTM) provides a framework to guide the development of tailored behavior change interventions. The TTM includes four critical concepts: stages of change to delineate critical motivational and behavior change tasks; processes of change to identify a multidimensional set of mechanisms individuals use to accomplish stage tasks and make change happen; context of change to identify contextual resources and problems that promote or hinder personal change; and markers of change that are used to track important decisional and self-efficacy dimensions related to movement through the process of change. The TTM has been used to develop interventions for pre-action and action-oriented stage tasks and offers a unique perspective for understanding how behavior changes. TTM constructs have been used and evaluated in diverse clinical and cultural settings with both mental and physical health conditions. There is substantial support for the constructs and for tailoring interventions using these constructs across multiple studies. This chapter offers concrete strategies from diverse intervention approaches that can be used to address the varied motivation and behavior change tasks represented by the stages of change. Finally, implications for prevention, treatment, and training are discussed.