Motivation has traditionally been conceptualized as something situated inside the person, which might explain certain behaviors and play a causal role in overt changes in behavior. This type of approach was assumed by the Transtheoretical Model of Change and Motivational Interviewing in the area of clinical and health psychology. In contrast, the behavioral concept of establishing operation is defined as a stimulus or environmental operation that momentarily alters the functions of other stimuli and the response probability, which allows us to study motivation without making inferences or assuming a cognitivist terminology. From this point of view, the study of motivation in therapy implies the analysis of the effect that certain verbalizations of the therapist have on the client's behavior. Moreover, we propose that the analysis of therapists' motivating verbalizations should focus on descriptions of the past, present and future consequences of the client's behavior.