Blackwell Publishing LtdOxford, UKAPPSpplied Psychology0269-994X © Int rnational Association for Applied Psychology, 2008XXXriginal Arti leMODELING HE LTH CHANGE BEHAVIORSCHWARZER Response Some Burning Issues in Research on Health Behavior Change

This response to five excellent commentaries is intended to clarify some issues in research on health behavior change that appear to be ambiguous or con-troversial, such as the debate about stage models versus continuum models or the search for moderators and mediators. The assumption of stages can be useful, but the quest for truly existing stages is considered fruitless because stage is a scientific construct, not nature. The Health Action Process Approach (HAPA) is designed as an implicit or explicit stage model, based on the distinction between a motivational and a volitional phase. As a template for targeted interventions, it suggests grouping individuals into preintenders, intenders, and actors. Due to indistinct boundaries between stages and to unstable social-cognitive constructs, the validity of stage assessment becomes the foremost problem. However, if stage-tailored interventions turn out to be superior to nontailored interventions, then the choice of the corresponding stage model is justified. When analysing the mechanisms of health behavior change or when predicting behaviors, the HAPA is also in line with nonstag