The attitude-behavior relationship is of great import to many areas of psychology. Indeed, psychologists across disciplines have published thousands of articles on the topic. The majority of this research implies the attitude-behavior relationship is linear. However, observations from 4,101 Mechanical Turkers and 321,876 online reviews demonstrate that this relationship is systematically nonlinear. Across diverse topics, measures, and contexts, as attitudes move from extremely negative to extremely positive, the corresponding shift in behavior tends to be relatively flat at first (as attitude move from extremely to moderately negative), to steepen when attitudes cross neutral and shift from negative to positive, and to taper off again as attitudes move from moderately to extremely positive. This result can be explained based on research on categorical perception. The present research suggests a fundamental pivot in how researchers construe, study, and assess the attitude-behavior relationship.