Are freely chosen actions generated by stimulus codes or effect codes?

A long-standing debate revolves around which mental codes allow humans to control behavior. The internal stimulus model (going back to Rudolf Hermann Lotze) proposes that behavior is controlled by codes of stimuli that had previously preceded corresponding motor activities. The internal effect model (going back to Emil Harleß) proposes that behavior is controlled by codes of perceptual effects that had previously resulted from corresponding motor activities. Here, we present a test of these two control models. We observed evidence for both models with stronger evidence for the internal stimulus model. We suggest that the proposed experimental setup might be a useful tool to study the relative strengths of stimulus control and effect control of behavior in various contexts.