How does Juicy Game Feedback Motivate? Testing Curiosity, Competence, and Effectance.

'Juicy' or immediate abundant action feedback is widely held to make video games enjoyable and intrinsically motivating. Yet we don’t know why it works: Which motives are mediating it? Which feedback features afford it? In a pre-registered (n=1,699) online experiment, we tested three motives mapping prior practitioner discourse---effectance, competence, and curiosity---and connected design features. Using a dedicated action RPG and a 2x2+control design, we varied feedback amplification, success-dependence, and variability and recorded self-reported effectance, competence, curiosity, and enjoyment as well as free-choice playtime. Structural equation models show curiosity as the strongest enjoyment and only playtime predictor and support theorised competence pathways. Success dependence enhanced all motives, while amplification unexpectedly reduced them, possibly because the tested condition unintentionally impeded players' sense of agency. Our study evidences uncertain success affording curiosity as an underappreciated moment-to-moment engagement driver, directly supports competence-related theory, and suggests that prior juicy game feel guidance on coherent feedback ties to legible action-outcome bindings and graded success as preconditions of positive 'low-level' user experience.