An implicit assumption underlying previous interactivity studies is that every time people use a communication medium (e.g., website) or device (e.g., smartphone), they perceive its interactivity through analyzing it from scratch trait-by-trait. As psychologists have long shown, however, we quite often skip such an intensive analysis, and rely on our expectations or schematic knowledge to perceive/evaluate an object. This study is designed to develop a measure of individuals’ expectation of interactivity toward a medium, called expected interactivity (EI). After specifying three conceptual dimensions underlying EI – sensory, semantic, and behavioral dimensions – scales for capturing them are developed, refined, and validated through multiple studies. Implications for future interactivity research are discussed.