A critical determinant of message interactivity is the presence of contingency, that is, the messages we receive are contingent upon the messages we send, leading to a threaded loop of interdependent messages. While this "conversational ideal" is easily achieved in face-to-face and computer-mediated communications (CMC), imbuing contingency in human-computer interaction (HCI) is a challenge. We propose two interface features—interaction history and synchronous chat—for increasing perceptions of contingency, and therefore user engagement. We test it with a five-condition, between-participants experiment (N = 110) on a movie search site. Data suggest that interaction history can indeed heighten perceptions of contingency and dialogue, but is perceived as less interactive than chatting. However, the chat function does not appreciably increase perceived contingency or user engagement, both of which are shown to mediate the effects of message interactivity on attitudes toward the site. Theoretical implications for interactivity research and practical implications for interaction design are discussed.