By affording interactive communication and natural, human-like conversations, can media tools affect the way we engage with content in human-machine interactions and influence our attitudes toward that content? A between-subjects experiment (N = 172) examined the effects of two communication variables: (a) message-interactivity and (b) conversational tone, in an online health information (Q&A) tool. Findings suggest that informal conversational tone lowers perceptions of relative susceptibility to health risks. Perceived contingency positively mediates the influence of message interactivity on individuals' health attitudes and behavioral intentions whereas perceived interactivity negatively mediates the relationships between these variables. These contrasting mediation effects are further explored via a phantom model analysis that tests two theoretically distinct paths, with implications for both theory and practice.Keywords: Interactivity, Contingency, Turn-Taking, E-Health, Online Health, Interactive Health Technologies. doi:10.1111/hcre.12094 A poll by the National Public Radio, the Robert Wood Johnson Foundation, and the Harvard School of Public Health (2012) revealed that a majority of individuals (61%) are dissatisfied with the amount of time that doctors spend talking with their patients. In order to address it, many individuals are turning to online health resources (Fox & Jones, 2009;Rice, 2006), such as interactive quizzes and risk assessment tools. However, very little is known about their impact. This study explores how interactive tools affect users' understanding of health risk information, attitudes, and behavioral intentions.Corresponding author: Saraswathi Bellur; e-mail: saras.bellur@uconn.edu This article was accepted for publication under the editorship of Dr. John Courtright.[Correction added on 9/20/2016, after initial online publication: "Acknowledgments section added and typo on page 17 fixed (asystematic to a systematic)."] Knowing how online health tools are designed could help us assess their impact. A common characteristic is their interactive nature, that is, they provide information based on each user's unique input into the system. Conceptually, this aspect of interactivity is known as the contingency principle: the capacity of a system (or an interaction partner) to maintain highly interdependent message exchanges (Burgoon, Bonito, Bengtsson, Ramirez, et al., 2000;Rafaeli, 1988;Rafaeli & Sudweeks, 1997;Sundar, Kalyanaraman, & Brown, 2003).However, while contingent exchange of information constitutes one facet of interactive media, it does not capture another important aspect-namely, the tone of the communication. As Brennan (1998) pointed out, individuals are preoccupied not only with what they tell each other but also how they say it. If a communication scenario was to involve strictly task-oriented exchanges (e.g., ATM machine dispensing cash), the display of affiliation behaviors, such as a friendly conversational tone, may not be important. However, as studies in patient...