Two participants have to decide jointly, with the discussions preceding their choice being video/audiotaped. For two tasks, one with and one without strategic interaction, we refer to obvious reasoning styles as mental models. The videotaped discussions are analyzed according to which mental models are mentioned by one or both participants in the same pair and how decisive such arguments were. The mental models for the risky choice task are “analytic approach,” “commitment mode,” and “avoid chance,” and for the outside-option game “equality seeking,” “backward induction,” and “forward induction.” We classify each pair according to their mental constellation in both tasks and assess mental models in addition to collecting choice data. Altogether, this allows for better explanations, especially of heterogeneity in reasoning and deciding.