An information processing system capable of estimating a driving conduct suited to a driver includes: a history obtainer that obtains a personal driving environment history of each of a plurality of drivers, each of the personal driving environment histories indicating one or more vehicle behaviors selected by the driver, and a driving environment associated with each of the one or more behaviors, the driving environment being a driving environment of the vehicle at a point in time of selection of the behavior it is associated with; and a modeler that models, from a driving environment history including the personal driving environment histories of the plurality of drivers, the personal driving environment history of at least one of the plurality of drivers, to build a driver model indicating a relationship between a behavior and a driving environment for the vehicle of the at least one of the plurality of drivers.