Random utility maximisation is the preeminent behavioural theory used to model choices. An alternative paradigm, however, is random regret minimisation. While the majority of the literature examines the choices of individuals, this paper compares the choices of groups, as well individuals, in both the utility maximisation and regret minimisation frameworks and explores the influence household members have with respect to an automobile purchase decision within an interactive agency choice experiment. Regret minimisation is shown to be the preferred behavioural mechanism for groups and individuals within groups who shoulder a high degree of responsibility for the choice of the group.