Political reforms can be understood as the reconfiguration of formal institutions. The rational choice of formal institutions is the core topic of the New Institutional Economics research program. While bounded rationality is a core assumption of the New Institutional Economics and the reason for suboptimal behavior there, additional reference is made to the individual aspiration to intrapersonal consistency and interpersonal conformity here. These sources of a systematic deviation from the standard model of the homo oeconomicus result in systematic weaknesses of perception and deviations of behavior. This contribution connects shared mental models as informal institutions in the sense of North with well-established social psychological approaches and thereby leads to an integrative reflection of the insights in a stringent model framework.