Individuals and collectives frequently apply specific modes of reasoning whn explaining why they engage in certain practices, and not in others. Often such explanations must be regarded as ex-post rationalisations since much human behaviour is routine-like, and influenced by social-psychological processes of which people are not immediately aware. Nevertheless, policy makers and other change agents frequently try to influence human reasoning and behaviour through the communication of knowledge claims and arguments that derive from science or other sources. This is increasingly complemented by the use of moral and/or emotional appeals. Many such efforts appear to fail. At the same time, we do witness cases in which confrontation with new perspectives, knowledge and appeals can indeed lead to a widening of the space in which people look for solutions and alterative courses of action. It is important therefore to improve our understanding of when and how knowledge encounters may affect human reasoning and behaviour. How are appeals and insights processed and mobilised by individual and collective actors to enlarge their space for manoeuvre? How do different bodies of knowledge and epistemic communities collide at social interfaces? In this area, metholodogical questions focus on the workings and value of different communicative strategies, varying from persuasive campaigns to forms of trans-disciplinary action research.