Abstract: Although there has been a proliferation of research and policy work into how nudges shape people’s behaviour, most studies stop far short of welfare analysis. In the current work, we critically reflect on recent efforts to proxy the welfare impact of nudges using willingness to pay and subjective wellbeing reports and explore an alternative unobtrusive approach: automatic facial expression coding. In an exploratory lab study, we use facial expression coding to assess the short-run emotional impacts of being presented with calorie information about a popcorn snack in the context of a stylized ‘Cinema experience’. The results of the study indicate that calorie information has heterogeneous impacts on people’s likelihood of choosing the snack and on the emotions they experience during the moment of choice which varies based on their level of health consciousness. The information does not, however, affect the emotions people go on to experience while viewing movie clips, suggesting that the emotional effects of the information are short-lived. We conclude by emphasising the potential of automatic facial expression coding to provide new insights into the short-run welfare effects of nudges and calling for further research into this promising technique.