Exploring encouragement, treatment and spillover effects using principal stratification, with application to a field experiment on teens' museum attendance

This paper revisits results from a field experiment conducted in Florence, Italy to study the effects of incentives offered to high school teens to motivate them to visit art museums and to identify best practices to transform this behavior into a long run cultural consumption. Students belonging to a first group of classes receive a flier with basic information and opening hours of a main museum in Florence, Palazzo Vecchio. Students in a second group of classes receive the flyer and a short presentation conducted by an art expert. Students in a third group of classes, in addition to the flyer and the presentation, receive also a nonfinancial reward in the form of extra-credit points towards their school grade. Taking a Principal Stratification approach, we explore the causal pathways that may lead students to increase their future museum attendance. Within the strata defined by compliance to the three forms of encouragement, we estimate associative and dissociative principal causal effects, that is, effects of the encouragement on the primary outcome, long run cultural consumption, that are associative or dissociative with respect to the effects of the encouragements on the Palazzo Vecchio visit. This analysis allows to interpret these effects as ascribable either to the encouragements, or to the museum visits, or to classroom spillovers. To face identification issues, estimation is performed with Bayesian inferential methods using hierarchical models to account for clustering. The main findings of the analysis are as follows: what seems to matter the most is the motivational incentive (i.e., the presentation), rather than the induced experience, i.e., the Palazzo Vecchio visit.