Unexpected events and prosocial behavior: the Batman effect | npj Mental Health Research
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Unexpected events and prosocial behavior: the Batman effect
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Human behaviour<br>Psychology
An Author Correction to this article was published on 17 June 2026
This article has been updated
Abstract<br>Prosocial behavior, the act of helping others, is essential to social life, yet spontaneous environmental triggers for such behavior remain underexplored. This study tested whether an unexpected event, such as the presence of a person dressed as Batman, could increase prosocial behavior by disrupting routine and enhancing attention to the present moment. We conducted a quasi-experimental field study on the Milan metro, observing 138 rides. In the control condition, a female experimenter, appearing pregnant, boarded the train with an observer. In the experimental condition, an additional experimenter dressed as Batman entered from another door. Passengers were significantly more likely to offer their seat when Batman was present (67.21% vs. 37.66%, OR = 3.393, p<br>Similar content being viewed by others
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Introduction<br>Prosocial behavior, voluntary actions that aim to benefit others, has profound implications for societal functioning and individual well-being1. These behaviors can stem from a variety of motivations, ranging from empathy-driven altruism to adherence to social norms or even egoistic goals like guilt reduction2. Although much of the literature has focused on internal motivations for prosociality, it is well established that contextual factors also matter. For instance, bystander research has demonstrated that situational features can substantially shape helping behavior3,4. Likewise, cues associated with romantic love have been shown to promote prosocial responses5. Building on such findings, more recent studies have examined how specific environmental triggers may directly encourage prosocial actions6,7,8. In particular, the focus of this study is on events that break the monotony of daily life, such as unexpected and novel occurrences, which may serve as catalysts for prosocial behaviors by fostering mindfulness and heightened awareness of the present moment. Novel and unexpected events can, in fact, trigger cognitive appraisal of one’s surroundings, as well as behavioral intentions9.<br>Mindfulness, typically cultivated through deliberate practices, is characterized by non-judgmental attention to the present moment. However, certain situational triggers, such as unexpected events, may similarly engage mindful awareness, directing attention away from habitual, automatic responses. Previous studies suggest that this attentional shift can enhance individuals’ sensitivity to the needs of others, potentially increasing prosocial behaviors.<br>This study investigates the hypothesis that unexpected events, such as the presence of a person in a superhero costume on public transportation or an unusual interruption in a classroom setting, can promote prosocial behavior. Drawing on theories of mindfulness and behavioral disruption, we propose that such events momentarily disrupt automatic patterns of attention and behavior, increasing individuals’ awareness of their surroundings and the needs of others. We aim to assess whether these disruptions can foster prosocial behaviors in an ecological environment, such as offering a seat to a pregnant woman on public transport. By exploring this intersection of mindfulness, novelty, and prosocial behavior, our findings could inform strategies to promote altruistic behaviors in daily life, from public art installations to innovative social campaigns. Based on these considerations, we hypothesized that the presence of an unexpected event (a person dressed as Batman) would increase the likelihood that passengers offer their seat to a pregnant woman, compared to a control condition without Batman.
Methods<br>Design and setting<br>The study was conducted in the Milan underground metro system, using a quasi-experimental design with two conditions. In the control condition, a female experimenter, pretending to be pregnant with a prosthetic belly, boarded the metro alongside a non-interacting observer (see Fig. 1). The experimental...