Fairness is one of the most powerful social norms guiding how we interact with others in society. Yet much of our knowledge about fairness comes from controlled laboratory experiments with university students, settings that differ substantially from the diverse and socially complex environments where most everyday decisions occur. This gap motivated us to take a classic laboratory paradigm used to study fairness, the Ultimatum Game [1,2], into a completely different space: a museum open to the general public.
Our study grew from a simple idea: What happens if we placed a well-established psychological task about fairness into a space where everyday people make spontaneous decisions, free from the expectations of an experimental laboratory? We specifically wanted to know: Would previous research findings replicate in this more natural environment? And, could such a setting reveal any new aspects about social norms hidden by traditional experimental constraints? Over 13 months, and across more than 18,600 decisions received from volunteer members of the public, we found that the answer to both questions was: yes!
Building a laboratory inside a public museum
With the dual goals of research and outreach, we collaborated with the Donders Citylab, an initiative at the Donders Institute for Brain, Cognition and Behaviour at Radboud University that aims to foster curiosity among the general public about scientific insights into the human brain and behaviour, and to create opportunities for the public and researchers to learn from one another.
The project took place in muZIEum, an educational museum dedicated to raising awareness about visual impairments in Nijmegen, the Netherlands. To bring science closer to society, we installed three touchscreen kiosks in the busy waiting hall of the museum, with promotional material encouraging visitors to participate in our brief decision-making task. In this way, the boundary between “participant” and “visitor” merged. People who may never typically enter a university lab became research contributors while engaging with questions about behaviour and decision-making.
Importantly, there was no experimenter nearby, no monetary incentives, and no quiet cubicles. People encountered the task while waiting for their museum tour to begin, in the midst of conversations, with children in tow, or during an afternoon outing with schoolmates, colleagues, friends or family.
This environment created exactly what we sought: a setting where decisions would be made authentically, quickly, and without the “experimenter” mindset often associated with laboratory participation. Rather than eliminating real-world noise, we decided to embrace it as a meaningful part of understanding behaviour as it naturally unfolds. The challenge was thus to design a task intuitive enough to be completed in under five minutes by visitors ranging from school-aged children to retirees, yet rigorous enough to draw meaningful behavioural insights.
The core of our task was the Ultimatum Game, a foundational tool in fairness research [1,2]. It works as follows: One person receives a sum of money and proposes how to divide it between themselves and another person. The responder can accept (both receive the proposed amounts) or reject (both receive nothing). As rejection is costly, choosing to reject an unfair offer is widely interpreted as evidence of inequality aversion [1,2].
In our version, visitors played the role of responder and received four offers (two generous and two selfish) from anonymous game partners. Before deciding, they had the option to view up to five examples of that partner’s past offers to others. Whether people chose to view this, and how they used it, became central to the study.
Replicating classic fairness effects in an everyday setting
Our first question was whether findings from decades of laboratory research would hold in this more natural context. Our results indicate that they do.
Generous offers were accepted at over 92%, while selfish offers were accepted at only 34%, closely mirroring incentivised laboratory studies [2]. This suggests that core psychological mechanisms underlying fairness decisions persist outside controlled environments.
Fairness norms thus appear strong and detectable even in public, unsupervised settings. However, the museum environment also allowed us to move beyond replication.
The surprising importance of information sampling
An important discovery was that the overwhelming majority of participants chose to view information about their game partners’ past behaviour. Across all four partners, 79–89% of participants opened at least one box revealing historical offers.
Why does this matter? The past behaviour of a proposer is theoretically unnecessary for deciding in the Ultimatum Game. From a rational-choice perspective, participants need only consider the split in the current trial. Yet people wanted to know how the proposer had treated others before and indeed prior research shows that expectations strongly shape responses to offers [3,4].
This past information made a difference. Participants who sampled were far more sensitive to violations of fairness norms. When a proposer who had previously behaved generously suddenly made a selfish offer, rejection rates increased sharply among those who had sampled. In contrast, when a consistently selfish proposer made another selfish offer, sampling had little effect, that is participants already expected unfairness. Simply put, unexpected selfishness can feel more hurtful than expected selfishness.
This asymmetry reveals a key psychological process: people use voluntarily acquired information to form expectations about social partners, and these expectations shape judgements about unfairness. Sampling did not just simply provide additional information, it changed how participants interpreted the very same offer.
Fairness in daily life: age, time, and the rhythms of decision-making
The richness of our dataset allowed us to examine behavioural patterns rarely observed in laboratory studies. Two stood out:
Age mattered. Older participants were more likely to accept offers overall, including unfair ones, aligning with research suggesting increasing prosociality across the lifespan [5].
Time of day influenced information-seeking. Sampling increased across the day, with higher rates in the afternoon than in the morning, while acceptance remained stable. These patterns are supported by emerging evidence on diurnal fluctuations in exploratory tendencies [6], and suggests that fairness norms are robust, but exploratory behaviour follows temporal rhythms, an aspect standard laboratory studies rarely capture.
Why this methodological approach matters
This study demonstrates the value of lab-in-the-field research and the potential of citizen-science approaches for psychological research.
Thousands of visitors engaged directly with our experiment and, through an educational debriefing, learned about fairness, decision-making, and social expectations. At the same time, by placing a behavioural task in a real community space, we gained access to a large and heterogeneous participant pool and observed natural variability in social curiosity and decision-making.
Crucial to this project was the coordinated efforts of all actors involved, including the muZIEum, which provided the public space necessary for this endeavour, offering not just a venue but a willingness to embed scientific research into the flow of their visitors' day.
Looking ahead
Overall, our research revealed that: fairness norms persist outside of laboratory conditions; people voluntarily seek social information even when unnecessary; expectations formed through sampling powerfully shape fairness evaluations; and demographic and temporal dynamics influence information-seeking.
Our findings raise several questions: How do expectations formed through sampling influence judgements in more complex interactions? What biological or motivational processes underlie the time-of-day patterns we observed? How might these insights inform policies in which fairness and transparency are central concerns?
By placing a classic experimental task in a community environment, we aimed not only to study fairness differently but also to demonstrate what becomes possible when psychological research moves into the spaces where social decisions naturally take place. We hope this work encourages further exploration of ecologically grounded designs in communities, highlighting the scientific value of meeting participants where they already are.
References
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Sanfey, A. G. (2009). Expectations and social decision-making. Mind & Society, 8, 93–107.
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Chang, L. J. & Sanfey, A. G. (2013). Great expectations: neural computations underlying social norms. SCAN, 8, 277–284.
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Matsumoto, Y. et al. (2016). Prosocial behavior increases with age across five economic games. PLoS ONE, 11, e0158671.
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Gullo, K. et al. (2019). Does time of day affect variety-seeking? Journal of Consumer Research, 46, 20–35.