Published research

Human societies rely on rules to coordinate behaviour, sustain cooperation and maintain social order. Yet compliance can be fragile when rules are weakly enforced and individuals observe others violating them. Prior research shows that rule violations and other antisocial behaviours can spread through social influence, but less is known about how the severity of violations shapes these dynamics. In many real-world settings, rule-breaking occurs in degrees, from minor infractions to major violations, and individuals may not only imitate others but sometimes exceed the violations they observe. Here, we combine simulations and a behavioural experiment (n = 750) to study how the magnitude of observed rule violations shapes subsequent violations, and how this can generate escalation dynamics. Our simulations show that when individuals occasionally escalate beyond observed violations, even rare escalation can trigger a rapid shift from widespread compliance to collective rule-breaking. In our pre-registered experiment, observing major violations strongly increased rule-breaking, especially when committed by socially close others. Observing minor violations prompted many participants to follow suit and a minority to escalate beyond the violations they observed. Parameterizing the simulations with these behavioural responses shows that such escalators can disproportionately undermine collective compliance. These results highlight how asymmetric responses to rule violations and rare escalatory behaviour can transform small deviations into large-scale breakdowns of rule compliance.

Defaults are powerful: whereas wisely set defaults increase prosocial choices, poorly set defaults promote selfish decisions. In two preregistered studies (N_{Study 1} = 584, N_{Study 2} = 587), we test whether distracting environments, compared to distraction-free environments, make people rely more on selfish than prosocial defaults. Participants completed repeated binary dictator games in a 2 (selfish default vs. prosocial default) x 2 (distraction vs. no distraction) within-subjects design. Results from both studies and an internal meta-analysis provide no support for the hypothesis. Whereas participants accepted prosocial more than selfish defaults (in Study 1 and in an internal meta-analysis), the existence (vs. absence) of distraction did not affect default acceptance differentially for selfish versus prosocial defaults. Exploratory cluster analyses showed that around 75% of participants made choices based on their social preference, thereby showing little to no response to defaults. The remaining 25%, however, were responsive to defaults, resulting in an overall higher fraction of prosocial choices made when defaults are prosocial (vs. selfish). Overall, despite most participants being non-responsive, findings highlight the aggregate benefit of setting prosocial defaults, both in distracting and non-distracting environments.

How do people attribute responsibility when an outcome is not caused by an
individual but results from a decision chain involving several people? We study
this question in an experiment, in which five voters sequentially decide on how to
distribute money between them and five recipients. The recipients can reward or
punish each voter, which we use as measures of responsibility attribution. In the
aggregate, we find that responsibility is attributed mostly according to the voters’
choices and the pivotality of the decision, but not for being the initial voter. On
the individual level, we find substantial heterogeneity with three overall patterns:
Little to no responsibility attribution, pivotality-driven, and focus on choices. These
patterns are similar when praising voters for good outcomes and blaming voters for
bad outcomes.

Politics is increasingly driven by identity cleavages, which also affect the discussion about inequality and redistribution. Typically, redistribution is meant to reduce inequality, implying that redistribution neither makes the rich richer nor the former poor the new rich. However, if identity affects redistribution, these limits might no longer be binding, and redistribution could further increase existing inequalities (making the rich richer) or reverse the income ordering to favor the once-poor (which can even be inequality increasing if redistribution is strong). In a laboratory experiment, we investigate redistribution via a novel smooth one-dimensional distribution mechanism that also allows for an increase or reversal of inequality. Decision-makers receive information about the recipients’ political orientation, nationality, or seat number during the experiment, and we vary the structure and source of income inequality (income is either earned, random, or unfair). We find most choices of the decision-makers involve redistribution, with only 8 % of choices sticking with the status quo. While most redistribution choices reduce inequality, a larger share—(18 %)—increase inequality by making the rich richer, 13 % of choices reduce overall inequality but make the poor the new rich, and 9 % increase inequality by making the poor very rich. Thus, 40 % of decisions are redistributions that are typically unobserved in common redistribution designs. Ingroup favoritism is a strong motive for redistribution in general, and it is the most important motive for redistribution to increase or reverse inequality. Indeed, 85 % of the inequality-increasing or reversing decisions favor the ingroup. Complementary eye-tracking data show that decision-makers’ attention to information about the recipients’ groups and to poor outliers are related to higher levels of redistribution.

Organizational decisions are often made by groups rather than individuals. Depending on the group composition, each member’s characteristics—like gender and motivated beliefs—can influence the final group investment decision. To capture this, we design two types of investment situations in a randomized controlled laboratory experiment—one with fixed chances of success and one with performance-dependent chances of success. This novel design entails the perceived ability to “beat the odds” of the investment and thus models real-life investment situations more accurately than standard lottery choice. Our results demonstrate the benefits of mixed group composition in terms of both gender and overconfidence: Groups with all men and/or all overconfident group members consistently overinvest when a possibility to “beat the odds” is present, but not in standard situations. We explore several channels for our results and find that (i) individual probability perception, (ii) leader responsibility allocation and (iii) spillover effects from priming show significant effects.

People often have to judge the social motives of others, for example, to distinguish truly prosocial people from those merely trying to appear prosocial. Gaze can reveal the motives underlying social decisions, as decision-makers dedicate more attention to motive-relevant information. We extend the use of eye-tracking and apply it as a communication device by providing (real-time) eye-tracking information of one participant to another. We find that untrained observers can judge the prosociality of decision-makers from their eye-tracked gaze alone, but only if there are no strategic incentives to be chosen for a future interaction. When there are such strategic incentives, the cues of prosociality are invalidated, as both individualistic and prosocial decision-makers put effort into appearing more prosocial. Overall, we find that gaze carries information about a person’s prosociality, but also that gaze is malleable and affected by strategic considerations.

It is a widely held belief that people’s choices are less sensitive to changes in value as value increases. For example, the subjective difference between $11 and $12 is believed to be smaller than between $1 and $2. This idea is consistent with applications of the Weber-Fechner Law and divisive normalization to value-based choice and with psychological interpretations of diminishing marginal utility. According to random utility theory in economics, smaller subjective differences predict less accurate choices. Meanwhile, in the context of sequential sampling models in psychology, smaller subjective differences also predict longer response times. Based on these models, we would predict decisions between highvalue options to be slower and less accurate. In contrast, some have argued on normative grounds that choices between highvalue options should be made with less caution, leading to faster and less accurate choices. Here, we model the dynamics of the choice process across three different choice domains, accounting for both discriminability and response caution. Contrary to predictions, we mostly observe faster and more accurate decisions (i.e., higher drift rates) between high-value options. We also observe that when participants are alerted about incoming high-value decisions, they exert more caution and not less. We rule out several explanations for these results, using tasks with both subjective and objective values. These results cast doubt on the notion that increasing value reduces discriminability.

In everyday life, we have to make decisions under varying degrees of risk. Even though previous research has shown that the manipulation of sleep affects risky decision-making, it remains unknown whether individual, temporally stable neural sleep characteristics relate to individual differences in risk preferences. Here, we collected sleep data under normal conditions in fifty-four healthy adults using a portable high-density EEG at participants’ home. Whole-brain corrected for multiple testing, we found that lower slow-wave activity (SWA, an indicator of sleep depth) in a cluster of electrodes over the right prefrontal cortex (PFC) is associated with higher individual risk propensity. Importantly, the association between local sleep depth and risk preferences remained significant when controlling for total sleep time and for time spent in deep sleep, i.e., sleep stages N2 and N3. Moreover, the association between risk preferences and SWA over the right PFC was very similar in all sleep cycles. Because the right PFC plays a central role in cognitive control functions, we speculate that local sleep depth in this area, as reflected by SWA, might serve as a dispositional indicator of self-regulatory ability, which in turn reflects risk preferences.

There are many situations where resources are distributed between two parties and where the deciding party has information about the initial distribution and can change its outcome, for example, the allocation of budget for funds or bonuses, where the deciding party might have self-interested motives. Although the neural underpinnings of distributional preferences of resources have been extensively studied, it remains unclear if there are different types of distributional preferences and if these types underlie different disposing neural signatures. We used source-localized resting EEG in combination with a data-driven clustering approach to participants’ behavior in a distribution game in order to disentangle the neural sources of the different types of distributional preferences. Our findings revealed four behavioral types: Maximizing types always changed initial distributions to maximize their personal outcomes, and compliant types always left initial distributions unchanged. Disadvantage-averse types only changed initial distributions if they received less than the other party did, and equalizing types primarily changed initial distributions to fair distributions. These behavioral types differed regarding neural baseline activation in the right inferior frontal gyrus. Maximizing and compliant types showed the highest baseline activation, followed by disadvantage-averse types and equalizing types. Furthermore, maximizing types showed significantly higher baseline activation in the left orbitofrontal cortex compared to compliant types. Taken together, our findings show that different types of distributional preferences are characterized by distinct neural signatures, which further imply differences in underlying psychological processes in decision-making.

The act of punishing unfair behavior by unaffected observers (i.e., third-party punishment) is a crucial factor in the functioning of human societies. In everyday life, we see different types of individuals who punish. While some individuals initiate costly punishment against an unfair person independently of what other observers do (independent punishers), others condition their punishment engagement on the presence of another person who punishes (conditional punishers). Still others do not want to partake in any sort of punishment (nonpunishers). Although these distinct behavioral types have a divergent impact on human society, the sources of heterogeneity are poorly understood. We present novel laboratory evidence on the existence of these three types. We use anatomical brain characteristics in combination with stated motives to characterize these types. Findings revealed that independent punishers have larger gray matter volume in the right temporo-parietal junction compared to conditional punishers and nonpunishers, an area involved in social cognition. Conditional punishers are characterized by larger gray matter volume in the right dorsolateral prefrontal cortex, a brain area known to be involved in behavioral control and strategic reasoning, compared to independent punishers and nonpunishers. Finally, both independent punishers and nonpunishers are characterized by larger gray matter volume in an area involved in the processing of social and monetary rewards, that is, the bilateral caudate. By using a neural trait approach, we were able to differentiate these three types clearly based on their neural signatures, allowing us to shed light on the underlying psychological mechanisms.

We present an interactive eye-tracking study that explores the strategic use of gaze. We analyze gaze behavior in an experiment with four simple games. The game can either be a competitive (hide & seek) game in which players want to be unpredictable, or a game of common interest in which players want to be predictable. Gaze is transmitted either in real time to another subject, or it is not transmitted and therefore non-strategic. We find that subjects are able to interpret non-strategic gaze, obtaining substantially higher payoffs than subjects who do not see gaze. If gaze is transmitted in real time, gaze becomes more informative in the common interest games and players predominantly succeed to coordinate on efficient outcomes. In contrast, gaze becomes less informative in the competitive game.

People differ in whether they like to be in control of a decision or whether they would happily delegate a decision. We explore the heterogeneity and the underlying factors of the participants’ values of decision-making power in an allocation choice between a fair and an unfair option. This allocation decision affects the outcomes of the deciding person and three other people in different ways. We find that people differ in their preference for keeping this social decision, and more than 85% never pay for delegating the choice. The value for keeping the decision-making power is affected by the strength, but not the direction of social preferences, and relates to the preference for keeping a useless decision, i.e. selecting the winning number of a lottery. The value of decision-making power is reflected in response times and both eye- and mouse-tracking.

This study contributes to the understanding of how individuals make choices for themselves and on behalf of others in a risky environment. In a laboratory eye-tracking experiment, we investigate whether risk preferences, decision error, and information processing differ between decisions made for oneself and on behalf of others. While we find no differences in risk preferences when deciding for oneself or for someone else, individuals have a greater decision error when deciding for others. Process data partly explains these differences. Individuals spend less time, have less fixations, and inspect less information when deciding for others. We detect similar processing patterns when comparing intuitive and deliberative decision making. We argue that the processing of decisions for oneself is more effortful and involves more extensive deliberation which, in turn, is related to less decision errors.