Perceptions of blame and due punishment in group transgressions

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In 44 BCE, Roman senators acting in concert stabbed Julius Caesar more than 20 times at a senate meeting. Similar group murders have happened throughout history. In the 17th century, for instance, about 15 co-conspirators stabbed Nader Shah, an influential Iranian monarch, to death. Such cases are not confined to history books either. Collective crimes and other moral violations take place in societies today, and it is by no means only the powerful who are the victims. Gang rapes, hate crimes, and conspiracies are examples of collective offenses that hit the headlines in our times.

Established law is one thing, but how do we – as laypeople in legal matters – judge the seriousness of transgressions and the share of blame to be attached to the individual perpetrators? Do we tend to attribute less guilt, and therefore hand out milder punishments, to a group offender compared to a solo violator? Do we carve up the blame, so to speak, and apportion the pieces? A team led by LMU neuroscientist Dr. Anita Keshmirian investigated these questions. The international group of researchers, which also included LMU academics Prof. Dr. Ophelia Deroy, Chair of Philosophy of Mind, psychologist Dr. Bahador Bahrami, and scholars from Harvard University and Brown University, has studied whether and, if so, why we apply double standards in our everyday judgments.

In a series of experiments, the researchers asked hundreds of randomly assigned subjects to rate how harshly one should punish the same individual when they committed a similar moral transgression, either alone or with others. The transgressions covered a wide variety of different offenses. It was already known from earlier research that people feel less responsible for harm they cause in conjunction with others. However, the literature has focused on the judgments of people who were involved in the violations.

A fundamental aspect of how we understand causes and effects

But what happens when disinterested third parties are asked to evaluate a transgression and determine the harshness of the punishment? The new study has shown that they, too, tend to treat group perpetrators with greater leniency. Known as “diffusion of punishment,” this inclination to spread out punishment, as it were, seems to have deep roots in our thinking about morality.

According to lead author Keshmirian, the findings of the study have practical ramifications for the justice system, with jury trials being a prime example. In most legal models, each and every perpetrator of a collective action is considered fully responsible for any harms caused and is therefore expected to be punished just as harshly or mildly as a solo violator. But the study demonstrates that these prescriptions deviate from what laypeople see as fair punishment. This may lead to miscarriages of justice in jury trials. Moreover, such discrepancies could erode confidence in the justice system.

But how do such deviations arise? The answer, the researchers found, lies in a fundamental aspect of how we understand causes and effects: When there are multiple causes for an effect, we tend to reduce the estimated contribution of each. For example, if two parents neglect a child, the causal responsibility for the damage caused is divided between them, as if we automatically assume that some unknown proportion of the impact was caused by one person and the rest by the other. If this thought pattern explains the sharing out of responsibility and hence the diffusion of punishment, we would expect to see diffusion only when the perpetrators actively cause a concrete negative outcome for their victim. The experiments confirmed this suspicion.

In the first experiment, respondents assigned less punishment to members of groups who caused deaths either intentionally or accidentally. In failed murder attempts, on the other hand, people punished solo and group offenders equally. The researchers inferred that mere intent – regardless of malice – does not lead to diffusion of punishment, in that it does not actually inflict harm, the causal responsibility for which can be distributed.

To confirm this interpretation, the scientists asked respondents to judge two more scenarios: One concerned the causing of bodily harm while the other related to a crass violation of moral norms for which there were no victims and therefore no concrete harm was caused. Participants found both cases punishment-worthy. But whereas the respondents once again voted to share out the responsibility in the case of a group assault causing bodily injury, they saw no direct harm in the second case that they could causally blame on the perpetrators. “This shows,” explains Anita Keshmirian, “that causality and its estimation are fundamental to the way we perceive the world, inclucing morality.”

Anita Keshmirian, Babak Hemmatian, Bahador Bahrami, Ophelia Deroy, and Fiery Cushman: Diffusion of punishment in collective norm violations. Scientific Reports 2022