When Rule-Breaking Spreads, Who Keeps the Line?

A new study suggests that rule-breaking by a few people can spread through a group, especially when others see someone like them getting away with it. According to Science News, researchers reported October 21 in Proceedings of the Royal Society B that a small number of people willing to push beyond a rule can move others toward breaking it too.

That matters because many rules depend on more than police, teachers, referees or cameras. Speed limits, hallway behavior, online comments and crowd conduct all rely partly on the belief that most people will stay within the line. The study asks a difficult question: when people see rule-breaking rewarded, do they treat the rule as weaker, or do they keep following it anyway?

The researchers, led by Lucas Molleman, a psychologist at the University of Amsterdam, designed an online experiment with 750 participants in the United States. The timing was deliberate: the experiment took place a week before the 2024 U.S. presidential election, when political identity was likely to feel especially strong. About half the participants identified as Democrats and about half as Republicans.

The task itself was simple. Participants watched an animated shooting star move across a row of 100 squares. Then they had to choose which square shone the brightest. The brightest square always appeared near the middle of the row. But the payment system created a temptation: participants earned more money for choosing squares farther to the right. The farthest-right square paid roughly the equivalent of $1.30.

In other words, the experiment separated the rule from the reward. The rule was to answer accurately by picking the brightest square. The reward pushed people toward a less accurate answer. A person who chose the far-right square was not just making a mistake; that choice reflected a willingness to ignore the task’s rule for a larger payoff.

Initial tests found that dedicated rule followers and rule breakers each made up about one-fifth of the group. Then the researchers added a social cue. As participants repeated the task, they received information about a previous respondent, including that person’s political affiliation and how closely that person had followed the rule.

Seeing a rule follower did not strongly produce more rule following, even when the earlier person shared the participant’s political party. But seeing a rule breaker had a stronger effect. When participants learned that someone with the same political leaning had chosen the most profitable option, they became more likely to shift rightward themselves. Without that social cue, participants chose the farthest-right square about 23 percent of the time. After hearing that a political ally had made the most lucrative choice, that rose to almost 40 percent.

The political part of the experiment is important, but not because the study says one party breaks rules more than the other. The point is that identity can make behavior feel more acceptable. If a stranger breaks a rule, a person might judge it harshly. If someone on “my side” does it, the same act can start to look normal, strategic or forgivable.

The researchers then used a computer simulation, a model that imitates a process so scientists can test possible patterns over time. They created a digital version of each participant and had those versions interact in groups of 100. In some simulated groups, a small number of people who escalated beyond the previous level of rule-breaking could pull the whole group toward much more extreme behavior. But when the group included about the same share of dedicated rule followers as the real experiment, overall rule-breaking settled at a more moderate level.

That finding creates the central tension. On one side, the study suggests that a few people can matter a lot. Rule-breaking may not need a majority to spread; it may only need visible examples, rewards and a sense that “people like us” are doing it. On the other side, the same study suggests that firm rule followers can slow the spread. A group is not helpless just because some members push the limits.

Not everyone thinks the experiment can be stretched too far. Science News quoted Eugen Dimant, a behavioral economist at the University of Pennsylvania, who was not involved in the research, saying, “But that’s not how the world works.” His point was that real life includes consequences and pressures the experiment left out. Drivers may fear tickets, students may fear losing privileges, and crowds may be shaped by social norms, which are shared expectations about how people are supposed to behave.

Molleman also acknowledged that reality is more complex. The value of the experiment is that it strips a situation down to a few parts: a rule, a reward for bending it, and information about what someone else did. That simplicity helps show a possible mechanism, or cause-and-effect pathway, behind behavior that can be much messier in real life.

The study does not prove that every broken rule spreads like a virus. It does not show what happens when punishments are visible, when the rule is viewed as unfair, or when people have strong moral reasons to disobey. But it does suggest that rule-breaking is not only an individual choice. It can become social information. Once people use others’ behavior as evidence of what is acceptable, a rule can weaken even before anyone officially changes it.