Why Do Children Punish Unfairness?

iStock image by Yurii Klymko licensed to Art Markman

There are many ways to influence the behavior of other people. Broadly speaking, we can reward others for their good behavior and punish people for their bad behavior. These strategies are ones that children learn early on, and even 5-year-olds are adept at punishing others for doing something wrong.

There are lots of actions that a child might want to punish. For example, when one person is mean to another, it's an offense that may lead to a punishment. An interesting example of a behavior that may lead to punishment is unfairness. There is a strong social norm that people should share things with others. Indeed, American parents spend a lot of time teaching children to share what they have (like their toys) with others.

Children will punish others who do not share with others, but there is some question about why they do this. One possibility is that children learn a rule that being unfair is wrong and then they feel compelled to punish that behavior. Another possibility is that children are more strategic. Children may know that if someone they are likely to encounter does something unfair, that individual is likely to be unfair to them, as well, unless they are punished.

These possibilities were explored in a paper by Young-eun Lee, Susan He, and Felix Warneken published in the Journal of Experimental Psychology: General in 2024.

In these studies, children between the ages of 5 and 9 were first given 20 coins and were told these coins could be exchanged to watch fun videos. Then, the children were told they would see two other children playing a game that involved similar coins.

In the game they watched, one player was the divider, and the other was the recipient. The divider was given six coins and was told to split them with the recipient in any way they wanted. On some trials, the divider was selfish, keeping all six coins and giving none to the recipient. In other trials, the divider was fair and split the coins evenly, keeping three and giving three to the recipient. Through eight rounds in the game, the divider split the coins fairly twice and unfairly six times.

After watching the divider choose a split for the coins, the participant was given the option to punish the divider. Choosing to punish the divider would cost the participant a coin (the punishment would reduce the number of videos the participant would get to see later). If they issued a punishment, neither the divider nor the recipient would get any coins. Because the unfair split was always six coins to the divider and 0 coins to the recipient, punishing the divider would never harm the recipient.

Finally, before watching the game, participants were told they would play the sharing game next as a recipient. Some children were told they would play the sharing game with the same divider as they were watching. Others were told they would play with a different divider than the one they were watching. The experimenters ensured that the participants understood all of these instructions.

The idea here is that if children punish unfairness, they should punish the unfair division of coins, but not the fair division of coins. If children punish unfairness to ensure that they are treated fairly by a person in the future, they should be more likely to punish the divider when they play with that same person later than if they are not. Finally, if they punish unfairness in general, they should punish unfair allocations by the divider regardless of whether they would play with that person later.

The results of this study, and a similar replication reported in the same paper, found that children punish the unfair allocations about half the time and rarely punish the fair allocations. Children clearly understood the game and tended to punish unfairness. There was no clear difference between the likelihood of punishing unfairness and whether the child was slated to play that child or another in the next game. This finding suggests that children are not being highly strategic when they punish others for unfairness and they do it only when it might benefit them later.

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This work suggests that children are learning a general rule that unfairness is bad and that people who act unfairly toward others should be punished. Interestingly, the punishment in this study had a cost to the participants—watching fewer videos the more times they punished the unfairness. Despite that cost, participants did feel the need to punish unfair divisions.