An in-group is a group of people who identify with each other based on a variety of factors including gender, race, religion, or geography. Our tendency to distinguish between in-group and out-group members has moral implications.

People may harm those whom they perceive to be in an out-group in ways that they would not harm in-group members. For example, one study showed that when soccer fans viewed fans of their own team being harmed, they felt empathy. But when they viewed fans of a rival team being similarly harmed, they felt pleasure.

Likewise, people tend to make different moral judgments based on in-group and out-group distinctions. When someone in our in-group misbehaves, the natural reaction is often to dismiss the behavior as no big deal. But when someone in our out-group does the same thing, we will tend to judge the behavior much more harshly.

Indeed, when automatic in-group and out-group distinctions replace conscious and thoughtful reflection, we are more likely to harm one another and behave unethically.