This article originally appeared on " The Monkey Cage " in The Washington Post and was published on The Psych Report before it became part of the Behavioral Scientist in 2017.

As the Gaza-Israel conflict began escalating last month, there were widely circulated reports that Israeli spectators had gathered on garden chairs and old sofas to cheer as bombs rained down on people living in Gaza just a few miles away. This expression of malicious glee is hardly unique to Israelis; Palestinians have also been seen standing on rooftops and celebrating when Hamas fires rockets at cities in Israel.

Though these displays of Schadenfreude—in which people exhibit pleasure at others’ pain—often garner widespread condemnation, records indicate they have a long history. According to some accounts, people similarly sat in chairs on hillsides and watched the slaughter unfold during the American Civil War. A poem published in the Boston Herald in 1861 vividly captured the revelry:

Have you heard of the story so lacking in glory,

About the Civilians who went to the fight,

With everything handy, from sandwich to brandy,

To fill their broad stomachs and make them all tight.

There were bulls from our State street, and cattle from Wall street,

And members of Congress, to see the great fun;

Newspaper reporters (some regular shorters)

On a beautiful Sunday went out to Bull Run.

New research in social psychology helps explain these responses and offers one way we can help restore empathy for our enemies.

In a forthcoming paper in the Journal of Experimental Social Psychology, with our colleagues Emile Bruneau and Rebecca Saxe at MIT, we found evidence that this intergroup empathy gap—the tendency not only to empathize less with out-groups, but also to feel pleasure in response to their pain—is a consequence of basic group dynamics.

In a series of experiments with almost 500 participants, we found that creating two groups and putting them in direct competition with one another was sufficient to reduce their empathy for out-groups and induce a sense of joy when members of the out-group suffered misfortune.

In our experiments, we told participants that we were interested in assessing problem solving in teams. Participants were promised $1 for their time, but they stood to double their winnings in their team won the problem solving challenge. Participants were then randomly assigned to one of two novel groups—the Eagles or the Rattlers. Unlike the entrenched conflicts in the Middle East and US Civil War, the arbitrary and trivial nature of these groups ensured there was nothing intrinsically different between the members of each group.

We then told participants they would have the opportunity to learn about the other players from both groups before completing the problem solving challenge. Participants were presented with 16 scenarios depicting positive (e.g., Bill found a $5 bill on the street) and negative (e.g., Brandon accidentally walking into a glass door) events in the lives of in-group and out-group members. After reading about each event, participants answered two simple questions: “How bad does this make you feel?” and “How good does this make you feel?”

The results indicated that participants experienced greater empathy (i.e., feeling worse about negative events and better about positive events) for in-group compared to out-group members. Our participants also experienced greater counter-empathy (i.e., feeling better about negative events—known as Schadenfreude—and worse about positive events—known as Gluckschmerz) for out-group compared to in-group members. More strikingly, this intergroup empathy gap was driven by out-group antipathy (diminished empathy toward the out-group relative to any other group), rather than extraordinary empathy for the in-group (feeling greater empathy for the in-group relative to any other group).

In other words, participants in these completely arbitrary groups appeared to experience a similar pattern of intergroup empathy bias to that observed among Israelis and Palestinians and other groups in the midst of violent, intractable conflicts. In fact, other research with Israeli and Arab participants has found similar results. These counter-empathic responses matter because they are typically associated with greater discrimination, a greater willingness to harm, and a reduced willingness to engage in costly helping.

Given the serious negative consequences associated with intergroup empathy bias, we tried to design an intervention to restore empathy towards the out-group. This turned out to be far more difficult than we initially expected. For instance, informing participants that their team had pulled ahead in points or won the challenge had virtually no effect on intergroup empathy bias. Participants still reported greater empathy for in-group members and greater Schadenfreude for out-group members, even after they received information signaling that the out-group was no longer a threat.

In a final effort to decrease intergroup empathy bias, we presented participants with cues that signaled reduced cohesion, or “groupy-ness”, within the two competing groups.

In this experiment, participants were randomly assigned to see different images of the social networks comprised of the two teams. Some participants saw an image of two segregated social networks indicating that members of the Rattlers and Eagles were closely connected to fellow in-group members but not out-group members (i.e., two small clusters far removed from one another). Other participants saw an image of a integrated social network indicating that members of the Rattlers and Eagles were interconnected with one another (i.e., one large cluster).

Participants who thought the two teams were interconnected with one another reported greater empathy for the out-group. Merely making people aware that the members of each group are not monolithic in their social connections may be one way to help restore empathy in intergroup conflicts.

It would be naïve for us to suggest that this simple intervention could resolve the violent conflict in Gaza. The fact that Israelis and Palestinians are increasingly socially and physically segregated may make such an intervention very difficult to implement. Even our use of social media seems to mirror this segregation: “pro-Palestinian” activists and media outlets are closely connected to one another and the same is true of “pro-Israeli” activists and media outlets. The problem is that there is very little connection between the two groups and information is unlikely to pass between them.

Thankfully, this does not have to be the case. A recent study on Israelis and Palestinians teenagers who were brought together as part of a summer program called Seeds for Peace offers reason for hope. Campers who made friends outside their own group developed positive feelings towards all members of the out-group, and were likely to retain those feelings long after returning home. By removing campers from the social pressures of home, they were able to forge new social networks and increase their empathy with the other side.