Episode 44: The Contact Hypothesis

How can we make the world less prejudiced? Research from the social sciences hints at a promising solution. This week, we do a deep dive on “The Contact Hypothesis”: what it is, how we know it works, and what its limits are.

We hear from four experts in this area whose research sheds light on the question:

  • Tom Pettigrew, emeritus professor of psychology at University of California, Santa Cruz
  • Linda Tropp, professor of social psychology at University of Massachusetts-Amherst
  • Shreya Bhattacharya, economist; PhD from the University of Houston
  • Salma Mousa, assistant professor of political science at Yale University


Download a PDF version of this episode’s transcript.

Note: Minor changes to this episode’s script arose in editing.

In June 2014, insurgents from the extremist group, ISIS – the Islamic State of Iraq and Syria – stormed into the city of Mosul in northern Iraq, defeating the Iraqi Army and taking control of the city. 

SALMA MOUSA: And that campaign involved ethnic cleansing of religious minorities, primarily Yazidis, but also smaller numbers of Christians and Muslim groups as well, who were forcibly displaced basically overnight and who would remain displaced for two or three years, even though they thought they would be home after the weekend.

That’s Salma Mousa. She’s a political science professor at Yale. In 2014, she watched the news of ISIS in Mosul from her home in California. She may have been geographically far away at the time…

SALMA MOUSA: But it’s not a topic that was ever that far from home for me. I’m from Egypt. I grew up in the Middle East, almost my entire life. I did my undergrad there. My school was bombed by Al-Qaeda when I lived in Saudi Arabia. I was out of school for a few months. So this is not like, unfortunately it’s not like a new topic for me. I’m not going to say my family’s affected as much as other people’s, but, it’s something that’s in the periphery and it’s something you’re kind of familiar with, like this kind of extremism and… But you never really see it take root like ISIS took root. I think like lots of other people, we kind of saw ISIS and thought, okay, this is like an Al-Qaeda branch. And sometimes they take over a few neighborhoods at a time in Iraq, but it doesn’t last for more than a few days or a few weeks. And then they’re going to be just stamped out by the army, by the local police. And this was really different. All of a sudden you’re seeing these scenes where Mosul fell. Like Mosul—one of the biggest cities in Iraq—it just fell, and I could not believe my eyes that ISIS took over a city that big and that important and held onto it for so long. 

When ISIS seized Mosul, thousands of Christians fled, many taking refuge in Iraq’s northern Kurdish region. This was just the latest chapter in Christian life in this country. Since the US overthrew Saddam Hussein in 2003, there’s been a marked shift in Christian-Muslim relations there. Twenty years ago, nearly 1.5 million Christians lived in Iraq but now only a few hundred thousand still live within the country’s borders. As the Associated Press puts it: the Christian people “who remain in Iraq feel abandoned, bitter, and helpless, some wary of neighbors with whom they once shared feasts and religious celebrations, Muslims and Christians alike.”[1]

Around the time ISIS took over Mosul, Salma Mousa had just started as a PhD student in Stanford’s political science department. As she watched the events play out, she wondered whether there was anything she could do to help the area move forward.

SALMA MOUSA: And I just thought like, I personally care about this topic because I want the Middle East to be diverse. The Arab world has always been a diverse place. And to see it be emptied of its ethnic and religious diversity for me is, is a really deep, personal tragedy at just a national– At every single level, it’s a tragedy, and I want to do everything I can to preserve that social fabric and that diversity that’s always characterized the Middle East. So when I saw this happening, I thought, okay, we need to get to work on this. I’m not going to fix Iraq in a day, but what are some of the things that are happening on the ground that people are trying to do to fix this? Like how can we possibly think about moving forward after this kind of tragedy and what can research, uh, tell us about it?

You’re listening to Opinion Science, the show about our opinions, where they come from and how they change. I’m Andy Luttrell. And we’ll hear about Salma Mousa’s research in Iraq in a little bit, but we need to lay some ground work first.

This week we’re going to dive deep into a concept in social science called the contact hypothesis. It’s probably the most thoroughly studied tool for addressing prejudice, and it’s been explored for decades by people all over the world. We’ll hear from experts in psychology, political science, economics, and sociology as we unpack what the contact hypothesis is, whether it actually works, and what its limitations are.

Now, social relations are super complex, and I won’t even try to explore every issue relating to racism, social class, religious conflict, and all the other ways discrimination rears its ugly head. But to me, the seed at the center of a lot of this stuff—and what makes it relevant to this show—is the notion of prejudice. At its most basic, prejudice is an opinion we form of an entire group of people. Someone who thinks negatively of religious minorities, for example, has a prejudice. And these general prejudices about groups can spill over into how we think about and act toward individual people from those groups, unfairly giving advantages or disadvantages to someone not because of who they are but because of how we label them.

Now, our prejudices come from all sorts of places, but one of the nagging problems is that we usually don’t really know the people we have prejudices about. So maybe—just maybe—the key to stopping prejudice in its tracks is just bringing people together. That’s the gist of the contact hypothesis, but let’s unpack it a little more…

Act I: Origins

Gordon Allport and The Nature of Prejudice

There’s no person more tied to the contact hypothesis than Gordon Allport. He was born in 1897 in Montezuma, Indiana. By the time he finished high school, his brother, Floyd, was working on a PhD in psychology at Harvard University and encouraged Gordon to apply to Harvard for college. I’m sure they had no idea that Harvard would become Gordon’s home—he finished his undergraduate degree there, then completed a PhD there in just two years! A couple years later, he returned to Harvard as a social science instructor, then as a professor, and he stayed there for the rest of his career.

Anyhow, in 1954, Gordon Allport published a book called The Nature of Prejudice containing 31 chapters exploring prejudice and where it comes from. In fact, they even released an abridged paperback version—you could buy it at the airport—and it became a best-selling social psychology book in the public. Allport once said that the book was his proudest achievement[2], and reflecting on the influence of the book fifty years later, a group of psychologists seemed to agree, writing: “There is no debate that Gordon W. Allport’s The Nature of Prejudice is the foundational work for the social psychology of prejudice… [H]alf a century after its publication, [it] remains the most widely cited work on prejudice.[3] Almost seventy years ago, Allport created the roadmap for how we still think about these issues today.

What’s interesting, though, is that by his nature, Allport was a personality psychologist. It’s thanks to him that the study of personality ever blossomed into what it is today. But it meant that a lot of The Nature of Prejudice skirts around the social side of the equation. 

TOM PETTIGREW: He was first a personality psychologist, second, a social psychologist. And, uh, he didn’t think too much of sociology. He thought there must be something to it, he once said to me, but he didn’t understand it. But, for him, causation came from individuals, emanated from people.

That’s Tom Pettigrew. He was a graduate student at Harvard, working with Allport in the years leading up to the book. In those days, it was his job to fetch books at the library for Allport as he was doing the research. We’ll get back to Tom’s story in a second, but despite what he says about Allport’s orientation as a personality psychologist, one place where social influences get the spotlight is Chapter 16: The Effect of Contact.

Okay, so what do we mean by “contact”? Well, deciding what counts as contact and what doesn’t can get a little fuzzy, but we’re basically talking about bringing people together from different backgrounds. This could be as simple as just increasing your exposure to people from different groups, although some researchers don’t think that’s quite enough to count as true “contact.” More often what we mean is creating opportunities for social interactions between individual people who differ in things like their race or religion. One recent report used the term “meaningful social mixing,” which I think captures the spirit of what contact is supposed to be.[4]

Just a quick terminology check before we move on. In the social sciences, we often lean on this term, “intergroup.” Our point is that each of us belongs to different groups. We get our identities from them, and we’re often quick to categorize other people based on them. And when I say “group,” I don’t mean like the handful of people you get lunch with—I mean big socially identifying groups. These include the kinds of identifiers that end up on surveys—gender, race, age group—among other things we use to categorize ourselves—religion, sexual orientation, disability status, hair color, etc.

So, intergroup contact is about interactions across these group lines—White and Black people working together in an office, Christians and Muslims playing on the same sports team, Cis and Transgender people having an engaged conversation.

Now, back in the early 20th century, the assumption was actually that contact would only make intergroup tensions worse. It seemed like hostility was a given, so why rock the boat? One sociologist even wrote in 1934 that bringing people together from different racial groups would only breed “suspicion, fear, resentment, disturbance, and at times open conflict.”[5]

But then there was some reason to rethink that assumption. During World War II, the United States Army made it a policy that White and Black soldiers would fight separately. No mixed units allowed. But the realities of war called for a change of plans. Infantry replacements were sorely needed, and the Army decided to replace various White platoons with Black platoons and suddenly Black and White soldiers were fighting side by side. Was it the social disaster that early sociologists feared?

Well, as one platoon sergeant from South Carolina said:

“When I heard about it, I said I’d be damned if I’d wear the same shoulder patch they did. After that first day when we saw how they fought, I changed my mind. They’re just like any of the other boys to us.”

A company commander from Nevada said:

“You might think that wouldn’t work well, but it did. The white squad didn’t want to leave the platoon. I’ve never seen anything like it.”

And a platoon commander from Texas put it even more plainly:

“We all expected trouble. Haven’t had any.”

Surveys from Army’s Research Branch tell a similar story. When they asked white soldiers in units that remained segregated, only 18% thought it would be a good idea to mix Black and White platoons. But when they asked white soldiers who had already been made to mix with Black soldiers, 64% said mixing platoons was a good idea.[6]

Then in 1945, the Social Science Research Council established a committee to explore techniques for reducing intergroup hostility. They asked Robin Williams to prepare a report. I know—not that Robin Williams. I’m talking about Robin Williams, Jr., a sociologist at Cornell University. He produced a report suggesting more than 100 propositions and testable hypotheses for improving intergroup relations. One of them—#78—highlighted the potential benefits of intergroup contact. He outlines a few considerations for what would boost the effectiveness of contact, but that was that.

TOM PETTIGREW: It was just a couple pages in a book of his that he put this down, but Allport was impressed by it and cites him in his nature of prejudice book.

As Allport’s writing his tome on prejudice, he happens across Williams’ ideas and the research on integrated units in the military, and voila…we have Chapter 16 on The Effect of Contact, which he introduces by writing:

It has sometimes been held that merely by assembling people without regard for race, color, religion, or national origin, we can thereby destroy stereotypes and develop friendly attitudes. The case is not so simple.[7]

Because the prevailing view at the time was that contact would only make prejudice worse, Allport was careful to outline the pieces that would have to be in place for contact to actually be beneficial. Now almost every textbook covering the contact hypothesis comes with four general conditions that theoretically must be met for contact to reduce prejudice.

#1. Equal Status. Even if two groups have different status in society, bringing them together should only reduce prejudice if those groups have equal status within the contact situation. That is, one person shouldn’t be the leader and the other the follower, one the boss and the other the employee. It’s only when they come together on an even playing field that we should expect to see the benefits.

#2. Common Goals. The people who are getting together should share the same goals. Imagine a football team—everyone on the team wants to win.

#3. Cooperation. It’s one thing to have the same goals, but the people who are interacting need to cooperate toward reaching those goals. If one person’s doing all the work—or worse, there’s active competition for the same goal, we shouldn’t expect to see much good come of this kind of contact.

#4. Institutional Support. It should be clear that the folks in charge support social mixing and the reduction of prejudice. Laws and customs shouldn’t get in the way. For example, trying to promote intergroup contact wouldn’t seem to have much impact when there are official segregation policies in place.

And there we have, the Contact Hypothesis—an idea with some straightforward origins that would become the most studied method for reducing prejudice.

Tom Pettigrew’s Impact

Even though it’s Allport’s name that’s been stuck to the Contact Hypothesis for decades, I’d argue that it’s actually Tom Pettigrew—his former grad student—who’s been the most ardent champion of intergroup contact.

Tom grew up in Richmond, Virginia in the 30s and 40s. Not a time or a place with super progressive views on race. In his new book, Tom writes that “slavery was never once discussed in [his] … public schooling.”[8] But thanks to a handful of personal experiences with African Americans growing up, Tom had seen through the thin veil meant to keep racism alive. And he didn’t keep his opinions to himself. He was expelled in 7th grade for calling his history teacher a bigot after she routinely disparaged African Americans. Then years later when he was doing research on apartheid in South Africa, he was told by a government official that he was no longer welcome in the Union of South Africa. In response, he said: “Why sir, that’s the biggest compliment I’ve ever received.”[9]

In the 60s, he was a vocal advocate for racial desegregation in American schools, giving speeches, writing popular articles, and serving as an expert witness in various court cases. He even hosted a 15-part public television series in 1962 called Epitaph for Jim Crow: The Dynamics of Desegregation.[10]

ANNOUNCER [TV clip]: The Dynamics of Desegregation

TOM PETTIGREW [TV clip]: Race relations are the most important domestic problem facing our nation today. We’re going to take a new look at race relations and see if we can clear up some of these misconceptions, using the tools and techniques of the sociologist and the social psychologist.

But let’s back up—it was in 1952 that he arrived at Harvard as a graduate student to work with Gordon Allport, who was in the thick of his research for the big book on prejudice. I asked Tom what Allport was like as a person.

TOM PETTIGREW: He was a tall man. He was actually shy. He was warm, but shy. He certaintly wasn’t shy in his writings. He was intellectually confident, but socially, quite a bit shy. And he had trouble expressing hostility, and I have no such trouble. And, he liked me in part because I used to express a lot of it for him.

It was his third year in grad school when The Nature of Prejudice was officially released, and Tom was in awe.

TOM PETTIGREW: I virtually committed it to memory. And so for my special exams, I requested to write on contact, and that’s where the four factors come from. 

Wait a second. I thought these were Allport’s four conditions.

TOM PETTIGREW: They aren’t in Allport’s chapter. They were what I deduced from the chapter in order to make it easier to study for the exam, and Allport accepted it, and I’ve used it, but that’s why the four factors got stuck in psychology textbooks.

Yeah, it’s true. If you look in Allport’s original chapter, you can definitely see where he talks about the importance of equal status, cooperation, etc., but at no point does he say: “Here are the four conditions for optimal intergroup contact!” That was Tom…and so I’m now referring to them as Pettigrew’s Four Conditions.

But over the years, he’s actually developed some mixed feelings about this contribution.

TOM PETTIGREW: People started then publishing papers all over the place saying, Hey, here’s another factor that’s required. Another factor. And before long, contact theory by the sixties was getting to be worthless because there were virtually no contact conditions in the whole world that would meet all of this laundry list of conditions.

Research on the contact hypothesis was spinning. It captured the attention of so many people, and everyone wanted a piece of it. But when you sit back and look at a giant pile of studies, how can you make sense of it? Does contact actually work? Are these special conditions really necessary?

One way to answer questions like this is to use a statistical tool called meta-analysis. It’s basically a way of combining the results of a bunch of different studies and summarizing them mathematically. It also lets you look at patterns that emerge—like does contact reduce prejudice more in studies that made sure people were equal status? You see where I’m going with this.

TOM PETTIGREW: So, contact made sense to me in terms of my own life, but I’d always wanted to do a meta-analysis on the studies, but there were two things holding me back. One, there weren’t that many studies for quite a while. And two, the way people summarize research was quite inadequate in the old days, by which I mean the sixties and seventies. It wasn’t until meta-analysis came along that I began to think, Ah, now we have a real way to summarize effects. Yeah. And now we’ve got enough studies to do it. So those two things had to come together for me, even though I’d been wanting to do it for 50 years. And then, oh, there’s another essential. You have to have somebody more compulsive than I am and who’s really good at it. And that was Linda. 

LINDA TROPP: Yeah, that that would be me. I was definitely the very detail-oriented, record keeping one of the pair of us.

That’s Linda Tropp. She’s a psychology professor at the University of Massachusetts Amherst, but she got her PhD in 2000 at UC Santa Cruz—where Tom Pettigrew was a professor…sort of. She had been wanting to work him as a grad student…

LINDA TROPP: …but Tom had officially retired in 1994 and I was like, oh, darn I’ll never get the chance to work with him. But I had a class with Tom, and I was a TA for Tom because he was still teaching some classes after his official retirement. And then at one point in my third year, it was the third floor landing in Social Sciences 2, by the elevators, if you remember this, Tom. You told me that you were planning to apply for a grant to support a med analysis of the contact literature. And then Tom asked me if it would be okay if he wrote me into the grant as the designated grad student to work with him on the project. And I was like, of course. I’d be honored. And so that was really, now upon reflection, I had no idea that that little conversation would have such an impact on the next 10 years of my life.

And so they began collecting study after study after study from the sixty years of research testing the contact hypothesis.

LINDA TROPP: We were estimating like, it’ll be like 150 studies, something like that. Right? Like we thought the project would last maybe a couple of years. And, little did I know that, I mean, it took us five and a half or six years just to create the dataset because we kept trying to get to the point where, you know, you look up studies from different people’s reference lists and you start coming across the exact same studies that we’ve kind of exhausted the literature, and we just kept not getting to that point. #

TOM PETTIGREW: Linda is quite right. I didn’t realize what a job it was going to really be. I’d never done– I’d done small analyses of 20 studies or something, but nothing like this. And it did go on and on. I think we, before we were through with gathered almost 900, of which 515 met our conditions, but my poor wife thought it would never end and it didn’t look like it was going to for a while.

LINDA TROPP: And then also I do remember where you had expressed at one point that we should have a meta-analysis that covers the whole century. And we had only gathered papers through December, 1999, which did not represent the whole century, and that we should therefore collect papers from December, 2000. Do you remember that?

TOM PETTIGREW: No, I had forgotten that. That was my compulsivity. I wanted to the end of the century. 

LINDA TROPP: Yes. We both had compulsivity that presented different ways.

TOM PETTIGREW: In different ways, yeah.

And when all was said and done, data from more than 250,000 people from 38 different countries collected over 60 years, showed that overall, having contact with people from different groups is reliably related to having less prejudice.[11]

And what about Allport’s—or Pettigrew’s—four conditions? Equal status, cooperation, common goals, and institutional support?

TOM PETTIGREW: …they turn out not to be essential after all. But they are facilitating. If you have them, you get a bigger effect. But you actually get at least small effects, positive effects, even when these conditions don’t hold. And one of the things that particularly interested me, and Linda has engaged in some of this research: In the most conflicted parts of the world—Cypress, South Africa, Pakistan, wherever—with all the conflict, you still get some effect, even though you could never argue that the four factors are operating. So, they do facilitate, but they’re not essential.

Yep. The more interaction we have with people who are different from us, the less prejudice we feel about them…even when none of the four factors apply. Sure, they help, but they’re not necessary.

The impact of this whole project can’t be overstated. The general view is that this was the thing that reinvigorated the contact hypothesis. In answering the question “Does contact work,” the psychologist Martin Hewstone wrote: “Thanks to the Herculean labours of Thomas Pettigrew and Linda Tropp…we can now answer with an emphatic ‘yes.’”

But where does that leave us?

LINDA TROPP: As I see it, at least one of the crucial things that I think our meta-analysis did was to help people or researchers in the field move beyond the basic question of does contact reduce prejudice or does contact improve intergroup attitudes? I think as I read a lot of the literature preceding our project, it was kind of like a ping pong match where people would be like, yes, contact works. No, it doesn’t. And it was just kind of one or the other. And I think having compiled the database and presented the findings that we do, it has allowed us as a discipline or even across disciplines to consider more interesting and perhaps more nuanced questions related to contact effect. So, you know, we kind of can set aside the basic question of “does contact reduce prejudice?” and say, “Well, for whom is contact most likely to reduce prejudice? What types of effects might contact have beyond just reducing prejudice? What about social change? What about policy support? What about many other types of outcomes?” So I think it’s helped us to really think more broadly and expansively about what contact can do and perhaps what contact cannot do.

Act II: Contemporary Experiments

So from a chapter in a book about prejudice in 1954 to today, the idea that contact with people who are different from you can minimize group hostilities has gained a lot of traction. Lots of studies have supported the idea. But one thing that can make these studies tricky is that a lot of them are correlational. You might have heard the saying: “correlation does not necessarily imply causation,” and that can be a real problem if we’re trying to build programs that will have an impact.

Here’s what I mean by that. Let’s look back at a study Gordon Allport did with his PhD student Bernard Kramer back in the 1940s.[12] That’s before he wrote The Nature of Prejudice. Back when you could publish an article in psychology that’s just titled “Some Roots of Prejudice.” They had asked a bunch of college students how often they associated with Jewish people, and the more these students—who were not Jewish themselves—said they had contact with Jewish people, the less anti-Semitic they were. Simple evidence for the contact hypothesis from 75 years ago.

So, sure one way to interpret that is that engaging in contact with Jewish people made these students less prejudiced. But exactly the same correlation could be revealing that it’s the students who were already less prejudiced who go out and have these diverse social experiences. It’s a bit of a chicken-and-the-egg conundrum. What came first? The contact or the lack of prejudice?

The way we deal with this in the social sciences is to run a randomized experiment. If we can get a big group of people and randomly give only some of them a contact experience, we can see whether that experience has a true influence on what comes next.

Unfortunately, we just don’t have a ton of studies like this. Just a few years ago, researchers went out and found all the studies they could that used a randomized experiment and looked at changes to prejudice at least a little while after the contact experience happened. They found just 27 experiments. The good news, though, is that if you meta-analyze those 27 experiments, you find that there’s reliable evidence that having a face-to-face interaction with someone from a different group does lead to less prejudice.[13]

Because I think these kinds of experiments are really compelling, I want to focus the second part of this podcast on two very recent examples of them. They’re from the last few years and highlight what contact could look like in the real world, around the globe…and what its limits might be.

First, we head to India…

Inter-Caste Contact

You’re probably familiar with the caste system in India. And maybe you’ve heard that it’s this old system of social class that has since been abolished. The reality is more complicated, as it usually is. And don’t let this podcast be your authoritative final word on caste dynamics, but a quick overview of things will set the stage…

Basically, a rigid hierarchical system for Hindu social groups goes back thousands of years, and is by and large based on one’s occupation. The highest status caste would include priests and teachers, and the lowest status caste would include street sweepers and people doing society’s “unclean” jobs. Historically, the caste system led to regional segregation, rules about who could share food, and strict traditions of who could marry who. This all reached its peak during British colonization as an easy way to enforce simple categories in the census. In fact, some historians claim that caste didn’t have nearly this significance before British rule.[14]

But in any case, following India’s independence, the 1950 constitution made caste-based discrimination illegal. Granted, though, there were still officially recognized castes, primarily to enact various affirmative action programs to help correct for historical inequalities. Just some terminology—we can distinguish between privileged caste and various disadvantaged castes, which are called “Scheduled Caste,” “Scheduled Tribes,” and “Other Backward Classes”

But anyhow, the point is that caste-based discrimination was made illegal. And just as the U.S. Civil Rights movement abolished all racism, so too must the caste system eradicated from India, right? Yeah, not quite.

In addition to plenty of anecdotal evidence, there are clear data showing caste-based discrimination in the modern era. For example, in 2005 researchers conducted a simple experiment out in the world.[15] They collected up hundreds of job advertisements from newspapers all over India. And they sent almost 5,000 fake resumes to those jobs. Now, these resumes were carefully designed so that they had identical educational qualifications and job experience. They were objectively strong applications. The only parts that really changed from one application to the next was the applicant’s name. In India, last names are closely tied to caste. You’d know someone’s caste as soon as you knew their name. So the researchers randomized the applications so that sometimes the person’s name denoted a high caste and sometimes a low caste.

Out of all of these resumes, only about 9% resulted in an invitation to interview for the job. Typical job search. But the question is whether the success rate differed depending on caste, and it did. If the name on the resume denoted a higher caste, the odds of getting an interview were 1.5 times the odds of getting an interview if it was a low caste name on basically the exact same resume. So whatever people might be saying about caste being a thing of the past, we can still see its influence.

SHREYA BHATTACHARYA: It’s surprising how high caste segregation is when it comes to urban areas even today.

That’s economist Shreya Bhattacharya, and she’s studied whether contact might help address caste-based prejudices in India. Because if there are these persistent stereotypes about caste and these groups remain fairly segregated, maybe bringing them together would be enough to chip away at the problem.

And, I guess I should say that Shreya eventually studied the contact hypothesis. It all started just because she was interested in these slum relocation programs happening in India. As of the 2011 census, 65 million people were living in slums throughout India[16]—that’s the whole population of France.[17]

SHREYA BHATTACHARYA: Slums are essentially like these, uh, sort of shanty settlements where people are living. And slums are pretty homogeneous in terms of caste composition. So there are clearly, you know, caste hierarchies at play, even there. That’s why you see the residential segregation by caste that you do see, because it operates even within slums.

For a variety of reasons, government programs have emerged that give free permanent housing to people living in slums. The Indian Government has even said it aims to provide almost 20 million houses for these purposes by 2022.[18]

Now, there’s plenty of debate about whether these programs are ultimately good or bad, but they allow us to study what happens when major changes are implemented in people’s lives. 

SHREYA BHATTACHARYA: Most people study slum relocation in Mumbai. And I heard of this relocation policy in Pune, and I said, oh my God, I know that city really well. Let me go and see what this is about.

By the way, Pune is a big city in India southeast of Mumbai. More than 3 million people live there—it’s one of the cities that Shreya grew up in.

So she went to check out this big slum relocation project and talked to people had been moved there. But even after doing some initial poking around, she couldn’t shake her interest in it.

SHREYA BHATTACHARYA: I started my PhD at the University of Houston, but every summer when I would be back in India, I would always just go back to see, oh, you know, what’s happened with the relocation? Are they still doing it? And you know, what’s the organization of people here? And, um, I think then I stumbled upon this really critical piece of information while communicating with the local government officials in Pune, which was, they showed me the list of people who were expected to actually move in in one of the next rounds of relocation.

And remember—caste is apparent in people’s names. So when Shreya was looking over the list, it sure looked like this slum relocation apartment was integrating different castes together. When she asked how they were deciding who to put in which apartment, they said…

SHREYA BHATTACHARYA: Oh, you know, we’re just seeing how far each slum is from the relocation site and accordingly just randomly, you know, deciding to put people in apartments. Our objective is to just fill up like the seven-story apartment and all the apartments there.

This is huge. This simple approach to filling apartments means that the government was basically running a randomized experiment on the contact hypothesis. It wasn’t that the people who were already more tolerant could opt into a more diverse community. Instead, their residential fate was essentially a coin flip.

By the way, it’s worth mentioning that this whole thing is reminiscent of some of the early research that got Gordon Allport thinking about the power of contact in the first place. A couple studies from the early 1950s looked at newly desegregated public housing apartments in the United States.[19][20] They found that feelings between White and Black people were more positive in the desegregated apartments. Would the same happen for caste more than 60 years later?

Shreya used official records to figure out the caste composition of each floor in this new apartment building. What proportion was privileged caste? What proportion was scheduled caste and scheduled tribes?[21]

SHREYA BHATTACHARYA: On a given floor, you’re going to find anywhere between 30% to 80% of people on the floor who are from a different caste than you.

And after people had time to settle in their new homes, she and her team surveyed the residents in more than 200 households.

In the end, she found that people who were randomly assigned to a floor with more neighbors of a different caste as them, the more open they were to other castes. There are a couple places in the survey where we can see that this is the case.

First, she asked people: How much do you trust members of another caste? And people who had been randomly assigned to live on a floor with more caste diversity eventually said they were more trusting of members of other castes.

But to get more to the heart of segregation, she asked about inter-caste marriage. As recently as 2005, less than 4 percent of all married women in the state where Pune is had married outside their own caste.[22] Less than 4 percent! And Shreya asked the relocation residents about this. Specifically, she asked how much they would support a law prohibiting inter-caste marriage and how much they would support an inter-caste marriage in their own family. The more caste diversity there was among their neighbors, the more cool people were with inter-caste marriage. And these effects of caste diversity got bigger the longer someone had lived in this new apartment.

This is all interesting, though, because it’s not clear that people actually made many close friends outside their own caste after moving to a diverse neighborhood.

SHREYA BHATTACHARYA: I think one of the ways this is working is through exposure, essentially. People would typically otherwise stay in very segregated neighborhoods where they’re only with people of their own type. And what’s suddenly happening is you don’t have a choice. Your slum is getting demolished, so you have to go and stay in this apartment.

So you don’t have a choice. Then you have to like mix with these neighbors or at least live in—Even if you don’t talk to anybody, you have a neighbor who you’re going to see up and down the corridor every day. So I think this has something to do with exposure. And I will not rule out that maybe in the beginning, there were more antagonistic attitudes in the beginning, because you’re suddenly staying with a whole bunch of people who you’ve never interacted with.

But I guess over time, seeing more and more of these people, more and more people who are not from your type and you realize that, you know, they’re not actually not that bad and they lead to being good citizens, good neighbors. I think it’s just the seeing them every day, and you realize that, you know, maybe your prejudices that you’ve been fed with are really not true.

Christian-Muslim Contact in Iraq

Okay, let’s look at another recent case of contact in action. Whereas Shreya’s study took advantage of a naturally occurring experiment with the governments’ slum relocation program, what if we wanted to deliberately create a contact experience? And you know, with caste in India, it’s something that people have already been trying to claim doesn’t matter anymore, so maybe people were ready to shed those prejudices. But what about intergroup tensions in the wake of a deep conflict that’s on everyone’s minds?

Maybe you see where I’m going with this. We’re going back to the conflict between Muslim and Christian people in Iraq. As a quick reminder, in 2014, ISIS took over huge swaths of land in Syria and Northern Iraq under a banner of ethnic cleansing of religious minorities, and Christian people—among others—were forcibly displaced, driven out of their homes for years.

Here’s political scientist Salma Mousa again.[23]

SALMA MOUSA: That kind of experience is obviously really traumatizing when you’re a few miles away from your home, but you know that there is an ISIS commander or fighter who’s living in your house, in your bed, who’s stolen all of your valuables. And you just hear word from your neighbors or people around of what’s left of your house. You don’t really know what’s going on. You come back three years later, you see everything, valuables gone. The deeds to your house are gone. It’s hard for you to prove ownership. Your AC is not even in the wall anymore. They’ve taken absolutely everything they could take. And this is obviously– this is a kind of experience that defines a community. This becomes your identity. Like, your identity become centered around this victimhood and this kind of experience of going through this kind of ethnic cleansing. And so we have a bunch of research about potential strategies to reduce prejudice and to improve intergroup relations. But for me, the real question is do these strategies work where it really, really counts? Like when the rubber hits the road and people can barely look each other in the eye, like, can these kinds of interventions to humanize the other, can that actually get us out of this and move towards some kind of social reconstruction?

The answer—maybe—was contact. An NGO in Iraq had reached out to Salma about surveying displaced Christians in IDP camps—IDP is “internally displaced people.” As they were doing these surveys, she started to wonder if there was anything more they could do—like actually do something in the community to see if it would help ease tensions between Christians and Muslims. She’d read about the contact hypothesis and wanted to see if that would work. The question was…what’s the right backdrop for studying contact in these environments?

SALMA MOUSA: We ran some focus groups in the camps and the number one suggestion that came out of that with soccer leagues, that was the thing people wanted to do. And actually, I had played around before with the idea of like drama and literature, literature courses, and art courses, and no one signed up. These are people in IDP camps with nothing to do. No one side signed up. And so that’s when we kind of went back to the drawing board and soccer became the obvious answer. And fortunately, it fulfills basically all of the criteria for contact according to the classic theory.

Those four classic criteria again are:

Equal Status – Everyone on the team has an important part to play.

Cooperation – Everyone on the team is working together.

Common Goals – Win the game!

Authority Support – Community leaders signed off on these activities.

SALMA MOUSA: So once we knew soccer was the way to go, we set up a series of new soccer leagues. So in total, we actually ran four leagues and the idea was that we would recruit pre-existing Christian teams. So the teams in this area generally are pretty ethnically homogenous, so we just sent an invite out to all the teams in the area and just said, we’re going to start up these new set of leagues and they’re going to be great. There’s going to be professional referees and new fields and bleachers, and people are going to watch and new uniforms, like it’s going to be very professionalized. But there’s like one big caveat, which is that to sign up, you agree that your team will have some players added.

And that’s the key. This wasn’t just a fun way to bring some lively soccer games to these communities, it was an experiment in contact.

All of the teams in these new soccer leagues were told that part of the goal was building community, so each team would be assigned three additional players. By random chance, these additional players would be three more Christians or they would be three Muslim players from nearby leagues.

Now, you might be thinking, why is it that we want to get Christians to love a group that ran them out of their homes? Let’s be super clear—it’s the extremist group ISIS that forced Christians to flee—not Muslims in general. In fact, the Muslim players in Salma’s soccer leagues—they had been displaced by ISIS, too. Nevertheless, the whole mess shook Christians’ feelings about Muslims in general. These were the rifts we’re hoping to mend.

SALMA MOUSA: I don’t bring together perpetrators and victims. That’s something I’m ethically not interested in.

But when she was getting permission from local priests to run the soccer leagues, they had the same reservations.

SALMA MOUSA: They were very skeptical, and I completely understood their skepticism. And it was mainly, why should we teach Christians to trust Muslims again, after what happened to us? Which I completely understand, obviously. And so that was, that made it even more clear to me that we had to target the intervention only to displaced people so we don’t get any of this victim-perpetrator thing going on.

And as you might expect, there were some growing pains. It took a change in norms for these mixed leagues to feel okay.

SALMA MOUSA: We had some players who we interviewed three or four months after the league ended, who said, before these leagues happened, you would never see a Christian team with a Muslim player. It just didn’t happen. And we did get some resistance. One of the teams was affiliated with kind of a, I wouldn’t go so far to say separatist, but definitely like a movement that’s for the independence of Syriac Christians in the area. And they were quite staunch in—they have a very strong sense of communal identity, and they were really hesitant. And that team actually happened to get randomized into the treatment group. And we obviously, we’re not going to force anyone. We just said, okay, this is the setup. Like, you agree to participate under these terms and we’re not forcing you. So it’s up to you just let us know what you decide. And a few weeks later, they came back and said, okay, well we’ll do it because they saw everyone else was doing it.

And it wasn’t just this one team that was hesitant at first.

SALMA MOUSA: At the beginning of the program, we saw a lot of reluctance to really welcome the Muslim players. The Christian players were not speaking Arabic, even though they’re fluent in Arabic because they kind of did not want the Muslim players to understand what’s going on. Even on the benches, they weren’t sitting next to each other. They were referring to these fields as ‘our fields.’ Why are you inviting the Muslims to the league, even? They’re going to ruin the league. They’re going to ruin our fields.

So, did the players change their tune? Did spending a couple months getting to know a few Muslim guys do anything to these Christians’ views? It seemed like it…

SALMA MOUSA: By the end of the program, one of the research staff was kind of joking with one of the players, because he was like, oh yeah, you’re going to invite them to the event, that’s great. And she’s like, what? I thought you, I thought Muslims suck and you know, they’re like, they’re the worst. And we shouldn’t, they’re ruining the league. And then the player was like, what are you saying? Don’t talk like that. We don’t talk like that here. So this norm against hate speech against Muslims, which was quite common that at the beginning of the program, it seemed to have really become taboo. Like, what are you talking about? We don’t talk about that here.

So it sure sounds like the tides might have been shifting, but this is just one anecdote. If we look across the league and consider the question scientifically, how do we know if this grand experiment actually made a difference? We can look at three key markers of success.

First, at the end of the season, players voted for a “best newcomer” award based on sportsmanship. They couldn’t vote for a player on their own team, but they had to vote for a player who joined the league as one of the additional players. Only 46% of the people on a Christian-only team voted for a Muslim player for this award. But the players who just by random chance had Muslim players join their team? 72% of them voted for a Muslim player for this award.

Second, when the league concluded, everyone was asked if they would volunteer to join a mixed team next season. Players who were randomly assigned Muslim teammates were significantly more likely to agree to play with Muslims again next season, compared to players on all-Christian teams.

And finally, Salma followed up with the players six months after the league ended to see who they were still training with. Only 15% of the players on all-Christian teams were training with Muslims. But of the Christian players on mixed teams, 64% were still training with Muslim buddies.

And there were other signs that contact was working in ways her surveys couldn’t quite pick up. For example, one of the soccer leagues was in a place that was a little harder for the Muslim players to get to.

SALMA MOUSA: …a neighborhood called Ankawa, which is a Christian neighborhood in the city of Erbil. And so the Muslims who we had brought in were coming from other parts of town. And so in that instance, that’s where you saw the Christian players on these mixed teams start to actually pool their money to cover the taxi fare of the Muslim teammates, which was quite touching, actually. Like, the average income of these places is not very high. And they went out of their way to make sure that those guys could come to practice and come to the games, which was really nice to see.

And even after the league had wrapped up, the friendships they’d formed held on.

SALMA MOUSA: Like we see the guys on mixed teams socializing months after the intervention. The Christians are like haggling with the security guards at a, like a bar to let their Muslim teammates come in, uh, to this Christian only bar so they can watch like the champions league final.

But here’s the thing. Even though playing on a mixed team actually succeeded in making Christians more tolerant of the Muslim players they met in the soccer league…

SALMA MOUSA: …it did not really, detectably anyway, change your behaviors or your attitudes toward Muslims in general. So this critical assumption of the contact hypothesis, that how you feel toward the people you meet is going to extend to the entire outgroup. I didn’t find evidence of that.

She had been looking for signs that her soccer players were starting to open up to Muslims in general—people they had never actually met before. For example, she was able to track whether they made a trip to Mosul, which was still a mostly Muslim city, and she organized a social event that was open to players, their families, and their friends, which meant Christian attendees would socialize not just with the Muslims they knew, but Muslim strangers as well. Across these off-the-field behaviors, the players on mixed teams were not reliably more likely to do these things.

So it’s true that one of the big hopes for contact is that the benefits generalize—meaning they go beyond the specific people you’re interacting with and reshape your views of the whole group itself. And there’s been some evidence that this actually does happen.[24] But not always. Like, go back to those super early contact studies during World War II where White soldiers came to like the Black soldiers they were fighting with. Even though this was encouraging news, these White soldiers didn’t actually end up becoming more open to Black people in general.[25]

Is this a critical blow to the contact hypothesis? Not necessarily. At least I don’t think so. The challenge is to get better at understanding when these experiences chip away at prejudice toward the whole group and when it doesn’t. From a practical perspective, I like how Salma frames the caution we should exercise…

SALMA MOUSA: At the very least, we can highlight that this generalization is not something you can assume is going to be true. And the higher the baseline prejudice, the more ingrained the conflict, the less likely it is that you’re going to get this generalization, because it’s just riskier to trust strangers for people who have been through some kind of personal trauma that importance of vetting people becomes even more important.

Act III: Limitations

Salma Mousa’s study on contact in Iraq naturally raises the question: are there limits to the benefits of contact? The fact that contact can—and likely will—result in less animosity seems extremely well established. But as we wrap things up, I want to shine a light on two critical issues.

The first thing to consider is whether the contact experiences we’re talking about are ultimately good ones. Listen, I’ve met a lot of people in my life—lots of contact—and I haven’t come away loving every one of them.

So although contact seems to reduce prejudice even when we don’t meet the canonical conditions for optimal contact, one thing seems to be actually critical—that it’s a generally good experience. 

Like, let’s imagine there’s a program trying to combat prejudices against gay and lesbian people and the program arranges for monthly meet ups between people with different sexual orientations. Now, assuming those meetings are at least somewhat pleasant—everyone’s kind and considerate,—this could very well chip away at any prejudices that might have existed.

But what if those meetups go poorly? What if one person is rude and the other is distant? One person feels ridiculed or even physically harmed? Well, the mere fact that there was contact has no magic properties—it was an unpleasant experience, and it might make prejudices just run deeper.

Here’s Linda Tropp again…

LINDA TROPP:  For any single contact experience we have, a negative contact experience will be more impactful on our attitudes than a positive one, which, you know, makes sense as human beings, we tend to be more vigilant in the face of threats, right? We don’t always remember all the positives in our lives. But overall, you know, all things being equal, what they tend to see is that people from different groups typically experience more positive contact than negative contact. So you still emerge with a net positive. So even though each individual contact experience that’s negative might be more impactful on your attitudes, overall, you tend to have more positive interactions than negative interactions with members of other groups. 

But what this also means is– kind of going back to the conflict context, right? If you have some severely negative examples that really stand out in your mind and contribute to kind of framing the narratives for intergroup relations that might help to explain why communities that used to be neighbors, you know, that co-existed pretty well that they might separate into factions, or there might be breakouts of violent conflict even after years of peaceful coexistence or relative integration, because those negative experiences are really impactful.

But let’s say we’re able to implement high-quality, positive contact experiences between people who are different from each other. Majority groups start to see minority groups more positively, minority groups start to see majority groups more positively. Problem solved. World changed. Right?

I mean, the question is whether this is actually what we want. Is getting everyone to like each other the ultimate goal? Political scientist Salma Mousa explains why focusing on reducing prejudice is one thing we can do, but it happens alongside other issues that pervade the societies we live in.

SALMA MOUSA: What we tend to call ‘intergroup conflict’ as scholars, a lot of times is very one-sided and there’s a structural oppression that’s happening of one group that’s the marginalized group. Part of that dynamic includes some individual-level things like prejudice, prejudice is an individual-level thing, but it interacts with these big structural inequalities. And so as scholars, there’s not that much we can do about the big structural inequalities, unfortunately. We can’t do much about war and residential segregation and inequalities in the legal system except draw attention to how they impact people’s lives. But maybe there’s something we can do about prejudice. These kinds of grassroots-level interventions might be one part of the puzzle. And that’s one part of the puzzle that, just from a pragmatic point of view, is one that we’re more likely to influence as just regular people or working with NGOs. And so that’s the one that I focused on in my study. And it’s one that I hope can can shed some light on the role of prejudice and post-conflict social reconstruction and other contexts outside of Iraq as well.

ANDY LUTTRELL: You know, the time course of a prejudice intervention also just seems more manageable to study. Like the class that I teach the most is psych of prejudice and discrimination. And you know, in the back of my head, there’s always this voice of like, yeah, but like, are the individual people really like the movers and shakers of these problems? But you go, but that’s what our tools let us understand, right? Our tools of social science and psychology specifically are like, I can understand what might make one person think one way or the other. It’s a whole other beast to figure out the mechanics of a system that– 

SALMA MOUSA: That’s the million-dollar question is how much do these individual-level interventions– how much does individual prejudice actually matter for shaping a conflict? That’s the million-dollar question. If we were to suddenly like snap our fingers and everyone in Iraq or everyone in Syria or everyone in the U.S. would be 100%, not just tolerant, but accepting and welcoming of all different faiths and races and ethnicities, would we still see this kind of horrible oppression that we see in those countries of certain marginalized groups? If the answer is yes, or if the answer is, yes, but you know, these attitudes are going to revert very quickly after whatever intervention you did is over, then it’s– For me, we have to ask ourselves a serious question of like, are these interventions are worth it?

This has been a major criticism of intergroup contact as a way to make social progress. Is getting everyone to like each other just a Band-Aid that distracts us from the deeper inequalities that will persist? In an influential article in 2010, psychologist John Dixon and his colleagues argued that positive contact between groups does help reduce prejudice, but it also leads members of marginalized groups to be less supportive of taking action to dismantle unjust systems. They’re more reluctant to protest for change and less attentive to remaining inequalities.[26]

Now, one reason not to let this totally undermine our faith in the contact hypothesis is that these effects pretty small—quite a bit smaller than the effects on reducing prejudice.[27]

But also, even if contact ends up reducing minority group’s interest in protesting social injustices, it actually makes the majority group more attentive to those inequities.

And we can see one example of this in Shreya Bhattacharya’s study of caste prejudice in India.

SHREYA BHATTACHARYA: And then the other interesting result was that there is an increasing knowledge of caste injustice, particularly among those from privileged castes because they realized that caste injustice has been increasing. And they also kind of anecdotally shared with me that initially they were opposed to affirmative action, but after seeing caste injustice play out the way it has, it really made them realize that there is an injustice that’s been happening historically. And affirmative action is a way that this is solved, and it’s not because the government is trying to play politics.

This isn’t the only place we see contact having this kind of effect. For example, positive interracial contact is associated with White Americans’ support for the Black Lives Matter movement.[28] Positive contact is related to straight allies’ involvement in LGBT issues.[29] And new research from Cyprus, Romania, and Israel shows that positive contact is associated with majority groups being more supportive of disadvantaged groups’ push for social change.

Granted, a lot of these studies have the same causality problem we talked about before—maybe it’s just the people who already support social change who are more open to having diverse social interactions. And we still haven’t seen that when push comes to shove, these folks put their money where their mouth is and actually take action against social injustice.

But the point is that when we’re thinking about interventions to create social progress, reducing prejudice might be one part of the equation, but we can’t lose sight of the bigger picture.


TOM PETTIGREW: More and more research has come from places all over the world. I never thought there be so much contact research in my life when I was writing about it initially.

I could have gone on and on researching this episode and cramming every last thing into it, but I think we’re pretty solid on the basics. To wrap up:

Despite the pessimism of the early 20th century, we now have a lot of evidence that meaningful social mixing—having individual contact with people who are different from us—can be a potent antidote for prejudice. In fact, we know that these experiences, whether on the soccer field or in our homes, can be the catalyst for changes in how we see other people.

Things like maintaining equal status and cooperation can boost the benefits of contact, but they’re not essential. As long as these experiences are reasonably pleasant, getting to know other people is generally a good thing. Granted, the benefits may not always run as deep as we’d like, and we should never lose sight of the systemic, institutional forces that also keep inequalities in place. But for chipping away at an individual’s own prejudices, contact sure seems to help.

Now, I’ve ignored a lot of work in the new wave of intergroup contact theory. For example, there’s now a ton of work on indirect contact—prejudices seem to also be lower if you have a friend of a friend who’s from a particular group, or if you are exposed to certain people on TV, or even if you just imagine interacting with someone from another group.[30][31]

TOM PETTIGREW: If in 1950, you would ask either Allport or me if these things would work, I think we would have said “no.” Regardless, I find these huge literatures have developed now on indirect contact to be really groundbreaking, things that we would not have thought possible just, you know, a half century ago.

Alrighty, that’ll do it for another episode of Opinion Science. This was a big one! Big, giant thank you to the experts who gave their time to talk with me for this episode, including Tom Pettigrew, Linda Tropp, Salma Mousa, and Shreya Bhattacharya.

There was a lot going on in this episode, so if you’re interested in the details, you can go to OpinionSciencePodcast.com to find a transcript of this episode that’s annotated as best I could with all the sources I drew on.

On that note, I’d like to plug a new book by Tom Pettigrew. Yeah, he’s still writing about these things after all these years. It’s amazing. His book is Contextual Social Psychology: Reanalyzing Prejudice, Voting, and Intergroup Contact. I drew on it a lot when putting this episode together, and it really is a great resource. You can find a link to the book in the show notes.

Also, check out the episode webpage for photos of the slum relocation apartment in India and the soccer leagues in Iraq.

Ok, is that it? I think that’s it. Please share Opinion Science with friends and colleagues, rate and review us online, subscribe on iTunes, follow on Spotify, whatever you do to keep up with podcasts, add this one to the mix.

But that’ll do it for now. I’ll see you back here in a couple weeks for more Opinion Science.

[1] https://apnews.com/article/middle-east-islamic-state-group-saddam-hussein-baghdad-iraq-296b5588995cf7be62b49619bf1a7bb6
[2] Pettigrew, T. F. (2002). Gordon Willard Allport: A tribute. Journal of Social Issues, 55(3), 415-428. https://doi.org/10.1111/0022-4537.00125 
[3] Dovidio, J. F., Glick, P., & Rudman, L. A. (2005). Reflecting on The Nature of Prejudice: Fifty years after Allport. In J. F. Dovidio, P. Glick, & L. A. Rudman (Eds.) On the nature of prejudice: Fifty years after Allport (pp. 1 – 15). https://doi.org/10.1002/9780470773963.ch1
[4] Report: The Power of Contact:  Designing, Facilitating and Evaluating Social Mixing Activities to Strengthen Migrant Integration and Social Cohesion Between Migrants and Local Communities (IOM UN Immigration)
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[7] Allport, G. W. (1954). The nature of prejudice. Addison-Wesley.
[8] Pettigrew, T. F. (2021). Contextual social psychology: Reanalyzing prejudice, voting, and intergroup contact.
[9] https://www.thecrimson.com/article/1964/4/9/thomas-f-pettigrew-pa-little-over/
[10] https://www.thirteen.org/programs/dynamics-of-desegregation/
[11] Pettigrew, T. F., & Tropp, L. R. (2006). A meta-analytic test of intergroup contact theory. Journal of Personality and Social Psychology, 90(5), 751–783. https://doi.org/10.1037/0022-3514.90.5.751
[12] Allport, G. W., & Kramer, B. M. (1946). Some roots of prejudice. The Journal of Psychology: Interdisciplinary and Applied, 22, 9–39. https://doi.org/10.1080/00223980.1946.9917293
[13] Paluck, E. L., Green, S. A., & Green, D. P. (2019). The contact hypothesis re-evaluated. Behavioral Public Policy, 3(2), 129-158.https://doi.org/10.1017/bpp.2018.25
[14] https://www.bbc.com/news/world-asia-india-48619734
[15] Thorat, S., & Attewell, P. (2007). The legacy of social exclusion: A correspondence study of job discrimination in India. Economic & Political Weekly, 42(41), 4141-4145. https://www.jstor.org/stable/40276548
[16] https://www.census2011.co.in/slums.php
[17] https://www.worldometers.info/world-population/population-by-country/
[18] https://www.trade.gov/market-intelligence/india-housing-all
[19] Deutsch, M., & Collins, M. E. (1951). Interracial housing; a psychological evaluation of a social experiment. University of Minnesota Press.
[20] Wilner, D. M., Walkley, R. P., & Cook, S. W. (1955). Human relations in interracial housing. University of Minnesota Press.
[21] Bhattacharya, S. (2021). Intergroup contact and its effects on discriminatory attitudes: Evidence from India. WIDER Working Paperhttps://doi.org/10.35188/UNU-WIDER/2021/980-8
[22] Goli, S., Singh, D., & Sekher, T. V. (2013). Exploring the myth of mixed marriages in India: Evidence from a nation-wide survey. Journal of Comparative Family Studies, 44(2), 193-206. https://doi.org/10.3138/jcfs.44.2.193
[23] Mousa, S. Building social cohesion between Christians and Muslims through soccer in Post-ISIS Iraq. Science369(6505), 866-870. http://doi.org/10.1126/science.abb3153
[24] Boin, J., Rupar, M., Graf, S., Neji, S., Spiegler, O., & Swart, H. (2021). The generalization of intergroup contact effects: Emerging research, policy relevance, and future directions. Journal of Social Issues, 77(1), 105-131. https://doi.org/10.1111/josi.12419
[25] Stouffer, S. A. et al. (1949). The American Soldier. Vol. 1, Adjustment During Army Life.  https://doi.org/10.1037/h0050766
[26] Dixon, J., Tropp, L. R., Durrheim, K., & Tredoux, C. (2010). “Let them eat harmony”: Prejudice-reduction strategies and attitudes of historically disadvantaged groups. Current Directions in Psychological Science, 19(2), 76-80. https://doi.org/10.1177/0963721410363366
[27] Reimer, N. K., & Sengupta, N. K. (2021). Meta-analysis of the ‘ironic’ effects of intergroup contact. https://doi.org/10.31234/osf.io/vrsqe
[28] Meleady, R., & Vermue, M. (2019). The effect of intergroup contact on solidarity-based collective action is mediated by reductions in SDO. Journal of Applied Social Psychology, 49(5), 307-318. https://doi.org/10.1111/jasp.12586
[29] Fingerhut, A. W. (2011). Straight allies: What predicts heterosexuals’ alliance with the LGBT community? Journal of Applied Social Psychology, 41(9), 2230-2248. https://doi.org/10.1111/j.1559-1816.2011.00807.x
[30] White, F. A., et al. (2021). Beyond direct contact: The theoretical and societal relevance of indirect contact for improving intergroup relations. Journal of Social Issues, 77(1), 132-153. https://doi.org/10.1111/josi.12400
[31] Zhou, S., Page-Gould, E., Aron, A., Moyer, A., & Hewstone, M. (2019). The extended contact hypothesis: A meta-analysis of 20 years of research. Personality and Social Psychology Review, 23(2), 132-160. https://doi.org/10.1177/1088868318762647 


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