Xenophobia, when associated with the anti-immigration sentiment, is not a pleasant word, but it was nonetheless crowned the Word of the Year by Dictionary.com in 2016. And Donald Trump should get some credit for it for denouncing Mexican immigrants: “They’re bringing drugs. They’re bringing crime. They’re rapists.”

Are immigrants really that bad? A fact check by Washington Post points to the contrary: Immigrants are less, not more, likely to commit crimes than native-born Americans. Thus, blaming immigrants for higher crime rates does not stand for much truth—even in this post-truth age.

Are immigrants bad for our economy? Study after study shows that immigrants, even illegal immigrants, help the American economy. An in-depth analysis by the National Academies of Sciences, Engineering, and Medicine demonstrates that “Immigration has an overall positive impact on long-run economic growth in the U.S.” In addition to posing little competition in wage or employment, “inflow of skilled immigrants suggests…positive wage effects for…native-born workers, and other benefits to the economy….” As such, the perception that immigrants bring an economic burden to America is false.

Case closed? No! Not only have the flames of the anti-immigration sentiment refused to die, but, on the contrary, they created a bonfire with energy enough to hurl Trump from a reality show star all the way to the White House. The economic rationale has utterly failed to make a case for the benefit of immigration. Why?

Many look to racism as the root cause for the current wave of the anti-immigration sentiment. Although there is some truth in it, racism can’t account for all of it for two obvious reasons.

First, although we are all somewhat biased, which is deeply seated in our evolved biological nature (check Harvard University’s Project Implicit to test your intrinsic bias), it’s unlikely that brazen racism on the fringe of our society could amount to so much as to get Trump elected. It’s doubtful that most Trump supporters cast their votes explicitly out of racial motives.

Second, statistics show that roughly a third of first-generation immigrants—including Hispanic, Chinese, Indian, and other Asian Americans—supported Trump, at least partly for his anti-immigration rhetoric. Clearly, racial discrimination fails to explain why these naturalized immigrants are against folks of their own stocks.

So, besides racial prejudice, what else is there behind xenophobia?

Among the evolved human instincts, we can find at least two for the anti-immigration sentiment: territoriality and the endowment effect.

Territoriality exists in a vast range of animals from insects to our close primate relatives. When resources (food, water, shelters, mates) are scarce, they become valuable. And the individual that owns a territory has the priority in exclusive use of these assets. That’s why butterflies monopolize a spot of sunlight under a tree, beavers fight off sneaky infiltrators into their home ponds, and chimps secure a tract of prime forest for their own use. We humans, likewise, protect a turf that could be our home or our nation.

So, territoriality, from an evolutionary standpoint, is about competing for and securing resources essential for our survival and reproduction. This explains much of our negativity against immigrants, who we may think covet or threaten our possessions and privileges, regardless of their ethnic backgrounds. (This is not to mention that many of our common social and economic resources—public schools, housing subsidies, welfare benefits—are supported by money from taxpayers. Our fairness instinct makes us vigilant against free-riders.)

Human territoriality also predicts the wax and wane of our anti-immigration sentiment. When the resources we own—jobs, wages, income stability, social benefits—are perceived vulnerable to immigrants, our anti-immigration sentiment perks up. This says much about the core of Trump supporters: undereducated, low-income workers, many of whom are in the declining and struggling manufacturing sector. They have the most to fear for losing jobs to immigrants.

Obviously, many cultural aspects of immigrants, such as languages, customs, and religions, have little to do with critical resources for the native-born, and territoriality can’t explain why we may still hold grudges about immigrants for these intangible, non-material things.

This vacuum can be filled with a phenomenon known as the endowment effect.

In a study published in 1989, economist Jack Knetsch experimented on some random people by giving them either a mug or a chocolate bar (about the same economic value). To his surprise, when asked a few minutes later whether they would keep the mug or the candy, a whopping 90% of his human guinea pigs clinched to whatever they had been given, instead of exchanging for something different, a blatant violation of the economic principle of free and equal exchange. Working with psychologist Daniel Kahneman and economist Richard Thaler, he calculated that if you want a mug from its owner, you have to double the mug’s price. If you are surprised by the big gap between the buying and selling prices in this case, you will be shocked by the discovery in behavioral economists Ziv Carmon and Dan Ariely’s study: you have to pay a ticket owner 14 times the ticket price to watch the final four of the NCAA basketball tournament. Even a greedy scalper may not ask for that much. The message for us is that ownership alone can generate a lot of subjective value.

Apparently, the endowment effect has a deep evolutionary root. Even chimps and capuchin monkeys also show this effect. For instance, psychologist Sarah Brosnan and her colleagues tried out an experiment with chimps in a way similar to Knetsch’s work with people. The researchers endowed the chimps with an ape version of mugs and candies: frozen fruit-juice sticks or PVC pipe filled with peanut butter. Chimps, indeed, were 15% or 20% more likely to stick to whatever they had already owned.

The endowment effect explains why we feel we own our society with the culture we are accustomed to, generically known as the American way of life. Such invisible “ownership” makes us inclined to reject other cultural values and practices—dresses, languages, rituals, religious practices—by claiming they are odd, unacceptable, or in conflict with our value system. In contrast, we tend to be more willing to accept people with similar cultural backgrounds. This explains why American society is so much more willing to accept European immigrants. Racial bias aside, the endowment effect also plays a major role.

Normally, economic benefits trump other considerations. That’s why James Carville’s 1992 artless motto—“It’s the economy, stupid!”—often works well in political campaigns. The endowment effect, however, muddies this simplistic approach to the immigration issue. It requires that new immigrants need to bring a considerably higher benefit to make those already here (native-born and naturalized citizens) happy to share the land and society.

In other words, if we see the right to make a living in America as something exclusive for American citizens, the right, according to the endowment effect, is expected to be worth a comparable amount (for instance, a 50% extra value, according to one estimate) for new immigrants. Obviously, there is no way for undocumented immigrants to contribute that much more than the citizens. That’s why they are unwanted for many Americans.

Clearly, territoriality and the endowment effect explain much for why immigrants are still unwelcome and why economic benefits brought by immigrants fail to put out the fire of the anti-immigration sentiment. Even so, it would be economically suicidal and socially tragic to set up policies based solely on our evolved instincts. Otherwise, the 53 Pilgrims could have been served with a massacre, instead of a feast, on the day we are still thankful back in 1621. Never mind about non-Anglo-Saxon immigrants—the Germans, Italians, Pols, Irish, Jews, Japanese, Chinese, and others—who have made it here and built our society to be, as many proudly call it, “the greatest nation in the world.”

Published On: February 1, 2017

Lixing Sun

Lixing Sun

Lixing Sun is currently a Professor of Biology at Central Washington University. He studies, teaches, and writes about animal behavior, human nature, evolution, and behavioral economics.


  • Liz Connor says:

    The main point in this article for me concerns ‘ownership’. There are many societies without a hard emphasis on ownership, and they are generally more accepting of immigrants. It’s more or less as John Lennon sang: ‘Imagine no possessions – I wonder if you can – no need for greed or hunger – a brotherhood of man’.

    So we have to let go of this idea of ‘private ownership/property’ in favour of ‘personal property’. Here’s the distinction:
    ‘Personal property includes “items intended for personal use” (e.g., clothes, homes, and vehicles, and sometimes money). It must be gained in a socially fair manner, and the owner has a distributive right to exclude others.’ [wikipedia]

    • Lixing Sun says:

      Thanks for your thoughtful comment! There is one study in an African tribal society where little endowment effect is reportedly shown. While it may simply due to some variation as to the strength of the endowment effect, I am more drawn to the question of whether there is a fundamental difference between personal property and communal property. Also, Owen Jones and Sarah Brosnan’s article, Law, Biology, and Property (chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://scholarship.law.wm.edu/cgi/viewcontent.cgi?article=1160&context=wmlr), shows us to the big picture as to the origin of private property in relation to the endowment effect. I think more exciting findings will ensue.

  • Paul J. Watson says:

    First and foremost, humans are informivores. So, all subcultures within metagroups (e.g., tribes and nations) have their status, and therefore the reproductive success of their individual members (their individual lifetime inclusive fitness), tied to developing, sequestering, and guarding precious subgroup-specific intellectual property, and other forms of strategic information. Newcomers, who have not adequately performed costly honest signals of commitment to a given subgroup, instinctually and institutionally will not be trusted with that subgroup’s intellectual property; they may steal it and spread it selfishly and non-strategically, from the point of view of the subgroup. Spread it outside the subgroup and even perhaps the host metagroup. Xenophobia, and perhaps most potently and importantly the strong penchant for manufacturing religious diversity within metagroups (wolverine clan, badger clan, etc.), and closely tying subgroup identities to those religious differences, may help to solve the enormous problem of protecting the “prime endowment” of subgroup-specific intellectual property. One of the most important functions of religions is to provide formulae and occasions for convincing honest signaling of commitment, so central to our pan-cultural human lifestyle of contractual reciprocity. This is a current research topic of mine — in a sense, religion as counter-espionage — our best way, traditionally, of protecting our most vital endowment. — Paul Watson

  • Rory Short says:

    As I understand it we are human beings and thus are able to contribute to general social well being. Certain attributes which might have served us during our evolution might no longer do so and as consequence we should not just automatically succumb to them. Trump is exploiting them rather than investigating them. He is a social dinosaur.

  • John Strate says:

    The endowment effect seems quite close to the economist’s notion of consumer surplus. According to prospect theory, people will engage in risky behavior when threatened with or experiencing losses. Xenophobia can spill over into violence. Perhaps immigrants add uncertainty to everyday social interactions (e.g., game of Prisoner’s dilemma) since the natives are uncertain at the intuitive level what strategy immigrants play (all D? all C? win stay; lose shift? tit-for-tat?) What are their norms? Can they be trusted? These fears likely decline over time as immigrants become assimilated and adopt the norms of the country they’ve moved to.

    • Lixing Sun says:

      Nice to put the endowment effect within the general framework of prospect theory. I agree that social norms do serve as a way of increasing predictability, which can favor the players involved. In this sense, I guess this is the rationale behind the evolution of norms. Further insights?

      • John Strate says:

        There’s the very old idea that human sociality (cooperativeness) evolved in the context of intergroup competition and conflict. We’re the war animal. I suppose xenophobia was a useful adaptation for most of human evolutionary history. Those from other tribes really did want to kill you and take your land, your water holes, your animals, and your women. Today? It’s not so useful when there’s need for cooperation on a global scale to deal with commons problems (e.g., global warming).

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