IMMIGRATION REFORM PROVED to be a particularly contentious issue in the US 2016 presidential election. In some respects, the attention appears justified by the continued relevance of immigration for American politics.¹ However, debate during the 2016 campaign centered on a set of policies, promoted by then-candidate Donald Trump, which had not previously been part of the national discussion. Perhaps the most notable of these was the proposal to construct a wall along the US border with Mexico.² The wall proposal drew both public support and incredulous criticism.³ Other proposals included mass deportation of illegal immigrants and a travel ban on Muslims.⁴ Most of Trump's campaign proposals are now official White House policy.⁵ Three surveys conducted by Pew Research between March 2016 and February 2017 indicate stable public support for the wall specifically, with approximately 35% of respondents endorsing it.⁶

Existing theories of immigration policy preferences often highlight the role of threat perception in explaining the divide between individuals who would prefer inclusive reform proposals (e.g., Path to Citizenship) and those who prefer exclusionary reforms (e.g., the border wall, large-scale deportation, travel bans, hiring restrictions).⁷ But these theories generally do a poor job of explaining the particular forms of exclusion that individuals support. That is, why build a wall instead of devoting more resources to Homeland Security or job protection measures? And why does such public support persist despite serious concerns of cost, feasibility, and efficacy?

To answer this question, it helps to realize that not all threats are alike. Existing theories tend to privilege certain types of danger (e.g., realism’s concern with the consequences of physical violence), or certain causal logics (e.g., maximization of material wealth).⁸ But humans are capable of discriminating between several different types of dangers and applying varied response strategies to mitigate each of them.⁹ The threats we deal with in our contemporary environment—immigration, hostile ideologies, climate change—are complex. It is quite possible that two individuals will see the same threat as posing different kinds of danger and will prefer different strategies by which to mitigate it.

I find in my research that some individuals see immigration as primarily a threat to the physical safety of Americans, while others see immigration as a threat to jobs, and yet others see immigrants as social pollutants, posing a threat to American values and culture. I apply a new theory of threat perception—Threat-Heuristic Theory—to test and explain the linkages between these different estimations of the threat posed by immigrants and individual-level variation in preferences for immigration reform. Using several survey experiments, I show that it is the contaminant concern—the perceived threat to values and culture—which uniquely predicts support for large-scale deportation and a border wall. 

Threat-Heuristic Theory

“Threat perception” refers to a subjective assessment that something in the world is likely to cause damage or be dangerous.¹⁰ So a “threat” can be whatever an individual believes has the potential to cause bad outcomes. For some, immigration rises to this level of concern; for others, it does not. The same variation can be observed for issues ranging from nuclear proliferation, to hostile ideologies, to climate change. And while we may disagree with one another’s assessment of a potential threat, the impulse to respond and mitigate threats in general is consistent with both observed behavior and our intuition.¹¹ This basic process of threat detection and response is species-typical—it takes place in human brains, both those of citizens and of policy-making elites.¹²

I draw on findings from biology and cognitive science to develop a theory that provides insights into how and why individuals differ in their preferences for dealing with some of the more complex potential dangers in the world. These other fields have demonstrated that our evolved threat detection systems and reflexive response strategies are in some sense organized around avoiding very specific bad outcomes.¹³ Three of these bad outcomes are especially relevant for political behavior: threats of physical harm, including death; threats of loss, both of material and non-material assets; and threats of contamination.

Threats are considered similar (and recruit the same cognitive systems) when they present the same potential bad outcome. For example, a threat of physical harm at the hands of another human recruits the same systems of threat detection and response in the brain and body as the threat posed by a deadly snake.¹⁴

The difficulty we face with contemporary threats—including immigration, global warming, and hostile ideologies—is that the “correct” classification of the potential bad outcome is not obvious. That is, while two people could agree that immigration poses a threat, they might well disagree on what kind. By measuring these threat assessments at the individual level, Threat-Heuristic Theory does not assume one concern is inherently more correct or valid. Rather, variation is expected.

Threat detection and assessment is only the first step in avoiding bad outcomes; appropriate response is the other.¹⁵ When humans are trying to avoid bad outcomes for large groups, response strategies are constrained. Threats of physical harm generate a small set of appropriate responses—physical protection and preventive aggression— where a vital contextual consideration is the inevitability of being attacked.¹⁶ Threats of loss lead to protective behavior not confined to physical barriers.¹⁷ Threats of contamination generate a preference for expulsion, isolation, self-monitoring, and even destruction of the contaminant.¹⁸

In the modern context, these response strategies may take the form of public policies. The theory expects variation in threat assessment to lead to variation in policy preferences for mitigating that threat. This individual-level variation can be observed on both large (electorate) and small (policy-making group) scales.

Empirical Evidence

In two large-N, online surveys of nationally diverse samples (Survey 1 N = 1,115; Survey 2 N = 985), I show that preferences for immigration reform policies are strongly correlated with specific threat assessments.  That is, when immigrants are perceived as posing a threat to American jobs and opportunities—regardless of their region of origin —individuals endorse hiring restrictions. Similarly, when immigrants are perceived as posing a threat to the physical safety of Americans—regardless of their region of origin— individuals endorse allocating more money to Homeland Security and policing resources to monitor those immigrants. But, in a forced-choice task, when individuals perceive “immigrants in general” to pose a threat to the values and culture of Americans (i.e., the social contaminant threat), they are substantially more likely to choose the option of large-scale deportation (expulsion) and a border wall (isolation) than enhanced Homeland Security measures, and considerably more likely to choose deportation/wall over immigrant hiring restrictions.

I also find that a relatively subtle prime of contamination heightens the salience of perceived values threats as predictors of policy preferences. This effect was observed for the endorsement of policies directed specifically at immigrants from Central America, but not at immigrants from the Middle East. The pollution narrative with respect to Latino immigrants to the United States is well-documented and this prime appears to interact with that narrative specifically.¹⁹ This finding suggests that both subtle primes and overt contaminant rhetoric might make values threats more salient.²⁰ Taken together with the finding that it is values threats specifically which affect support for large-scale deportation and border wall construction, such rhetoric may boost support for these policies over other options for immigration reform.

While it may be counterintuitive that a large physical barrier and disruptive deportation strategy are the preferred responses to an intangible sort of threat–social pollution–Threat-Heuristic Theory clarifies the link between threat perception and these policy preferences. Elsewhere, I apply the theory to preferences of American foreign policy-makers, showing that often the perception of contaminant threats is a factor in more drastic policies.²¹

Policy Implications & Conclusion

Threat-Heuristic Theory offers an explanation for the link between threat perception and policy preferences within a wide domain of potential dangers. The theory provides a framework within which to situate both well-interrogated threats (e.g., nuclear proliferation) and relatively new ones (e.g., climate change), without relying on a single, dominant causal logic to predict individual response preferences. Further, the theory explains why some policy preferences, which may strike observers as puzzling or infeasible, uniquely appeal to others who have classified the potential danger differently.

Finally, the quick, heuristic processing of threat assessment generates intuitive-feeling preferences, but the complexity of contemporary political threats also increases the probability that individuals will disagree on threat classification. This sets the stage for contentious debates because the dispute concerns the fundamental nature of the problem.  Hopefully, Threat-Heuristic Theory’s efforts to pinpoint the underlying sources of such disagreements will advance these discussions more productively in policy-making and public discourse.

1 John Tirman, Dream Chasers: Immigration and the American Backlash (Cambridge, M.A.: MIT Press, 2015). Daniel J. Tichenor, Dividing Lines: The Politics of Immigration Control in America (Princeton, N.J.: Princeton University Press, 2009).

2 Trump Campaign, “IMMIGRATION REFORM THAT WILL MAKE AMERICA GREAT AGAIN” (June 2015), available from https://assets.donaldjtrump.com/Immigration-Reform-Trump.pdf

3 Douglas Massey, “Donald Trump’s Mexican Border Wall Is a Moronic Idea,” Foreign Policy, August 18, 2015, available from http://foreignpolicy.com/2015/08/18/donald-trump-immigration-border/. Eugene Scott, “Poll: What Millennials Think About a Border Wall,” CNN, December 10, 2015, available from http://www.cnn.com/2015/12/10/politics/millennials-poll-harvard/index.html. Rob Suls, “Less Than Half the Public Views Border Wall as an Important Goal for U.S. Immigration Policy,” Pew Research Center, January 6, 2017, available from http://www.pewresearch.org/fact-tank/2017/01/06/less-than-half-the-public-views-border-wall-as-an-important-goal-for-u-s-immigration-policy/.

4 Trump Campaign, 2015; Associated Press, “How Donald Trump’s Plan to Ban Muslims Has Evolved,” Fortune, June 28, 2016, available from http://fortune.com/2016/06/28/donald-trump-muslim-ban/.

5 Kelsey Snell, Damian Paletta, and Ed O’Keefe, “Trump Wants to Add Wall Spending to Stopgap Budget Bill, Potentially Forcing Shutdown Showdown,” Washington Post, March 28, 2017, available from https://www.washingtonpost.com/powerpost/senate-republicans-show-resistance-to-trump-suggested-cuts-in-spending-measure/2017/03/28/ce3b97d0-13dc-11e7-ada0-1489b735b3a3_story.html.

6 Rob Suls, “Most Americans Continue to Oppose U.S. Border Wall, Doubt Mexico Would Pay for It,” Pew Research Center, February 24, 2017, available from http://www.pewresearch.org/fact-tank/2017/02/24/most-americans-continue-to-oppose-u-s-border-wall-doubt-mexico-would-pay-for-it/.

7 Paul M. Sniderman, Louk Hagendoorn, and Markus Prior, “Predisposing Factors and Situational Triggers: Exclusionary Reactions to Immigrant Minorities,” American Political Science Review 98 (2004): 35-49.  Jens Hainmueller and Daniel J. Hopkins, “The Hidden American Immigration Consensus: A Conjoint Analysis of Attitudes Toward Immigrants,” American Journal of Political Science 59 (2015), 529–48.  Anna Maria Mayda, “Who Is Against Immigration? A Cross-Country Investigation of Individual Attitudes Toward Immigrants,” Review of Economics and Statistics 88 (2006), 510–30.

8 For the emphasis of physical violence and extended analogies to bodily harm and death, see Thomas Hobbes, Leviathan, ed. Richard Tuck (New York, N.Y.: Cambridge University Press, 1996) and Kenneth N. Waltz, Theory of International Politics (Long Grove, I.L.: Waveland Press, 2010).  For the logic of greed as a driver of conflict onset, see Paul Collier and Anke Hoeffler, “Greed and Grievance in Civil War,” Oxford Economic Papers 56 (2004), 563-595.

9 Steven L. Neuberg, Douglas T. Kenrick, and Mark Schaller, “Human Threat Management Systems: Self-Protection and Disease Avoidance,” Neuroscience & Biobehavioral Reviews 35 (2011), 1042–51.

10 Angus Stevenson, Oxford Dictionary of English [Electronic Resource] (New York, N.Y.: Oxford University Press, 2010).  Note that in English, there is a second definition of “threat” which is a deliberate signal of the intention to inflict pain or take hostile action.  The literature related to this meaning is not relevant here.

11 Mark Schaller, Jason Faulkner, Justin H. Park, Steven L. Neuberg, and T. Douglas Kenrick, “Impressions of Danger Influence Impressions of People: An Evolutionary Perspective on Individual and Collective Cognition,” Journal of Cultural and Evolutionary Psychology 2 (2005): 231-47.  T. Butler, H. Pan, O. Tuescher, A. Engelien, M. Goldstein, J. Epstein, D. Weisholtz, et al., “Human Fear-Related Motor Neurocircuitry,” Neuroscience 150 (2007): 1–7.  Daniel Kahneman, “Maps of Bounded Rationality: Psychology for Behavioral Economics,” The American Economic Review 93 (2003), 1449-75.

12 Neuberg, Kenrick, and Schaller, “Human Threat Management Systems,” 143-147.  Leda Cosmides and John Tooby, “Neurocognitive Adaptations Designed for Social Exchange,” in The Handbook of Evolutionary Psychology, ed. David M. Buss (Hoboken, N.J.: John Wiley & Sons Inc.), 584–627. Arne Öhman, “The Role of the Amygdala in Human Fear: Automatic Detection of Threat,” Psychoneuroendocrinology 30 (2005), 953-58.

13 Mark Schaller, Justin H. Park, and Jason Faulkner, “Prehistoric Dangers and Contemporary Prejudices,” European Review of Social Psychology 14 (2003), 105–37. Daniel M. T. Fessler, “The Male Flash of Anger: Violent Response to Transgression as an Example of the Intersection of Evolved Psychology and Culture,” in Missing the Revolution: Darwinism for Social Scientists, ed. Jerome H. Barkow (New York, N.Y.: Oxford University Press, 2006), 101-17.  Michael E. McCullough, Robert Kurzban, and Benjamin A. Tabak, “Cognitive Systems for Revenge and Forgiveness,” Behavioral and Brain Sciences 36 (2013), 1–15

14 Vanessa LoBue, “Deconstructing the Snake: The Relative Roles of Perception, Cognition, and Emotion on Threat Detection.” Emotion 14 (2014), 701-711.  Arne Öhman, Katrina Carlsson, Daniel Lundqvist, and Martin Ingvar, “On the Unconscious Subcortical Origin of Human Fear,” Physiology & Behavior 92 (2007), 180-85.

15 Neuberg, Steven L., Douglas T. Kenrick, and Mark Schaller, “Evolutionary Social Psychology,” in Handbook of Social Psychology, ed. Susan T. Fiske, Daniel T. Gilbert, and Gardner Lindzey, 5th ed. (Hoboken, N.J.: John Wiley & Sons, Inc., 2010), 761–96. H. Allen Orr, “Fitness and Its Role in Evolutionary Genetics,” Nature Reviews Genetics 10 (2007), 531–39.

16 For a review, see Ralph Adolphs, “The Biology of Fear,” Current Biology 23 (2013), R79–R93

17 Fessler, “The Male Flash of Anger,” 106-109.  Paul Rozin, Laura Lowery, Sumio Imada, and Jonathan Haidt, “The CAD Triad Hypothesis: A Mapping Between Three Moral Emotions (Contempt, Anger, Disgust) and Three Moral Codes (Community, Autonomy, Divinity),” Journal of Personality and Social Psychology 76 (1999): 574-86

18 For a review, see Megan Oaten, Richard J. Stevenson, and Trevor I. Case, “Disgust as a Disease-Avoidance Mechanism,” Psychological Bulletin 135 (2009), 303-21.  For the power differential argument, see Neuberg, Kenrick, and Schaller, “Human Threat Management Systems,” 1048.

19 Kent A. Ono and John M. Sloop, Shifting Borders: Rhetoric, Immigration, and California’s Proposition 187 (Philadelphia, P.A.: Temple University Press, 2002).  J. David Cisneros, “Contaminated Communities: The Metaphor of ‘Immigrant as Pollutant’ in Media Representations of Immigration,” Rhetoric & Public Affairs 11 (2009), 569-601.  Dorothy Nelkin and Mark Michaels, “Biological Categories and Border Controls: The Revival of Eugenics in Anti-Immigration Rhetoric,” International Journal of Sociology and Social Policy 18 (1998), 35-63.

20 Hunter Walker, “Donald Trump Just Released an Epic Statement Raging Against Mexican Immigrants and ’Disease’,” Business Insider July 6, 2015, available from http://www.businessinsider.com/donald-trumps-epic-statement.

21 Marika Landau-Wells, “Bringing the First Image Back In: An Exposition of Threat-Heuristic Theory” (paper presented at the Junior Scholar Symposium, International Studies Association Annual Meeting, Baltimore, Maryland, February 22-25, 2017).