The idea that minds have immune systems once seemed metaphorical at best. Mounting evidence and novel arguments, though, suggest that the claim is quite literally true.1 In this essay, I’ll sketch the case for mental immune systems being real. I also mean to show that the emerging science of mental immunity – I call it “cognitive immunology” – holds great promise. In fact, it harbors real solutions to our world’s growing mis and disinformation problems.
Inoculation theorists have shown that the mind’s ﬁlters behave in a way that is strikingly reminiscent of biological immune systems: exposure to weakened forms of argument will tend to “inoculate” a mind against more formidable –and sometimes, more problematic– forms of inﬂuence.2 Hundreds of studies now attest to this phenomenon.3
We inoculate our bodies because it’s safer and more eﬀective to activate the body’s immune system before a deadly disease has taken hold. As the saying goes: an ounce of prevention is worth a pound of cure. The same principle holds for our minds: an ounce of mind-inoculation is worth a pound of cult deprogramming. Debunking the contents of a closed mind is always an expensive salvage operation; far better to employ “prebunking” to prevent infectious nonsense from taking hold in the ﬁrst place.4 For reasons like these, mind-inoculation techniques increasingly look like our best bet to stem the tide of digital disinformation.5
Healthy bodies post sentries at their gates. They scan for microbial threats and deploy a mobile army of “T-cells” and “B-cells” to ﬁght them oﬀ. In just the same way, minds post sentries at their gates.
They scan for information threats and deploy a mobile army of doubts and questions to ﬁght them oﬀ. Doubts and questions, it seems, are the antibodies of the mind.
You might say minds generate ”D-cells” and “Q-cells” when they feel threatened. Read an op-ed written by a misguided and pugnacious ideologue and observe how objections swarm in your mind. To all appearances, they attempt to neutralize the oﬀending information. Congratulations: you’ve just replicated an analogue of Elie Metchnikoﬀ’s Nobel Prize-winning discovery of phagocytosis,6 an experiment that laid the foundation for modern immunology! (Metchnikoﬀ inserted a citrus thorn into a starﬁsh larva and put them under a microscope; he then watched white blood cells swarm to the scene of the injury and begin consuming the citrus thorn.)
Simply put, the mind has an immune system of its own.
Evolution and the Brain
Thinkers versed in evolutionary biology can take a diﬀerent path to the same conclusion. The human animal is a “symbolic species”; for at least 70,000 years, our ancestors had to adapt to cultural environments riddled with problematic information—deceptive signals, malicious gossip, political spin, seductive superstitions, maladaptive myths, etc. Bad information could get you killed; in fact, bad ideas surely did kill oﬀ many would-be ancestors, leaving less-susceptible contemporaries free to become our ancestors. It seems our minds had to evolve defenses. In one form or another, mental immune systems have to exist.
Evolved systems have to defend themselves against internal and external threats. The body’s immune system is an evolved solution to this problem, but it is by no means unique. Evolutionary theory predicts that comparable systems will be found at many diﬀerent levels of selection.7 Look for such systems and you can ﬁnd them at work protecting cells, organs, and bodies, nations, cultures, ideologies, religions, and minds. These entities have “immune systems” too.
The mind’s immune system—its capacity to ward oﬀ problematic information—is implemented somehow in the brain. Neuroscientists have begun the work of understanding how. We know that the forebrain, the amygdala, and the parasympathetic nervous system are all part of the story. Daniel Kahnemann’s “System 2”–the brain’s machinery for slow, careful thinking–is also implicated.8
Trust and Suspicion
Suspicion seems to be natural selection’s way of calibrating minds to noisy and untrustworthy environments. Trust, by contrast, is natural selection’s way of calibrating minds to friendlier (less noisy) environments. These adaptive adjustments are conspicuous examples of mental immune function: the mind’s ceaseless eﬀort to strike the right balance between openness to useful information and resistance to harmful information.
The distinction between true and useful information is important, but I won’t emphasize it here: to a ﬁrst approximation, truths tend to be adaptive and falsehoods tend to be maladaptive.
The phenomenon of “identity-protective cognition” hints at an important truth—our minds can overreact to information it ﬁnds threatening.9 Conspiracy thinking, cynicism, and stubborn ideological rigidity can be understood as autoimmune disorders of the mind.10 On the other hand, mental immune systems can also be underactive, leaving people naive, credulous, and manipulable. A perfectly healthy mental immune system, it seems, would allow genuinely reliable information to shape beliefs, while preventing objectively problematic information from doing so. Assuming we want beliefs that are both true and useful, information that is either false or harmful would count as problematic. (This amounts to a “second approximation” take on what counts as problematic information: the idea is to keep reﬁning this deﬁnition. Epistemologists, evolutionary biologists, and cognitive immunologists are especially well-positioned to deepen our understanding here.)
The Science and its Applications
Epistemic perfection eludes us all: each and every one of us harbors myths and misconceptions. We can all beneﬁt, then, from “cognitive immunotherapies”: evidence-based interventions designed to boost and modulate mental immune response. (Imagine next-level critical thinking instruction based on a scientiﬁc understanding of how healthy minds wield questions to spot and ward oﬀ problematic information. Think: the “Socratic method” on steroids.)
As I see it, the question is not whether mental immune systems exist. The real questions include: How does the mind’s immune system work? Why does it fail? How can we make our mental defenses work better? What do those with “deep immunity” to problematic information do diﬀerently? Can it be taught? Can the science of mental immunity light the path to next-level critical thinking for all?
We can study mental immune systems the same way we study any natural system: scientiﬁcally. We can form hypotheses and perform experiments. We can build models, observe, and reﬁne our understanding. We can inquire into evolutionary origins and—just maybe—build a future where deep immunity to cognitive contagion prevents devastating outbreaks of unreason.
Inquiry into mental immune health raises dozens of fascinating questions. How robust is the analogy at its core?11 Can infectious information be parasitic? In what sense?12 Where do these analogies cease to be useful? What precautions must we take to avoid being misled?
What are the species of mental immune disorder? What disrupts mental immune systems? What “boosts” or strengthens them? Might a germ theory of cognitive contagion transform human prospects as radically as the original germ theory did? What would a mind vaccine look like?13
Immunologists hunt for “broadly neutralizing antibodies” (so-called BNAbs) knowing that their discovery can patch large gaps in the immune safety net; what if we devoted similar resources to discovering broadly neutralizing cognitive antibodies (BNCAbs)? Is Socratic questioning a BNCAb, as the Socratic Method’s long history of inoculating minds would suggest?14 What if we deployed such ﬁndings to improve education and address our misinformation problem at scale?
Are epistemic norms group-level cognitive immune adaptations? What can immunology teach us about the design of well-functioning speech norms? What can it teach us about the design of scientiﬁc institutions? Or the design of learning environments? What can it teach us about the design of well-functioning social media platforms?
I urge fellow researchers to help develop the science of mental immunity. I urge science journalists to tell cognitive immunology’s story and develop public understanding. And I urge leaders, policymakers, and problem-solvers in all domains to apply what we’re learning. Together, we can evolve a better world for all.
Read the entire “Mental Immunity” series:
01 The Science of Mental Immunity Has Arrived by Andy Norman
02 Cultural Immune Systems as Parts of Cultural Superorganisms by David Sloan Wilson
03 The Analogy of/and Inoculation Theory to Mental Immunity by Josh Compton and Sander van der Linden
04 Bad Ideas Recruit the Mind’s Immune System to Protect Themselves by Barry Mauer
05 Changing a Belief Means Changing How You Feel: The Role of Emotions in Cognitive Immunology by Steven P. Gilbert
06 Evolving My View on Mental Immunity by Ed Gibney
07 The Many Faces of Cognitive Immunology by Stephan Lewandowsky
3 Traberg, C. S., Roozenbeek, J., & van der Linden, S. (2022). Psychological Inoculation against Misinformation: Current Evidence and Future Directions, The Annals of the American Academy of Political and Social Science, 700(1), 136–151. https://doi.org/10.1177/00027162221087936 (link)
4 (2021). Countering Misinformation and Fake News Through Inoculation and Prebunking, European Review of Social Psychology, 32:2, 348-384, DOI: 10.1080/10463283.2021.1876983 (link)
5 Jon Roozenbeek, Sander van der Linden, Beth Goldberg, Steve Rathje and Stephan Lewandowsky (2022). Psychological inoculation improves resilience against misinformation on social media, Science Advances 8:34. DOI: 10.1126/sciadv.abo6254 (link)
7 It was David Sloan Wilson who helped me grasp this point. His contribution to this symposium elaborates the point.
9 Dan M. Kahan, Misconceptions, Misinformation, and the Logic of Identity-Protective Cognition, Cultural Cognition Project Working Paper Series No. 164, 2017, pp. 1-9. (pdf here)
11 Josh Compton, “Inoculation Theory,” in J.P. Dillard & L. Shen (eds.), The Sage Handbook of Persuasion: Developments in theory and practice, 2nd ed. (pp.220-236) Sage, 2013. DOI:10.4135/9781452218410.n14. (pdf here)
12 Maarten Boudry, Steije Hofhuis (2018). Parasites of the Mind: Why cultural theorists need the meme’s eye view, Cognitive Systems Research, Volume 52, Pages 155-167, https://doi.org/10.1016/j.cogsys.2018.06.010. (link)
13 I take on all these questions in Norman, A. Mental Immunity: Infectious Ideas, Mind-Parasites, and the Search for a Better Way to Think. (Harper Wave: 2021)
14 I construct a preliminary case for this conclusion in my book Mental Immunity: Infectious Ideas, Mind-Parasites, and the Search for a Better Way to Think. (Harper Wave: 2021)