"Remember that time you went roller-skating with pink eyebrows? I was embarrassed even though it wasn't me, but because you're my mom." - My 7 year old


A prevalent and arguably universal human cognitive bias is the contagion heuristic - the idea that mere contact or association with a bad thing or person reflects badly on you. At a relatively young age, my daughter had picked up that others might judge her for her association with me. 

"A contagion heuristic is psychological heuristic which follows the law of contagion and the law of similarity."

But would these others be rational in doing so? 

In fact, the reason my eyebrows were pink were because my daughter had coloured them that way herself, the day before. We are also connected socially; they might consider her culpable for not noticing earlier and preventing me from leaving the house in such a state. (She ushered me to the bathroom on arriving at roller skating, but it was difficult to get it off without make-up remover.) 

But there are clearly times in which the contagion heuristic is wrong. The clearest examples come from inaccurate assessment of the contagiousness of a disease. Historically some people believed diseases like cancer were contagious. Cancer patients were treated badly or shunned accordingly. The same was true for HIV patients, where ignorance about transmission risk caused people to be afraid to shake their hands. (Princess Diana gained moral status for shaking hands with HIV patients; Boris Johnson lost some for doing the same with COVID-19 patients).

With diseases, science helps us get this right. But what about moral contagion? Is morality... contagious? Or at least, does associating with someone with poor morals signal you might also have poor morals?

"Moral contagion is a phenomenon in which individuals or objects take on the moral essence of the people who are associated with them." [1]

First, we can say what little evidence we have suggests that morality is at least in part contagious. This makes sense; morality is at least in part socially constructed, and moral messages do spread contagiously[2] and can have long term impact.[3]

But even if morality weren't contagious at all, the law of similarity still applies here. In the case of Jeffery Epstein, it was less that people associated with him were thought to have become sexual predators because of him, but rather that they too were engaging in such behaviour. Sexual predation itself doesn't have to be contagious, as long as social relationships between similar people are.

The MIT Media Lab had reasoned that contagion heuristic was wrong, and that instead they had a moral responsibility to take Epstein's money.[4] But the moral contagion did eventually spread to MIT, too, despite the fact they took precautions to hide the relationship.[4] 




  1. ^

    Liu J, Liao C, Lu J, Luo YJ, Cui F. Moral contagion: Devaluation effect of immorality on hypothetical judgments of economic value. Hum Brain Mapp. 2019 May;40(7):2076-2088. doi: 10.1002/hbm.24508. Epub 2019 Jan 9. PMID: 30624839; PMCID: PMC6865687.

  2. ^

    Brady, William J., and Jay J. Van Bavel. “Estimating the Effect Size of Moral Contagion in Online Networks: A Pre-registered Replication and Meta-analysis.” OSF Preprints, 7 Apr. 2021. https://osf.io/s4w2x/

  3. ^
  4. ^


New Comment
3 comments, sorted by Click to highlight new comments since: Today at 8:29 PM

How much of this effect is from morality being causally contagious (associating with Evil people turns you Evil) vs. morality being evidientarily contagious (Evil people are more likely to choose to associate with Evil people)?

I'd expect that, all else being equal, organisations secretly run in evil ways will be more willing to secretly accept money from other evil people, for many reasons including that they've got higher expectation of how normal that sort of behaviour is. It seems harder to imagine how a good organisation choosing to take dirty money would corrupt itself in the process if it was being reasonably diligent. Even if the moral contagion argument is wrong from inside hypothetical-good-MITs perspective, and so they should take the money, from everyone elses perspective it's still information we can update on.

If taking bad money for good causes is first-order good, because you're doing good things with it, but other donors can notice and it lowers their confidence in how good you are (since bad causes are more willing to take bad money), then you might lose other support sufficient to make it not worthwhile. There's probably some sort of signalling equilibria here, which is completely destroyed by the whole concept of accepting the money in secret. Hopefully actually good organisations wouldn't do that sort of deontology violation and would just make their donor lists public?

There could also be a self fulfilling aspect. In the knowledge that people have a moral contagion heuristic, deciding to disregard that (and associate yourself with the hypothetical immoral person) implies that you don't much care what other people think of your morals. Maybe because you don't have especially high standards.

I accidentally published this draft before finishing it and was surprised to see comments on it! I've decided to leave it as is, conclusion-less, as an exercise for the reader :).

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