PsychologicalDUAL-USE

Proportionality Bias

What it is

The intuition that big events must have big causes — so that a major outcome produced by a small, mundane, or accidental cause feels unexplained, and a conspiracy or grand design feels more plausible than the evidence warrants.

How it works

Leman and Cinnirella (2007) gave participants a fictional news report of an attempt on a president's life and varied only the outcome: the president died, survived, was wounded, or the shot missed. Readers who were told he died rated a conspiracy far more likely than readers given the identical facts with a lesser outcome. The bias is a heuristic about causal proportionality — usually large effects do have large causes — misapplied to a world where a single driver, virus, or mistake can change history. McCauley and Jacques (1979) had found the same pattern for presidential assassinations, and Douglas and colleagues place it among the core cognitive drivers of conspiracy belief. It supplies the feeling that Kennedy could not have been killed by one unimpressive man, that a pandemic could not have come from an ordinary market, that an election could not have been lost for ordinary reasons. Persuaders sell the proportional cause: conspiracy entrepreneurs supply a design equal to the disaster; partisans on both sides, after a shocking defeat, reach for stolen elections or foreign plots rather than mundane arithmetic; and, in the small register, a very upset person is assumed to have a very large grievance, which manipulators are happy to supply.

Real-world examples

  • •Leman and Cinnirella (2007): the same fictional account of a shooting was judged to involve a conspiracy far more often when the president died than when he survived, although nothing about the shooter or the evidence had changed.
  • •The assassination of John F. Kennedy by Lee Harvey Oswald in 1963 has been attributed to a conspiracy by majorities in polls for sixty years; the Warren Commission and later forensic reviews found a lone gunman, and the persistence of belief tracks the disproportion between the man and the event more than any evidence.
  • •Princess Diana's death in a 1997 Paris car crash — a drunk driver, high speed, no seatbelt — was investigated for three years by the Metropolitan Police's Operation Paget, which found no conspiracy; the mundane cause has never satisfied a substantial share of the public.
  • •After 2016, polling found large shares of Democrats believed Russia had altered vote tallies, a claim no investigation supported although Russian interference was real; after 2020, large shares of Republicans believed systematic fraud had decided the election, a claim rejected by more than sixty courts and the Justice Department. Each defeat felt too large for its ordinary causes.
  • •Both “engineered bioweapon” and “planned by pharmaceutical companies” narratives about COVID-19 supplied a cause proportionate to a global catastrophe; whether the virus emerged naturally or from a laboratory accident remains unresolved, but neither leading hypothesis involves the design the narratives require.
  • •A manipulator who wants a target to see a slight as a betrayal needs only to raise the emotional temperature; the target, feeling a large reaction, infers a large cause and accepts the one on offer.

Ethical guidelines

Where the line is

Investigating whether a large event had a large cause is legitimate inquiry; the line is crossed when a persuader offers the audience a cause proportionate to their shock in place of a cause supported by evidence, and profits from the fact that a small, mundane explanation feels like no explanation at all.

  • ●Size explanations to the evidence, not to the outcome; if the evidence supports a small cause for a large event, say so and resist the pressure to supply a larger one.
  • ●Do not build an audience by offering designs proportionate to disasters; it is a reliable business model precisely because it sells a feeling, not a finding.
  • ●When you present a real conspiracy — they exist — show the documents, the participants, and how it stayed hidden; the size of the outcome is not among the evidence.
  • ●After a defeat, resist supplying your side with a plot; the mundane explanation is usually the one that would let you win next time.

How to defend against it

  • ►Run the outcome-swap test: would you accept this explanation if the same events had produced a minor outcome? If not, the outcome is doing the persuading.
  • ►Recall the base rate of small causes for large effects — a single infected traveler, one loose bolt, one driver — and the base rate of large conspiracies staying secret, which is low.
  • ►Ask what evidence exists apart from the size of the event; “this is too big to be an accident” is a feeling, not a fact, and a persuader who offers nothing else has nothing else.
  • ►Notice your own emotional temperature: a large reaction in you does not imply a large cause in the world, and someone raising the temperature may be preparing to supply the cause.
  • ►When investigating a real institutional failure, work through the checklist of ordinary failures — incentives, incompetence, chance — before reaching for coordination; most disasters are chains of small things.

References

  1. Leman, P. J., & Cinnirella, M. (2007). A major event has a major cause: Evidence for the role of heuristics in reasoning about conspiracy theories. Social Psychological Review, 9(2), 18-28
    The presidential-shooting vignette study varying only the outcome.
  2. McCauley, C., & Jacques, S. (1979). The popularity of conspiracy theories of presidential assassination: A Bayesian analysis. Journal of Personality and Social Psychology, 37(5), 637-644 · link
    The earlier finding that a successful assassination is more readily attributed to conspiracy than a failed one.
  3. Douglas, K. M., Sutton, R. M., & Cichocka, A. (2017). The psychology of conspiracy theories. Current Directions in Psychological Science, 26(6), 538-542 · link
    The placement of proportionality among the epistemic drivers of conspiracy belief.
  4. van Prooijen, J.-W., & van Dijk, E. (2014). When consequence size predicts belief in conspiracy theories: The moderating role of perspective taking. Journal of Experimental Social Psychology, 55, 63-73
    Replication of the consequence-size effect and its moderation by perspective taking.
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