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proportionality bias

The proportionality bias is a tendency to believe that causes are proportional to effects in magnitude. Extreme events with momentous consequences have extreme, momentous causes. Mundane events have mundane causes.

Many people find it unbelievable that Lee Harvey Oswald with his 23-year-old mail-order rifle in his perch 175 to 265 feet above the Kennedy motorcade in Dealy Plaza could fire three shots in 8 seconds and hit a moving JFK with two of the shots. Oswald was a disgruntled, oddball nobody. John F. Kennedy was President of the United States, arguably the most powerful man on earth. A grand conspiracy fits the crime; a minor disaffected citizen felling our president doesn't. At least that is what some who study conspiracy theories think. For example, Patrick Leman claims:

Almost every big event has a conspiracy theory attached to it....

So what kind of thought processes contribute to belief in conspiracy theories? A study I carried out in 2002 explored a way of thinking sometimes called "major event-major cause" reasoning. Essentially, people often assume that an event with substantial, significant or wide-ranging consequences is likely to have been caused by something substantial, significant or wide-ranging.

Leman begins his article by listing a few major events for which conspiracy theories abound:

Was Princess Diana the victim of drunk driving or a plot by the British royal family? Did Neil Armstrong really walk on the moon or just across a film set in Nevada? And who killed President John F. Kennedy - the Russians, the Cubans, the CIA, the mafia...aliens? Almost every big event has a conspiracy theory attached to it.

Aliens killed JFK? I'd never heard that one before, but then I'm not an avid follower of all things conspiratorial regarding our 35th president. I would agree that alien assassins is grander than Oswald acting on his own initiative, but I fail to see how the work of thousands of people from clerks to engineers to mechanics to test pilots to administrators is less grand than a few people in a movie studio faking a moon landing. At the very least, we must qualify the relationship between the proportionality bias and conspiracy theories to note that not all conspiracy theories involve this bias.

Another student of conspiracy theories, Rob Brotherton, writes:

....research suggests that we might be psychologically predisposed to see conspiracies behind events like the Kennedy assassination. This is because of an unconscious mental rule of thumb called the proportionality bias. When the outcome of an event is significant, proportionally significant causes seem more plausible. When consequences are modest, more modest attributions are made. Psychologists have demonstrated the bias using a variety of experimental scenarios, from reports of disease outbreaks and tornadoes to plane crashes and crimes. The findings are consistent: we tend to infer big causes for extreme events and small causes for insignificant events. 

Why then are there no conspiracy theories about the assassinations of Martin Luther King or Bobby Kennedy? Weren't the consequences grand enough in the eyes of the social scientists promoting the major event-major cause idea? And why would anyone think that a conspiracy behind 9/11 involving Saddam Hussein or George W. Bush and Dick Cheney is any grander than the Osama bin Laden and 19 Al-Qaeda terrorists plot?

On the other hand, there have been several experiments that have shown people are more prone to believe a conspiracy was behind the assassination attempt of a (fictitious) president when the assassination was successful than when it failed (Brotherton). Brotherton writes:

We are unconsciously biased towards seeking proportionally grand, intricate, complex, and significant causes for grand, intricate, complex, or significant events. Explanations which meet this rule-of-thumb may seem more plausible and appealing than explanations which defy the intuitive logic of the proportionality bias. In his research, Leman found that conspiracist explanations were more likely to be endorsed for the successful assassination of a President than an assassination attempt which failed. In the real world, conspiracy theories of J.F.K.’s assassination have become mainstream while conspiracy theories about the unsuccessful attempt on Regan’s [sic] life are few and far between. It’s easy to believe a lone, unknown, and possibly unbalanced individual can wound the most powerful person on the planet. But such an insignificant cause may seem insufficient when it comes to killing the most important person on the planet; a long-running, systematic, and nefarious conspiracy can begin to seem more plausible. The death of Princess Diana, the 9/11 attacks, Hurricane Katrina: these momentous and shocking events have all produced enduring conspiracy theories, while the Regans [sic] and Irenes have been forgotten.

There seems to be good evidence that the proportionality bias is real and that it sometimes manifests itself in conspiracy theories. In any case, there is a long history of a belief that might be seen as a prime example of this bias: the neo-Platonic belief that causes must have as much or more reality or being than their effects.

This idea--the causal adequacy principle--culminated with an argument for the existence of a perfect supreme being by Descartes. The argument seems simple, but it is packed with nearly two-thousand years of metaphysical baggage:

[S]ince I am a thinking thing, and have in me an idea of God, whatever finally the cause may be to which my nature is attributed, it must necessarily be admitted that the cause must equally be a thinking thing, and possess within it the idea of all the perfections that I attribute to the divine nature.

The argument makes no sense to those of us who do not think of ideas and minds as "beings" caused by something which must have at least as much reality as the idea and the mind do. Still, the argument is the epitome of the proportionality bias, on par with other arguments that the universe must have a cause equal to or greater than itself.

Finally, there is a rare bias that is the opposite of the proportionality bias. We might call it the disproportionality bias and it manifests itself in something called the global consciousness project. Dean Radin and Roger Nelson believe that grand events like the assassination of JFK or the death of Princess Diana cause blips on random number generators. This belief makes no sense to those of us who do not believe that there are immaterial minds that harmonize with each other at times and bring about an effect in the physical world noticeable only on machines that do nothing but generate more-or-less random numbers.

See also hidden persuaders (cognitive biases, fallacies, and illusions).

further reading

Brotherton, Rob. 2015. Suspicious Minds: Why We Believe Conspiracy Theories. Bloomsbury Sigma. Review in The New Yorker.

Carroll, Robert Todd. 2013. The Critical Thinker's Dictionary: Biases, Fallacies, and Illusions and what you can do about them.

LeBoeuf, R. A., & Norton, M. I. 2012. Consequence -cause matching: Looking to the consequences of events to infer their causes. Journal of Consumer Research, 39 (1), 128-141. Draft online.

blog and web articles

Psychology Postgraduate Affairs Group Quarterly Special Issue: The Psychology of Conspiracy Theories Issue 88 September 2013.

The President is Dead: Why Conspiracy Theories About the Death of JFK Endure and When the levees break: Hurricane conspiracy theorising by Rob Brotherton. The Psychology of Conspiracy Theories blog.

The lure of the conspiracy theory by Patrick Leman. 11 July 2007. NewScientist.com news service. "A study I carried out in 2002 explored a way of thinking sometimes called "major event - major cause" reasoning. Essentially, people often assume that an event with substantial, significant or wide-ranging consequences is likely to have been caused by something substantial, significant or wide-ranging."

Last updated 04-Jan-2016

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