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Solving Public Health Challenges Using Behavioral Science.

Behavioral science principles explain why the biggest challenges in improving public health are still largely unsolved.
ImageNewristics Image02 March 2021

If something big happens, something just as big must’ve caused it - that’s what our intuition says. Humans tend to believe that major events result from major causes even though that’s rarely the case. In retrospect, that may make sense. But in fleeting moments, it’s hard to imagine catastrophic consequences from small insignificant causes.

This ‘Major-Event-Major-Cause’ heuristic, also called the Proportionality Bias, occurs when we instinctively conclude that the magnitude of the cause should match the magnitude of its effects. It also explains why we ascribe large conspiracies or motivated neglect to events that are objectively small in magnitude at the time of occurring but have large effects - like exposure to the coronavirus, sloppy use of a condom, or a typo in an official document.

How does Proportionality Bias play out?

  1. We believe large events must have had large causes. For example, a severe cold is caused by a powerful drug-resistant superbug.
  2. If the effects appear far larger than the accepted or logical cause, we try to balance the two. We use conspiracy theories or malice to explain away the cause as something bigger than it seems. That addition of intent or conspiracy to a cause makes a disproportionally smaller cause proportional to its effect. For example, a pandemic can’t be caused by accident; it must be a form of medical warfare.

The Representativeness Heuristic can also create this effect. With Representativeness Heuristic, people are inclined to believe that two things belong together because they superficially match each other.

Our intuition follows the notion that something big goes with something big while something small goes with something small. A reason for this matchmaking can be explained by the lesser mental processing needed to make sense of an event by equating the magnitude of a cause to the related effect. It over-simplifies a scenario to exclude complex intermediate steps that incrementally convert insignificant precursors into amplified consequences over numerous stages.

However, this linear approach between cause and effect is seldom true. For example, a high effort to use a pillow to break a wall will probably not affect when the wall breaks. Is it fair to blame that pillow for conspiring not to use its full power potential? Unlikely.

Such reasoning often occurs when we need to explain or justify big events. Patients may fail to acknowledge that exposure to a germ could leave them broken as a result of expensive medical treatments. Or a seemingly innocent walk in the park could expose them to a disease-causing germ. Even if it doesn’t make sense, a desperate patient might think the doctors are out to make money, and that their suffering is just a side effect of unnecessary medical treatments.

How can we counter Proportionality Bias?

  1. Hanlon’s Razor approach can help counter the negative effects of Major-Event-Major-Cause or Proportionality Bias. This approach states “Never attribute to malice that which is adequately explained by stupidity”. Taking Hanlon’s Razor approach can help deal with effects based on some human’s direct actions. You may substitute “stupidity” with a lack of awareness or low proficiency too. Using this approach can help us separate the emotionally heavy event from a cause that appears insignificant. Instead of balancing a weak cause with a strong effect by attributing it to malice, intentional neglect, or conspiracy to make the cause “heavier”, one can accept that the two don’t have to always be proportionate.
  2. It is also more helpful to focus on the effects without the cause and vice versa. We can attempt to understand the mechanisms involved in how small events can have disastrous effects. This creates the opportunity to let go of the proportionality bias and focus on other factors that could potentially amplify during a process, leading to a disproportionate cause-and-effect situation.


  • 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.
  • Spina, R. R., Ji, L.-J., Guo, T., Zhang, Z., Li, Y., & Fabrigar, L. (2010). Cultural Differences in the Representativeness Heuristic: Expecting a Correspondence in Magnitude Between Cause and Effect. Personality and Social Psychology Bulletin, 36(5), 583–597.