Why is it hard to believe that a major historical event could have a very simple cause? Why does the idea that a president could have been assassinated by a lone gunman seem less credible than that of a vast conspiracy orchestrated by hidden forces? Why do we believe that great disasters must necessarily have great causes?
This is what we call the proportionality bias.
1- What is proportionality bias?
The proportionality bias is a thought mechanism according to which an important, striking, or dramatic event must necessarily have an important, striking, or dramatic cause. Conversely, it intuitively feels difficult for us to accept that a major event could result from a trivial, ordinary, or insignificant cause.
“An event this huge can’t possibly be due to a simple accident, human error, or coincidence.”
So we look for (or invent) bigger, more complex, even mysterious causes. But in reality, the size of the cause does not need to be proportional to the size of the effect. Major events can result from absurd decisions, blunders, or very simple factors.
2- Why is this bias so common?
Because it responds to three major human needs:
– The need for meaning: Faced with a shocking event (such as an attack or a disaster), we seek a logical, coherent explanation, almost a “comforting” one. A trivial cause leaves us in the discomfort of the absurd or uncertainty.
– The rejection of randomness: We find it difficult to accept that great tragedies can happen without someone being responsible. This need to “find a culprit” often fuels conspiracy narratives.
– The dramatic effect: Stories with “epic,” secret, or extraordinary causes capture our attention more easily. Our brain prefers striking narratives over the banality of facts.
This bias plays a central role in how we interpret certain events, especially when they are tragic or spectacular. Here are some examples where this bias comes into play:
🕵️♂️ Famous assassinations
Take the example of the assassination of John F. Kennedy in 1963. According to the official investigation, a single man, Lee Harvey Oswald, killed the president. Many people find it hard to believe that one isolated individual could change the course of history on his own. This gap between the “smallness” of the cause and the “greatness” of the effect has fueled conspiracy theories for decades.
🦠 The COVID-19 pandemic
Another example: the COVID-19 pandemic. Some find it hard to accept that billions of lives were upended because of a virus originating in nature (or a laboratory accident). Faced with this difficult reality, theories flourish: a deliberately released virus, a plot by global elites, etc. The proportionality bias pushes us to look for a cause proportional to the global impact of the crisis.
🎥 Movies and stories
In fiction too, this bias is at work. We are used to seeing great catastrophes caused by powerful enemies, betrayals, or secret organizations. A breakdown caused by a simple oversight, a crisis triggered by an ordinary human mistake? Much less “satisfying” for our brain.
3- Why is this bias so powerful?
The proportionality bias is profoundly human. It responds to a need for logic, meaning, and justice: if something big happens, there must be a big cause. Otherwise, it’s absurd… and unsettling.
But this bias sometimes makes us incapable of accepting chance, complexity, or even human folly as explanatory factors. It distorts our judgment and can lead us toward mistaken or exaggerated interpretations.
4- Its effects in disinformation
This bias is often exploited by conspiratorial or sensationalist narratives. When a shocking event occurs, some malicious or misinformed actors will look for — or invent — a cause “big enough” for the event. This makes the theory seem more “logical” or more appealing than reality.
This is also why some simplistic media narratives can thrive: they offer an “big cause = big effect” explanation that avoids having to grapple with the complexity of reality.
5- How can you avoid the frequency illusion?
To avoid this bias, it is important to maintain a critical mindset and rely on objective data. For example, rather than relying on the feeling that certain things happen more often, it is better to check statistics and compare the actual frequencies of events. In addition, taking a step back from emotionally charged or sensational information can help avoid falling into this trap. Finally, being aware of the existence of this bias and its mechanisms can help us manage it better and avoid making decisions based on false impressions.
6- How can we combat this bias?
Accept that the world is complex, and that small events can sometimes trigger major consequences (butterfly effect, chaos, etc.).
Check the facts: a simple and “big” explanation is not necessarily the right one.
Beware of cognitive shortcuts that try at all costs to create symmetry between cause and effect.
Question “too perfect” narratives: a major catastrophe does not necessarily hide a grand conspiracy.
7- In summary (box)
The proportionality bias leads us to believe that big effects must have big causes.
It is deeply rooted in the way we think, as it helps us make sense of what surrounds us.
This bias can distort our understanding of the world, and it is often exploited in disinformation and conspiracy theories.
To stay well-informed, it is essential to recognize this bias and be cautious of it.
