Correlation Is Not Causation

Over the past couple of weeks, my two-year old son has made a strange and funny connection between two events. While I drive him back home from the daycare, he loves to eat crackers sitting in his car seat. It so happened that every time he finished eating his crackers, a BIG BUS drove past my car and this happened many times. Now he’s made the connection that – Eating Crackers = Seeing a BIG BUS. Yesterday he ate his first cracker and waited for a while and there was no bus. He asked for another cracker and even after eating that, there was no bus. Finally upon eating 4 crackers, he was thrilled to see the BIG BUS appear on the road. I am sure in his cute little brain he thinks that he can make his favorite BIG BUS appear by eating crackers.

Pattern recognition is deeply ingrained in our reptilian brain and to a large extent our survival and progress depends on making meaningful connections between two events. When clouds appear = run for shelter; Roaring of a Lion = hide / run for life, etc. However we’ve also known to make many incorrect connections. For ages it was believed that appearance of comet in sky meant famine, death of the king, wars and bloodshed; Black cats bring bad luck, etc. All our superstitions are also driven by our pattern recognition reptilian brain.

We blindly imply if two events occur together (Correlation), one causes another to occur (Causation) i.e. our default System 1 thinking assumes Correlation = Causation. I see this mistake being made every day by media, press, educated class and scientists. Lets see some popular beliefs.

  • Happy employees are more productive
  • Vaccination causes Autism
  • Diet soda causes obesity
  • Lice in bodies produce good health

I am sure the events mentioned above are strongly correlated i.e. they are observed at the same time. For any two events (say A and B) to be correlated, there are three broad possibilities. Here is a simple explanation from the book This Will Make You Smarter

“Imagine you’re watching at a railway station. More and more people arrive, until the platform is crowded, and then—hey, presto!—along comes a train. Did the people cause the train to arrive (A causes B)? Did the train cause the people to arrive (B causes A)? No, they both depended on a railway timetable (C caused both A and B)”

Lets revisit the above beliefs –

Happy employees (A) are more productive (B) –

  • A causes B – Happiness causes higher productivity (less likely)
  • B causes A – High performers naturally feel happy because they make more money and are treated special (likely)
  • C causes both A and B – Hiring right candidate for the right job causes both happy employees and higher productivity (most likely)

Vaccination causes Autism

There is no scientific evidence and is biologically implausible to believe vaccination causes Autism. Since Autism starts to appear at the same age children are vaccinated, this correlation is validly observed but wrongfully assumed as causation.

Diet soda causes obesity

It’s actually the opposite. Obese people prefer to keep calories low by drinking diet soda and not the other way around.

Lice in bodies produce good health

Sick people have high fever and lice cannot live in hot bodies and hence it’s not found in sick people.

Did you know ice cream is correlated to obesity; higher crime rates; increase in death by drowning and increase in forest fires? Check this video out.


ice cream was also believed to cause Polio and children were warned not to eat ice cream.


Here are some more funny correlations

With 99.79% confidence we notice – US spending on science, space and technology is correlated to suicides by hanging, strangulation and suffocation.



With 95.86% confidence we notice – Eating mozzarella cheese results in civil engineering doctorate awards



We are hardwired to make meaning out of patterns. There is a reason why superstitions still exist in the face of scientific facts. It is very hard for our reptilian human brains not to connect two events intuitively and make meaning out of it. We are tricked into believing anything through advertisements, political messages, religious sermons, etc. Awareness and education are the two most effective tools we have to become a ‘Rational Being’. So the next time you read some news or research article that says A causes B, you know how to think about it.


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