Why our brains cannot grasp viral spread

We are not wired to understand exponential growth - here's why

The speed of viral contagion of COVID-19 has been almost universally underestimated, even by the most reasonable, intelligent people. Why is this so?

It’s due to a hard-wired cognitive distortion – our brains are not designed to comprehend exponential growth.  Try this simple mind game, which illustrates the problem beautifully:

If you place one grain of rice on the first square of a chessboard, then double that number on the second square, and again double that number on the third square, and keep doubling like this until the 64th and last square on the board, how many grains of rice will be on that last square?

The answer is 9,223,372,036,854,775,808.  That’s nine quintillion and some change.

No way!, I hear you exclaim. That’s exactly my point.

The total number of rice grains on the board by the end is more than 18 quintillion.

In the case of the coronavirus COVID-19, current estimates are that on average each person infects 2.5 others.  That’s 1 grain of rice (you) on the first square, 2.5 on the next (your family members), 6.25 on the third (your friends), 15.63 on the fourth (their families)…and so on.

Though it doesn’t really work this way because there are behavioural, biological and geographical factors at play, maths says that unhindered COVID-19 could infect 76% of the population of the planet, or 5.8 billion people, by the 25th square on the chessboard.

It doesn’t bear thinking about.  Except we have to think about it, individually and as a community.

We must treat our universal dyscalculia like any other of the known cognitive biases – first, accept that we are miswired this way, and then consciously compensate for it in our behaviour. 

Viral contagion

Remember this in the COVID era.  Our brains cannot grasp exponential spread, or that our one small action could multiply into untold consequences.

It’s similar to the Domino Effect or the Butterfly Effect – the idea that the flap of a butterfly’s wings could in theory multiply into an impact on weather systems.

Don’t think too hard about it or layer it with needless anxiety.  Just accept it, then choose your behaviour consciously.  Through your everyday actions, endeavour to compensate for the almost guaranteed, dramatic underestimation of viral contagion.

So stay home, wash your hands and don’t touch your face.

And relax, love, move, breathe, get a little sun, hug your dog, think nurturing thoughts and eat healthy food.


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