A spate of studies has shown that people who are susceptible to the exponential growth bias are less concerned about Covid-19’s spread, and less likely to endorse measures like social distancing, hand washing or mask wearing. In other words, this simple mathematical error could be costing lives – meaning that the correction of the bias should be a priority as we attempt to flatten curves and avoid second waves of the pandemic around the world.
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Surprisingly, a higher level of education does not prevent people from making these errors. Even mathematically trained science students can be vulnerable, says Daniela Sele, who researchs economic decision making at the Swiss Federal Institute of Technology in Zurich. “It does help somewhat, but it doesn’t preclude the bias,” she says.
This may be because they are relying on their intuition rather than deliberative thinking, so that even if they have learned about things like compound interest, they forget to apply them. To make matters worse, most people will confidently report understanding exponential growth but then still fall for the bias when asked to estimate things like compound interest.
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According to various epidemiological studies, without intervention the number of new Covid-19 cases doubles every three to four days, which was the reason that so many scientists advised rapid lockdowns to prevent the pandemic from spiralling out of control.
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The researchers speculate that some of the graphical representations found in the media may have been counter-productive. It’s common for the number of infections to be presented on a “logarithmic scale”, in which the figures on the y-axis increase by a power of 10 (so the gap between 1 and 10 is the same as the gap between 10 and 100, or 100 and 1000).
While this makes it easier to plot different regions with low and high growth rates, it means that exponential growth looks more linear than it really is, which could reinforce the exponential growth bias. “To expect people to use the logarithmic scale to extrapolate the growth path of a disease is to demand a very high level of cognitive ability,” the authors told me in an email. In their view, simple numerical tables may actually be more powerful.
Best in Moderation
Article URL : https://www.bbc.com/future/article/20200812-exponential-growth-bias-the-numerical-error-behind-covid-19