‘Probabilities Mess With Our Heads’

Conventional wisdom tells us that people are terrible with numbers. But as Kent realized back in the 1950s, we are even worse with words. In one study that Fischhoff co-authored, people had trouble understanding a 30-percent chance of rain. It wasn’t the probability that tripped them up, but the word: rain. Are we talking drizzle or downpour? All day or just part of the day? And over what area, exactly? (Communicating forecasts in Italian is extra challenging. In English, we can use forecast instead of prediction to convey uncertainty. In Italian, there is only previsione, which has a strong deterministic connotation.)

The divine cruelty of what happened in L’Aquila is that when Boschi said that a major earthquake was “improbable,” he was — and remains — correct. But where a career scientist hears the word improbable and knows that rare events do occur, a non-scientist hears improbable as shorthand for ain’t gonna happen.

Yet even the most carefully crafted communication from the Serious Risks Commission would likely have fallen short. Not because it would have failed to reach people or been met with suspicion, but because probabilities mess with our heads.

— At Matter, David Wolman reports on the story of seven Italian scientists who were convicted of manslaughter following a catastrophic earthquake that killed 297 people. The scientists were part of a “Serious Risks Commission” that concluded that a major quake in the near term was unlikely. Scientists across the globe are worried about the effect this case will have on experts who are asked to provide an opinion.

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Photo: Alessandro Giangiulio