This is the editor's letter in the current issue of The Week magazine.

The human brain has two systems for assessing risk, and one isn't very reliable. The neocortex, which developed relatively late in human evolution, can make rational, risk-reward assessments based on evidence, data, and logic. The amygdala, a more primitive region we share with other mammals, reacts instantly to perceived threats with fear, anxiety, and the fight-or-flight response. Strong emotions often overrule logic, so our brains are biased to overreact to exotic risks like terrorism, plane crashes, and tarantulas, while downplaying the much greater likelihood we'll die of the flu, a car crash, heart disease — or COVID. For the past year, the pandemic has made us all subjects in a massive experiment on human risk assessment. We haven't done very well. Too many Americans decided that going about their usual activities without a mask or social distancing didn't feel as risky as the experts were saying ... and as a result, they caught and spread an invisible contagion. More than 560,000 have died.

Now our brains are assessing the risk of getting vaccinated vs. going unprotected against COVID. That task was complicated this week with the discovery that six women out of the 7 million people who received the Johnson & Johnson vaccine developed blood clots — a rate of 0.00008 percent. By way of perspective, an unvaccinated American's risk of dying of COVID is 1 in 1,666, and the risk COVID will cause severe illness and lasting, "long haul" symptoms is far greater. But the "pause" in J&J vaccinations, while ethical and responsible, will undoubtedly harden the resistance of the 30 percent who say they will not take any vaccine. That would be a terrible outcome — for them and for the rest of us. The pandemic won't truly subside until vaccinations give the coronavirus vanishingly few new people to infect. Those whose amygdalae are wrongly telling them vaccines are riskier than COVID may well determine when, and if, life returns to normal.