When hundreds of Californians invaded the state capitol last week to demand the right not to vaccinate their kids, they were playing out a very modern conflict: science versus belief systems. Scientists tell parents that vaccinations are safe. But many parents prefer to trust their gut instinct that they’re not safe. This dialogue of the deaf is becoming the norm. Increasingly, people make their own decisions on health and diet, instead of outsourcing them to scientists, doctors or governments.

If you want to change people’s behaviour, don’t recite science at them, says Alan Dangour, nutritionist at the London School of Hygiene and Tropical Medicine (LSHTM). Rather, to nudge people to better decisions, we need to understand how they decide. Behavioural economics has identified cognitive biases that influence our decisions about money. Here are some biases and misjudgments that shape decisions on health and diet:

“‘Natural’ is good.”