In October 1983 Daniel Kahneman and his friend and collaborator Amos Tversky published a paper in the Psychological Review describing what came to be known as The Linda Problem. Linda is a bank teller. She is young, clever, and forthright with her opinions, and was passionate about social justice in her student days. Participants in a study were asked which is more likely: 1. Linda is a bank teller; or 2. Linda is a feminist bank teller. 85 per cent of students at Stanford’s Graduate School of Business said the second was more likely. Of course, it is not. All feminist bank tellers are bank tellers; adding a caveat merely lowers the probability. Kahneman and Tversky argued that most respondents – and, by extension, people generally – are swayed by an instinctive, uncritical response because of biases in their thinking. These biases do not primarily show that our thinking is flawed (though it often is); rather, that we think in two main ways – fast and slow.

Three decades on from Linda’s invention, behavioural economics and evolutionary psychology have become major forces in cultural and political discussion. The British government has set up a unit to examine the merits of policies through this prism. Books with memorable titles referring to nudges, influence, tipping points, blank slates, and