The cognitive processes we use in making diagnoses are characterised by heuristics and biases that are similar to those that underpin much human decision making.1 Although these processes are error prone, they have evolved as rapid and effective ways of making decisions in conditions of uncertainty and they are deeply ingrained in our psyche. Reducing such errors may be difficult and, indeed, some commentators are sceptical about whether such cognitive errors can be reduced at all.

Nevertheless, some strategies have been proposed to deal directly with cognitive errors, and these merit more consideration and field testing.2 These strategies involve what is sometimes …