Personal experience, prejudice and scientists’ judgements

The work of legal scholar Dan Kahan and social psychologists and other behavioural scientists that collaborate with him, and the research project around The Cultural Cognition Project at Yale University is a great source of insights about biases and their origins in cultural values that are difficult to reconcile. One of the examples given by Kahan is the use even by the best scientists of personal experience as a source of empirical evidence. Scientists should know that personal experience is incomplete and usually untimely, and cannot be used to make inferences. However, it is not uncommon (I can see it many days at my University) to hear scientists and scholars make statements from a very narrow sample of examples based on their personal experience. Sometimes this translates into absurd prejudices or statements based on national or professional stereotypes that one would imagine that had been eradicated from universities in the Middle Ages. The problem is that scientists are more affected by overconfidence than lay people. Therefore although scientists may be affected by biases less often than lay people, when they are affected they may be more overconfident about their biased judgements. Lay people are more aware of their limitations. That may explain perhaps why some of the best scientific minds have cooperated in the past with dictators and genocides. Kahan and his co-authors are therefore sceptical that isolated expert agencies can have the answer to many regulatory or policy problems, since they may run the risk of being biased in a way that makes correction of errors more difficult. There is no doubt that expert scientists have a role to play in policy, but there should be mechanisms in place to check their overconfidence, especially when they depart from their narrow fields of expertise.