Hugo Mercier

Jean Nicod Institute

Hugo Mercier is a cognitive scientist working at the Jean Nicod Institute in Paris. He studies human reasoning and communication, as well as cultural evolution. He is the co-author, with Dan Sperber, of The Enigma of Reason, and the author of Not Born Yesterday: The Science of Who we Trust and What we Believe.

Why do humans reason?

Reasoning is often seen as an essentially individual capacity: by examining the reasons behind our opinions, we should be able to refine them; by weighing up the pros and cons before making decisions, we should make better choices. However, experimental psychology and numerous historical and everyday observations show that this is far from always being the case. It even seems that reasoning is a particularly unsuitable tool for improving our opinions or decisions. Indeed, reasoning is biased: rather than being critical of our own opinions, it systematically seeks to defend them; rather than objectively evaluating a decision, it pushes us towards the decision that is easiest to justify, whether or not it is the best one. These results have led us to rethink the function of reasoning. Reasoning is thought to have a social function: it has evolved to enable us to defend our actions and opinions, and to evaluate the arguments and justifications offered to us by others. Seen from this angle, biases in reasoning appear to be adaptive traits. Thinking about the social functions of reasoning also draws attention to the contexts in which it works best: when we debate with peers in good faith.