How to consult an expert? Opinion versus evidence

In this article, two modes of non-binding communication between an expert and a decision-maker are compared. They are distinguished mainly by the nature of the information transmitted by the expert. In the first one, the expert reports only his opinion (soft information) concerning the desirability of a certain action, whereas in the second one, he is consulted to provide evidence (hard information) to convince the decision-maker. The expert’s ability to provide evidence increases with the precision of his information. The article shows that requiring evidence is always beneficial to the decision-maker whereas it is beneficial to the expert, if and only if the preferences of both agents are different enough.