In two experiments, it is shown that interviewers bias to a larger extent their questions towards their hypothesis when they interact with an interviewee than when they only prepare questions for a future interview. Also more biased questions are asked at the beginning of the interview than at the end. This does not seem to be due to the certainty entertained by the interviewers about their hypothesis. More likely, it appears that biased questions have an adaptative value and that they smooth the interview. All in all, our subjects were not especially concerned with diagnosticity.