Résumé : Using a survey of a large group of first and final-year students of different disciplines, to study their belief in the existence of mutual benefits of voluntary transactions, we observe significant differences between economics and business students on the one hand, and students of other disciplines on the other hand. Those differences increase over time, due to economics students increasingly supporting that belief, and other students increasingly disagreeing with it. Beliefs of students specializing in the same topic also become more homogeneous over time. We therefore report evidence of both a selection and a learning effect of studying different disciplines.