Does studying economics discourage students' cooperative mind? Several surveys conducted in the United States have concluded that the answer is yes. The authors conducted a series of economic experiments and questionnaires to consider the question in Japan. The results of the prisoner's dilemma experiment and public goods questionnaires showed no differences between the behaviors of economics majors and nonmajors. The uniqueness of economics majors was found in their answers to questions concerning whether they behave honestly if they pick up money. The percentage of economics majors who said that they behave honestly was significantly lower than that of students in other disciplines. (Contains 4 tables and 1 figure.)