Z:gnu-www-ja-frank--2a418d-It may seem natural to wonder/en

It may seem natural to wonder whether the differences reflected in Figures 10 and 11 might stem in part from the fact that students chose their instructors rather than being randomly assigned. Perhaps the ideological reputations of the two professors were known in advance to many students, with the result that a disproportionate number of the least cynical students chose to take instructor B's course. Two observations, however, weigh heavily against this interpretation. First, the average values of the initial responses to the four questions were in fact virtually the same for both classes. And second, note that Figures 10 and 11 record not the level of cynicism but the change in that level between the beginning and end of the course. Figure 11 thus tells us that even if the students in Microeconomics A were more cynical to begin with, they became still more so during the course of the semester. This finding is consistent with the hypothesis that emphasis on the self-interest model tends to inhibit cooperation.