In a classic experiment, psychology students were assigned to work either with “bright” rats or with “dull” rats, described as such by the experimenter. after a series of tests, the students' results showed that the “bright” rats had outperformed the “dull” rats. however, in fact, all the rats were of the same strain and breed; there were no preexisting differences between the groups. what caused the difference in their performance?

Recall that in one condition of the experiment conducted by stasser and titus (1985) about student council president candidates, all group members had access to the same information, and that in another condition, members had unique information that other group members didn't know. in the second (unshared information) condition, the group made a worse decision than in the first (shared information) condition. this occurred because groups seldom can agree on who is most expert. focus discussion on the information that all members know. often ignore dissenting opinions. avoid differences of opinion, given conformity pressures.