A quote from Phil Zimbardo - an author of notorious
Stanford prison experiment - describing his colleague's undertaking:
"Imagine you are a college student who has volunteered for a study of group problem solving as part of a three-person team from your school. Your task is to help students from another college improve their group problem-solving performance by punishing their errors. That punishment takes the form of administering electric shocks that can be increased in severity over successive trials. After taking your names and those of the other team, the assistant leaves to tell the experimenter that the study can begin. There will be ten trials during each of which you can decide the shock level to administer to the other student group in the next room.
You don't realize that it is part of the experimental script, but you " accidentally" overhear the assistant complaining over the intercom to the experimenter that the other students "seem like animals. " You don't know it. but in two other conditions to which other students like you have been randomly assigned, the assistant describes the other students as "nice guys" or does not label them at all.
Do these simple labels have any effect? It doesn't seem so initially. On the first trial all the groups respond in the same way by administering low levels of shock, around level. But soon it begins to matter what each group has heard about these anonymous others. If you know nothing about them, you give a steady average of about a level 5. If you have come to think of them as "nice guys, " you treat them in a more humane fashion, giving them significantly less shock, about a level 3. However, imagining them as "animals" switches off any sense of compassion you might have for them, and when they commit errors, you begin to shock them with ever-increasing levels of intensity, significantly more than in the other conditions, as you steadily move up toward the high level 8 .
Think carefully for a moment about the psychological processes that a simple label has tripped off in your mind. You overheard a person, whom you do not know personally, tell some authority, whom you have never seen, that other college students like you seem like "animals. " That single descriptive term changes your mental construction of these others. lt distances you from images of friendly college kids who must be more similar to you than different. That new mental set has a powerful impact on your behavior."