The following is an excerpt of the intervention methodology. For more information, please see the full text of the article on the publisher's website or through your institution's library.

METHOD

SUBJECTS The subjects were 480 male and female college students drawn from introductory psychology courses at the University of Virginia. Mixedsex groups of 8 or 10 subjects were utilized. [...]

PROCEDURE

[...] The experimenter explained that for the first half of the study, subjects would be divided into two smaller groups to work on identical tasks. Each group would devise a solution.

Type of interaction. Following this introduction, the type of interaction between the two groups was manipulated. In the interdependent condition, subjects were informed that the two group solutions would be combined, and if this combined solution met a predetermined standard, every subject- would receive extracredit points. In the competitive condition, subjects were told that the two group solutions would be compared and only members of the group with the best solution would receive the extracredits points. [...]

Similarity of dress. The subjects were then randomly divided into two smaller groups and the similarity of dress variable was manipulated. Subjects were told that in lieu of normal business uniforms, everyone would wear a laboratory coat. In one-half of the sessions (Similar Dress), both groups of subjects wore white coats, while in the remaining sessions (Distinctive Dress), subjects in one group wore white coats and subjects in the other group wore red ones.

[...] In the first task subjects were given 15 minutes to devise a four-step rehabilitation plan for a young juvenile delinquent. [...] After the time period had elapsed, the group solutions were collected and the second task was explained. This time, the groups were to create a toothpaste advertising slogan. The slogan would be judged for originality. [...] Before proceeding to the second phase, subjects completed the first questionnaire which examined interpersonal attraction and perceptions of the two tasks. Following the collection of the questionnaire, the two groups were combined and the subjects were told that the remainder of the study involved one large group working together. The combined group would work on two more tasks and these tasks would have objective solutions. Consequently, the solutions would be judged immediately upon completion of the tasks. Once again, if the standard was met, everyone in the group would receive extracredit points.

Outcome of cooperation. For the first task, the group was to derive as many words as possible from the master word INDUSTRIAL. After the time period the experimenter manipulated the outcome variable. In Success condition, the-experimenter collected the words, compared them to a master list, and announced that the group had reached the criterion and that the subjects would receive some extracredit. In the Failure condition, the experimenter followed the same procedure but announced that the group had failed to reach the criterion and would not receive extracredit. For the second task, subjects read a brief summary concerning several truck drivers and were allowed 10 minutes to award a new truck to one driver and reallocate the remaining trucks. The experimenter examined the solution and announced a success or failure outcome identical to that subjects had received before. Subjects were then asked to complete a second questionnaire similar to the one they had been given after the first phase. [...]