In a study on interpersonal attraction (Piercey and Piercey, 1972), 23 graduate psychology students, all from the same class, underwent 9 hours of sensitivity training in two groups. Students were given pre- and post-tests to rate their positive and negative attitudes toward each class member. Members of the same sensitivity training group rated each other higher in the post-test than they rated members of the other group in both the pre- and post-test, and members of their own group in the pre-test. The results indicated that the 9 hours of sensitivity training increased the exposure of students in the same group to each other, and thus they became more likeable to each other.