Aronson, E., & Mills, J. (1959). The effect of severity of initiation on liking for a group. The Journal of Abnormal and Social Psychology, 59(2), 177-181.

“An experiment was conducted to test the hypothesis that persons who undergo an unpleasant initiation to become members of a group increase their liking for the group; that is, they find the group more attractive than do persons who become members without going through a severe initiation. This hypothesis was derived from Festinger’s theory of cognitive dissonance.” 3 conditions were employed: reading of “embarrassing material” before a group, mildly embarrassing material to be read, no reading. “The results clearly verified the hypothesis.”

http://dx.doi.org/10.1037/h0047195