Body-rocking and other habits of college students and persons with mental retardation.

Prevalence of body-rocking in college students was assessed, and the characteristics of body-rocking of college students were compared to those of individuals with mental retardation. For college students, the prevalence depended on the restrictiveness of the method used and varied between 3% and 25%. Video samples showed that when compared with college students, a greater proportion of people with mental retardation engage in body-rocking, seem less sensitive to situational factors, demonstrate atypical collateral behaviors, engage in less leg-kicking, and execute their body-rocking with larger amplitudes. There were no differences in duration or number of individual rocks or bouts of body-rocking. We conclude that body-rocking is a "normal" behavior whose form of expression may become atypical.