PROBLEM
Abnormal repetitive movements, such aa body rocking, are frequently observed in the behavior of severely retarded individuals. Surveys'l. a ) have indicated that these stereotyped behaviors may be present in two-thirds of the institutional population included in the severely retarded range.
Several factors seem to be related to the rate of emission of these abnormal stereotyped motor activities. In general, environmental contexts that are boring, frustrating, or otherwise aversive are associated with increases in stereotypy, while those situations that introduce novelty, in one form or another, tend to produce a temporary decrease in stereotyped movements(*-There is also some evidence that body rocking can be brought under stimulus control, to some extent, by reinforcement proced~res'~ ).
The present studies attempted to determine whether the rate with which severely retarded persons engage in body rocking is infiuenced by variations in the social context. Informal observations by the authors had suggested that some patients display higher rates of rocking when they are in the same room with other rockers.
METHOD: STUDY I ' 0
Three replications, each involving repeated observations of four individual patients, were conducted. These replications employed the same basic design and differed only with respect to certain characteristics of the Ss.
Subjects. Twelve institutionalized retardates were included in the study. All had displayed rocking behavior on the ward, were ambulatory, and without a p parent gross sensory impairment.
Replication 1. Ss were 4 nonverbal severely retarded males with untestable