Origins and control of stereotyped movements.

A large number of retarded individuals exhibit repetitive and rhythmical movements of a highly stereotyped character. Common forms of these behaviors include body rocking, head nodding, hand waving, head banging and so on. Such behaviors are distinguished by their apparently maladaptive and excessive nature. The frequency of these bizarre responses in negatively correlated with measured intelligence. Stereotyped movements usually have their onsets early in the life of the individual and, in many cases, appear to have become functionally autonous. A variety of theories have been proposed to explain the onset and maintenance of stereotyped movements. None can be accepted to the exclusion of others and all have some empirical support. Problems of measurement are particularly difficult ones in this area. Of the various methods devised to suppress stereotyped movements, those based on principles of learning seem to be the most popular. However, generalization and durability of suppression effects generally have not been dealt with adequately. Much less attention has been paid to ecological analyses of the natural environments in which individuals exhibits stereotypies. A case can be made that our knowledge about the initiating conditions for these behaviors and subsequent effects on the natural environment is far less than perfect. A number of research directions are suggested.