An abnormality of behavior characterized by one or more stereotyped and restricted patterns of behavior such as inflexible adherence to specific, nonfunctional routines or rituals, stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole-body movements), or persistent preoccupation with parts of objects. The behaviour does not serve an observable goal. In general the movements are not aimed at the environment, but at the person itself. Stereotypical behaviour is seen especially in children with sensory, intellectual and/or cognitive handicaps.