[An ethological interpretation of stereotypy induced by environmental stimulus (author's transl)].

Stereotyped behavior in the schizophrenic patient is described, provoked by yawning or fragments of this act in the environment. It consists of elements that, in an ethological sense are reminiscent of activities which increase vigilance and cleanse the body. It is suggested that yawning brings about a certain 'mood transfer' which induces this kind of specific stereotyped behavior. The adequacy of an ethological interpretation of these symptoms of disease is briefly discussed.