The existence of emotion was judged in the experiments on the usual behaviouristic grounds, i.e. by the presence or absence of overt behaviour of the characteristic muscular variety. Naturally the behaviouristic position has also emphasized the motor mechanisms in dealing with emotion. The behaviourist seems to admit only that certain ways of behaving have previously been given names of emotions, for what he regards as descriptions of emotions are in fact descriptions of muscular behaviour. The idea of primary, or elementary emotions is a symptom of the usual scientific attempt to reduce whatever is dealt with, to its simplest terms. A knowledge of the primary emotions is principally important as a guide to the manner in which the compound and complex emotions are built up. The self-impulses of the organism, originating from automatic stimuli within its own genital system, combine with appropriate phasic motor impulses caused by environmental stimulation of the genital receptors.