One of the least satisfactorily explored fields of psychology is that of motivation, and a major part of that field, social motivation, is perhapsthe least understood of all. An ever present component of motivation isemotion, acting as a source of internal stimulation. Consequently, Salzen'spaper, on the nature of social emotions, deals with a very importantphenomenon. His paper not only presents his TASS theory in detail, butincludes an extensive review of the literature on emotion from Darwin'spaper up to the present.