The case of laughter is not quite so clear. It has, indeed, one characteristic which seems to favour the {42} view that the bodily resonance is everything, namely, that it is easily induced in a mechanical or quasi-mechanical manner. It is of all the expressive movements the one most subject to the force of imitation. Children’s laughter, and that excited by the popular game, the “laughing chorus,” clearly illustrate its contagious character.[26] Moreover, as we know, a fit of laughter may be brought on, in part at least, by actions which presumably reinstate some of the physiological elements in the process. Thus my son tells me that he was overtaken by an irresistible impulse to laugh when riding a horse without a saddle, and again when running a race; and my daughter had the same tendency at the end of her first mountain climb. It seems probable that the movements and the changed condition of the breathing function are prime causes of the irresistible tendency in such cases. It is, however, one thing to allow the indisputable fact that laughter can be excited in this seemingly mechanical way, another thing to claim for the reaction in such cases the value of the full joyous outburst. I believe that a person who watches his mental processes can observe that a merely imitative laughter does not bring the whole delightful psychosis which arises when some agreeable impression initiates the movements. To this it must be added that in the cases here touched on the imitation is not wholly mechanical. When we laugh because others laugh, do we not accept their laughter as a playful challenge and fall into the gay mood? And are we not, commonly at least, affected by others’ voluminous laughter as by a droll sight and sound, which directly stimulates the mirthful muscles? My son’s laughter, {43} in the circumstances just referred to, seemed to be directed to the movements of the horse’s ears, and to those of the boy running just in front of him. The movements of laughter have, in the case of some adults, come so completely under the initiative control of mental processes, that even when powerful organic forces prompt the movements, it is necessary to make a show of finding some cause of merriment.