There seems much, then, to be said for the hypothesis that all varieties of joyous laughter (when not reduced to a mechanical form) are excited by something in the nature of _a sudden accession of pleasurable consciousness_. Where the laugh is a new thing, unprepared for by a previous mood of hilarity, this rise of the spirits will, as we shall see later, probably involve a transition from a mental state which was relatively depressed. Where, on the other hand, a joyous mood prolongs itself, all that seems needed for re-exciting the movements of laughter (provided that the muscular {76} energies are equal to the explosion) is the sudden increase by an appreciable quantity of the pleasurable tone of the consciousness. We may further illustrate and verify this generalisation respecting the causes of joyous laughter by an examination of some of the more familiar circumstances in which this is wont to occur. Here we shall of course be dealing with the early and unsophisticated mind. Properly drilled “grown-ups” but rarely exhibit the phenomenon in its full intensity. (_a_) It is a matter of common observation that joyous laughter is a frequent concomitant of the play-attitude, especially at its first resumption. We have already found this illustrated in the laughter of “happy boys” just liberated from school. Here the conditions indicated, a relief from restraint and a sudden expansion of joyous activity, are patent to all. Closely related to this situation of released bodily energies is that of relieved mental restraint. During a nursery lesson—if only the teacher is a fond mother or other manageable person—the child is apt to try modes of escape from the irksomeness by diverting the talk, and especially by introducing “funny” topics; and the execution of the bold little manœuvre is frequently announced by a laugh. By such familiar infantile artifices the pressure is lightened for a moment, and the laugh announces a moment’s escape into the delicious world of fun and make-believe. The impulse to be gay and to laugh runs, moreover, through the enjoyment of play. No doubt this in its turn may often grow exceedingly serious, as when the illness of dolly, or the thrilling horrors of a bear’s cave, or of an attack by scalping Indians, are realistically lived out. Yet we must remember that this playful tampering with {77} the serious, even on its genuine side, is a part of the enjoyment. The momentary terror is desired by healthy young nerves, because the thrill of it, when the certainty of the nothingness lies securely within mental reach, is delicious excitement. A fuller examination of the relation of laughter to play belongs to a later stage of our inquiry.