How far the provocative of laughter mentioned by Darwin, namely, suddenly uncovering the child’s head (or his own) implied a rudiment of fun, I am not sure. It shows, however, the early connection between laughter and agreeable surprise, that is to say, a mild shock, which, though it borders on the alarming, is on the whole gladdening. One other early form of laughter, which is found also in certain young animals, is that excited by tickling. This has been first observed, in the case of the child, in the second or the third month. Preyer’s boy laughed in response to tickling in the second month.[106] Dr. Leonard Hill tells me that his little girl, who was by-the-bye specially sensitive to titillation, responded first by laughter in the tenth week. Since our analysis has led us to regard the effect of tickling as largely mental, and as involving a playful attitude, this fact confirms the conclusion that the specialised laughter which is the accompaniment of play occurs in a well-defined form within the first three months. To sum up: We find, within the first two or three months, both the smile and the laugh as expressions of pleasure, including sensations of bodily comfort and gladdening sense-presentations. We find, further, in the reflex reaction of laughter under tickling, which is observable about the {170} end of the second month, the germ of a sense of fun, or of mirthful play; and this is indicated too in the laughter excited by little pinches on the cheek at the end of the third month. It is certain that these tendencies are not learned by imitation. This is proved by the fact, established by Preyer, that imitative movements do not occur in the normal child till considerably later, and by the fact that the child, Laura Bridgman, who was shut out by her blindness and deafness from the lead of companions, developed these expressions. We must conclude, then, that they are inherited tendencies. Here the psychologist might well stop in his inquiries, if Darwin and others had not opened up the larger vista of the evolution of the species. Can we, by carrying the eye along this vista, conjecture how these instinctive movements came to be acquired in the course of animal evolution?