The wrinkles about the eyes and mouth, which are perhaps the most expressive parts of the countenance, would not be so noticeable at first as the eyes, the lips, and the teeth, but they are always in the field of vision, and in time their special significance as a seat of expression comes to be noticed and studied. M. appeared to understand a smile sufficiently to be pleased by it about the end of the tenth month. The first unequivocal case of smiling in response to a smile was noticed on the twenty-sixth day of this month. Even at this age smiling is not imitative in the sense of being a voluntary repetition of the other’s action, but appears to be merely an involuntary expression of pleasure. Facial expression is one of the later things to be imitated, for the reason, apparently, that the little child cannot be aware of the expression of his own countenance as he can hear his own voice or see his own hands; and therefore does not so soon learn to control it and to make it a means of voluntary imitation. He learns this only when he comes to study his features in the looking-glass. This children do as early as the second year, when they may be observed experimenting before the mirror with all sorts of gestures and grimaces. The interpretation of a smile, or of any sort of facial expression, is apparently learned much as other things are. By constant study of the face from the first month the child comes, in time, to associate the wrinkles that form a smile with pleasant experiences—fondling, coaxing, offering of playthings or of the bottle, and so on. Thus the smile comes to be recognized as a harbinger of pleasure, and so is greeted with a smile. Its absence, on the other hand, is associated with inattention and indifference. Toward the end of the fifth month M., on one occasion, seemed to notice the change from a smile to a frown, and stopped smiling herself. However, a number of observations taken in the tenth month show that even then it was doubtful whether she could be made to smile merely by seeing someone else do it; and, as I say, the first unequivocal case was noticed toward the end of this month.