At first sight we might be disposed to think that the feeling of sudden joy at the back of a merry explosion would prove to be an exception to this law. Since an element of novelty, a sense of joyous mental collapse under a sudden, yet harmless stimulus, runs through all our laughter, there might seem to be no room for any increase of depth and volume. But this is not so. A child’s feeling of the “fun of it” at the approach of the tickling hand seems to gain in volume and force with the repetition of the experience. The zest of the enjoyment of a laughing romp with the nurse, or, better, with the father, of watching the funny ways of a kitten, and so forth, grows fuller because of the increasing complication of the psychosis behind the laughter.[123] (_b_) In the second place the development of an emotion is essentially a differentiation of it, not merely into a more definite kind of experience as a whole, but into a number of {191} distinguishable sub-varieties of feeling. In other words, the reaction is called forth by new excitants and new modes of stimulation which give rise to mental complexes somewhat different from those caused by the earlier excitants. Thus, as we mentally develop, admirations having a richer ideational structure and more complexity of feeling-tone take the place of the first simple ones, which last die out or survive only as rudimentary processes. This enlargement of the field of exciting objects, with the concomitant differencing of the emotional state into a larger and larger number of shades, is the outcome of the whole process of mental growth. It means, first of all, the growing differentiation of the child’s experience, that is, of his perceptions and ideas, as well as the expansion of his reflective processes. In this way a modified admiration attaches itself to a new kind of object, _e.g._, works of art, virtuous actions, when these come to be perceived and reflected on in such a way as to disclose their admirable side. In all such extensions the emotional reaction remains in its essential elements one and the same experience. We may say, if we like, that the expression has been “transferred” to a new situation or a new experience, through the working of a force which has been called “the analogy of feeling”.[124] This process of extension by analogy of situation and attitude may be seen to be a constituent in the development of laughter. Taking its primitive form to be the expression of a sudden raising of the feeling-tone of consciousness to the level of gladness—which elevation may be supposed to {192} involve at least an appreciable sense of relief from a foregoing state of strain or oppressive dulness—we may readily see how the reaction is passed on, so to speak, to analogous mental attitudes which are developed later.