It is probable that the sensations included under the head of ticklishness are not all of the same quality. It seems safe to say that in all cases the sensation is complex to this extent, that it is composed of a tactile and an organic factor. But we may see that the complexity is often greater than this. An obvious instance is the addition {54} of a peculiarly irritating effect when the orifice of the ear or nostril is tickled, an effect due to the action of the stimulus on the hairs, which are specially abundant here.[36] Some surfaces, too, which are free from hair, appear to be endowed with a special modification of the ticklish sensibility. In my own case, at any rate, light touches on the sole, have, as long as I can remember, excited sensations which seem to have almost a character of their own. A further complication probably occurs when the tickling grows rougher and approaches to a digging of the fingers into the soft parts of the armpits; for here the nerve-endings lying deeper are pretty certainly stimulated. Lastly, it is important to add that prolongation of the tickling seems to introduce changes in the intensity, if not also in the quality of the sensations. Hence it would appear that the sensations falling under the head of ticklishness, though they have certain common characteristics, may vary considerably. Since we are here concerned with these sensations as provocatives of laughter, it behoves us to look rather closely at their feeling-tones. As largely organic sensations they may be expected to have a strongly marked element of the agreeable or disagreeable; and this is what we find. I, at least, cannot conceive of myself as having the proper sensational experience of tickling, and yet being wholly indifferent. When, however, we ask what is the precise feeling-tone of one of these sensations, we find no simple answer forthcoming. Some psychologists view them as having, in general, an unpleasant character.[37] On the other hand, children are {55} certainly fond of being tickled, ask for it, and make a pastime of it. This at once suggests that we have here to do with a complexity of feeling-tone, as, indeed, our study of the sensations would lead us to suppose. It is, I think, a plausible supposition that no sensation coming under the head of tickling is merely agreeable or disagreeable. It seems always to be of a mixed feeling-tone: some sensational elements being pleasant, others unpleasant, though analysis may be unable to attribute with exactness their respective tones to the several elements.