The twenty or more distinct kinds of sensations, into which modern psychology has elaborated the old five senses, can be observed to differ very widely in the degree to which they are susceptible of and accompanied by pleasantness and unpleasantness. The higher senses, sight and hearing, in most persons seem to yield sensations which vary much less from neutrality or indifference than the others. We must be careful to understand this difference correctly however. An arrangement of colours and shapes, a sequence of notes or a musical phrase may, of course, in suitable people, be as intensely toned, pleasantly or unpleasantly, as any organic or taste sensations, for example. But even this is not usual. The right experiment is to compare a single colour, say, or a single note, with such a sensation as a uniform touch or temperature gives rise to, a bath for example, or with a simple uniform taste or smell, or with hunger, or nausea. Fair comparison is difficult, equivalent levels of simplicity and uniformity being impossible to discover, but few will doubt that the degree of pleasure-unpleasure aroused by tastes, for example, far exceeds that which auditory or visual sensations excite by themselves. We must of course be careful here to avoid confusing the intrinsic pleasure-unpleasure of the sensations with that which arises through memory, through the effects of other sensations, pleasant or unpleasant, which may have accompanied them in the past, and through expectations agreeable or disagreeable.