Page:Popular Science Monthly Volume 33.djvu/619

Rh suggestion is very easily imposed; to the blind, hearing is decidedly the most valuable sense; and illusions and hallucinations of hearing are only slightly less frequent than those of sight. In general, the intellectual nature of these two senses presents a similar scale of individual differences, and suggests the action of like causes in their education as in their decay.

Third in importance is the group of muscular and tactual sensations accompanying motion. The importance of these is shown by the large factor of mere imitation in all training. The speaking of a language, though guided by the ear, and lost when hearing fails in childhood, is yet a separate acquisition, and deaf-mutes can be taught to speak by the muscular feelings alone. This avenue of knowledge was sufficient to bring to Laura Bridgman her phenomenal education. In common experience the value of this sense is illustrated by the tendency of many persons to speak to themselves, to move their lips when reading, to go through the motions of touching the keys of a piano when listening to a musical recitation. Many artists lay much stress on the teaching of free-hand movements apart from pencil and paper; singers often state that they "feel" an aria in their throats when they go over it to themselves; actors and athletes are, perhaps, likely to develop this kind of mental faculty, and among blind handicraftsmen it is frequent; while a certain school of psychologists define thinking as restrained action. The difficulty in estimating the importance of this sensory group to our intellectual fabric lies in the fact that it acts almost entirely under the guidance of the eye or of the ear; but analogy makes it probable that its importance varies much in different individuals. Such sensations enter into dreams, play a prominent role in hypnotism, where the assumption of an attitude will bring about the corresponding emotion, and have much to do in developing a common type of illusions and hallucinations. (Here belong the persecutions by crawling vermin, the feeling that the body is made of glass, or that the walls of the chest touch one another, and the like.)

Smell and taste need only a bare mention. The intellectual value of these senses reaches its climax in the lower animals. Smell is a richly suggestive sense (witness the associations with the odor of funeral flowers, and the like), and taste gives us many emotional epithets, such as a "sweet" disposition. But our mentality has developed in other directions, and these senses have remained nearest to the conæsthesic stage.

Every normal-minded man uses each of the above avenues of knowledge in his mental processes, as well in acquiring as in retaining and digesting mental food. Certain acquisitions depend