Sensation

Sensation, a state or modification of consciousness, supposed to be caused by a stimulus acting on the nervous system (q.v.) and transmitted to the brain through the afferent nerves. Sensations fall into three classes: (1) those which are attributed to the impact of some external object on the special organs of sense; (2) those which fall under the head of general sensibility, such as the comfort or discomfort attending the action of the digestive organs; (3) those which accompany muscular activity, the stimulus being apparently derived from the adjustment of the muscles, tendons, and joints. The Association psychologists commonly speak as though each sensation were a separable unit assignable to some one cause or agent, but against this view there is a twofold objection. In the first place, the single simple sensation is a mere ideal; practically every sensation contains representative elements, i.e. elements derived from past experience; and secondly, the interaction of the various factors which produce sensation is much greater than is commonly supposed. Thus there can be no doubt that in sensations of taste a tactile or olfactory element is frequently present. Again, the changes in quality which accompany the increase or decrease of the stimulus applied to a special sense point to a mysterious complexity which lies altogether beyond our present means of analysis. This observation may be extended to the sensations of pleasure and pain which arise in connection with those communicated through the sense organs. The correct view would therefore seem to be that sensation is a complex whole, the segregation of which into parts is due to reflection rather than intuition. On this ground it may be maintained that the phenomena of consciousness presented by the special senses are merely modifications of a fundamental mass of general sensation, but as yet we possess no clue which would enable us to trace the differentiation. [PSYCHOLOGY.]