When a thing is seen or heard (or smelled or tasted or thought), it arouses an emotion; that emotion consists of at least three parts. First, the arousal of memories and experiences that give it a value to the individual, make it a desired object or a dreaded, distasteful object. Second, at the same time, or shortly preceding or succeeding this, a great variety of changes takes place in the organism, changes that we shall call the vaso-visceral-motor changes. This means merely that there is a series of reactions set up in the sympathetic nervous system, in the blood vessels and bodily structures they control and in the glands of internal secretion,--changes which include the blush or the pallor, the rapid heartbeat, the quickened or labored breathing, the changes in the digestive tract which include the vomiting of disgust and the diarrhoea of fear; the changes that passion brings in the male and the female and many other alterations to be discussed again. Third, there is then the feeling of these coenaesthetic changes,--a feeling of pleasantness, unpleasantness mingled with the basic feeling of excitement, and from then on that situation is linked in memory with the feeling that we usually call the emotion but which is only a part of it. Nevertheless, it becomes the part longed for or thereafter avoided; it is the value of the emotion to us, as conscious personalities, although it may be a false, disastrous, dangerous value. Excitement is the generalized mood change that results in consciousness in consequence of the vaso-visceral-motor changes of emotion; it is therefore based on bodily changes as is the feeling, pleasant or unpleasant, that also occurs. William James said that we laugh and are therefore happy; we weep and are therefore sad; the bodily changes are primary and the feeling secondary. We do not accept this dictum entirely, but we say that the organism reacts in a complicated way and that the feeling--sadness, disgust, anger, joy--springs from the memories and past experiences aroused by a situation as well as from the widespread bodily excitement also so aroused.
For the neurologist both the cerebral and the sympathetic-endocrinal components of emotion are important.
For the moment we turn to instinct and instinctive reactions.
2. Man has always wondered that things can be known without teaching. So slow and painful is the process of mastering a technique, whether of handicraftsmanship or of art, so imbued are we with the need of education for the acquirement of knowledge, that we are taken aback by the realization that all around us are creatures carrying on the most elaborate technique, going through the most complicated procedures and apparently possessed of the surest knowledge without the possibility of teaching. The flight of birds, the obstetric and nursing procedures of all animals, and especially the complicated and systematized labors of bees, ants and other insects, have aroused the wonder, admiration and awe of scientists. A chick pecks its way out of its egg and shakes itself,--then immediately starts on the trail of food and usually needs no instruction as to diet. The female insect lays its eggs, the male insect fertilizes them, the progeny go through the states of evolution leading to adult life without teaching and without the possibility of previous experience. Since the parent never sees the progeny, and the progeny assume various shapes and have very varied capacities at these times, there can be no possible teaching of what is remarkably skillful and marvelously adapted conduct.[1]
[1] The nature of instinct has been a subject of discussion for centuries, but it is only within the last fifty years or thereabouts that instinctive actions have really been studied. I refer the reader to the works of Darwin, Romanes, Lloyd Morgan, the Peckhams, Fabre, Hobhouse, and McDougall for details as to the controversies and the facts obtained.
Herbert Spencer considered the instinct as a series of inevitable reflexes. The carrion fly, when gravid, deposits her eggs in putrid meat in order that the larvae may have appropriate food, although she never sees the larvae or cannot know through experience their needs. "The smell of putrid meat attracts the gravid carrion fly. That is, it sets up motions of the wings which bring the fly to it, and the fly having arrived, the smell, and the contact combined stimulate the functions of oviposition."[1] But as all the critics have pointed out, the theory of compound reflex action leaves out of account that there are any number of stimuli pouring in on the carrion fly at the same time that the meat attracts her. The real mystery lies in that internal condition which makes the smell of the meat act so inevitably.
[1] Hobhouse.
In fact, it is this internal condition in the living creature that is the most important single link in instinct. In the non-mating season the sight of the female has no effect on the male. But periodically his internal organs become tense with procreative cells; these change his coenaesthesia; that starts desire, and desire sets going the mechanisms of search, courtship, the sexual act and the care of the female while she is gravid. All instinctive acts have back of them either a tension or a deficit of some kind or other, brought about by the awakening of function of some glandular structure, so that the organism becomes ready to respond to some appropriate outside stimulus and inaccessible to others. During the mating season, with certain animals, the stimulus of food has no effect until there is effected the purposes of the sexual hunger. Changes in the body due to the activity of sex glands or gastric juices or any other organic product have two effects. They increase the stimulation that comes from the thing sought and decrease the stimulation that comes from other things. In physiological language, the threshold for the first is lowered and for the other it is raised.
