Page:The New International Encyclopædia 1st ed. v. 10.djvu/759

* INSTINCT. «71 INSTINCT. changed environment. The instincts of young animals may be replaced by a new set. Kxamples are those of animals which pass through a mela- mori)hosi.s, as in the case of the caterpillar and butterlly, in which there are two sets or classes of instincts; i.e. (1) those by which the larva is enabled to live, and (2) the reproductive and egg-laying instincts of the butterfly. Thus, the same individual is born with a crop of innate congenital instincts, sheds them with its larval skin, so to speak, and then with the new birth of the butterlly appears a series of automatic and rellex habits and instincts which have arisen in response to the origin of the new structures, such as wings, sense organs, reproductive glands, genital armature, and the elaborate spiral tongue adapted for taking an entirely different kind of diet from that of the grossly feeding caterpillar. Nothing more plainly proves that instincts are not directly implanted by the direct interposition of a supernatural power, as is still insisted on by Fabre and Wasmaun, than that they are special in- nate or natural propensities, "transcending the general intelligence or experience of the creature," and arising from and dependent on peculiarities of structure and habits. Instincts are 'innate' and 'natural' because they have arisen by a natu- ral growth and have been acquired. The 'saga- city' of the ant, of the wasp, and of the bee is very wonderful ; but still more so when we realize the fact that it has evolved in response to the needs of the complicated organism of which it is the natural psychical outcome. The instinct of the most sagacious ant, bee, or bird may be, and is, occasionally at fault; birds may in certain cases change their nesting habits. On the other hand, certain spiders, insects, as well as birds and mamnuils, are known to 'rise with the occasion' to overcome obstacles, and to be guided, as we sayj by the germs of reason to act much as a human being would under similar circumstances. There are three grades of mentality; i.e. three steps in the evolution of mind. These are: (1) Reflex acts and tropisms; (2) instinctive acts; and (3) acts of reason. It is, as everybody knows, dilficult to draw the line of division be- tween these grades. It may be said, however, that what we call instincts are on the whole in- termediate between the simplest physiological or primary reflex acts, especially those resulting from some external stimulus of light, heat, grav- ity, odors, and sounds; i.e. the various tropisms (sec Tropism), and acts of intelligence and of reason. In short, animals are neither automata, nor are they as a rule guided by intelligence or reason, as in man. Let us first consider what are mere physio- logical or reflex acts ; i.e. tropisms. One example is the efforts of the young chick at pecking food. This is said by Lloyd IMorgan to be "a motor re- sponse to a certain stinuilus," which is purely mechanical or organic, and is imaccompanied by consciousness. Locb defines a reflex as "a re- action which is caused by an external stimulus." It is well known that plants, and also the lowest or simplest animals, turn to the light, are helio- tropic: that they also respond to the stimulus of cold, heat, hunger, and reproductive needs. They are also geotropic. They move in certain directions, take in food as if exercising the power of choice, though this is not the case. Thus the reflex acts which lie at the base of in- stinctive acts are, says Loeb, the various trop- isms. In this respect the lowest animals (proto- zoans, sponges, and polyps) are scarcely if any higher than plants. In the higher animals, as in man, winking is a reflex act, the closing of the eyelids is a reaction caused by an external stimu- lus, as when the conjunctiva is touched by a for- eign body, or when the pupil is narrowed under the influence of light ( Loeb). The result of experiments on the reactions of plants and animals to various external stimuli shows that irritability and conductibility "are the only qualities essential to reflexes," and it will be remembered that these are the common qualities of the protoplasm both of plants and animals. "The irritable structures at the sur- face of the body and the arrangement of the muscles determine the character of the reflex acts" (Loeb). Reflex acts apparently have a purposive char- acter. Examples of reflex acts in the whole ani- mal, the individual (not simply in distinct or- gans), are those actions related to the outer world and other organisms, manifested by proto- zoans, such as monads and amieba;, by sponges and polyps, as well as the ascidians. Their move- ments, modes of escaping danger, of getting food, or their deportment in freely moving forms in the presence of their prey or their enemies, their mode of conjugation, are acts in response either to external stimuli, such as light, heat or cold, odors, tastes, smells, or the effects of hunger or the reproductive functions. The Nature of Instinct. What has been said prepares the way for an attempt at an explana- tion of the nature of instinct. It is evident that this can only be understood after more thorough experiments and extended observations, both on reflex and instinctive acts, than have yet been made. It is certainly diflicult to draw a sharp line of demarcation between reflexes and instincts. As the result of recent experiments, Loeb regards instincts as inherited reflexes so purposeful and so complicated in character that nothing short of intelligence and experience could have produced them. These reflex acts, becoming habitual and persisting, through individual life, or at least a portion of it, result in what we call habits. ^■hat are called instinctive acts are manifested by animals ■higher' or more specialized than those above mentioned. We see them exhibited in the higher worms (annelids), the land-snails, and squid, perhaps the starfish and sea-urchin, etc., though these forms are on the border line. The Crustacea, spiders, and insects are guided by instinct, with here and there germs of intel- ligence, until we come to birds and mammals, which in some cases at least approach man in the capability of meeting or adapting themselves, as if by intention, to emergencies or to some end, this being an incipient form of reason. Defimtioxs of Insitinct. Herbert Spencer de- fines instinct ;is compound reflex action, and on an- other occasion as "a kind of organized memory." He argues that instinctive actions grow out of reflex, and in time pass into intelligent actions (Romanes), Samuel Rutler also asserts that instinct is 'inherited memory,' J. J. Murphy re- marks that "reason differs from instinct only in being conscious. Instinct is unconscious rea- son, and reason is consciotis instinct." Romanes defines instinct as "reflex action into which there is imported the element of consciousness." Pack-