INSTINCT. - It is a tendency, an inner impulse, that determines and directs a complex of external, spontaneous and coordinated acts, by means of which the animal satisfies the needs of its life of relation. Instincts are at least as many as the various needs of the animal, and they may concern either a determined object (the fox that goes in search of the hare) or a determined action (the bird that builds the nest). They aim at a twofold purpose: the preservation of the individual, so that it seeks food (the spider, the ant-lion larva) or stores it up for the future (spies, ants) or defends itself from enemies (various forms of nest, color mimicry, feigned death, self-mutilation, migrations); and the preservation of the species (choice of safe places, provisions of different food for the offspring, training).
1. CHARACTERS OF INSTINCT
The empirical characters of instinct can be reduced to the following: 1) Adaptability to the particular ends to be attained. From this point of view the animal world, especially that of insects, displays marvels; nothing is more ingenious than the behavior of the beaver in building dams; of the bee in arranging and forming the hexagonal cells, solving the geometric and economic problem of obtaining that they contain the maximum of honey with the minimum expenditure of wax; of the leaf-rolling weevil, which cuts the birch leaf according to a formula of differential mathematics, discovered not long ago; of the ammophila, a vegetarian, which procures for its carnivorous larva a live butterfly caterpillar, but immobilized beforehand by stinging its nerve centers. 2) Blindness, in the sense that the animal does not know, under the aspect of end, the end that it nevertheless so admirably attains with its action, nor the proportion that the means it employs have to this end. It knows those movements that it performs, which are in fact so many means ordered to its own good or that of the species, but it does not perceive the end as such, nor the means as such. So true is this that either, the circumstances having changed or it being disturbed in its work, it continues to perform acts without noticing that they have become useless (the spider, for example, which carries and energetically defends its cocoon, continues to drag about and defend a cork ball substituted for the cocoon; birds feed the chicks for a certain time, then abandon them, even if, for lack of food, they see them die of hunger). 3) Specificity. Instincts are characteristic of the species. Every species of spider weaves the same type of web; every species of bird makes the same type of nest, so that one easily guesses the species of the bird from the characteristics of the nest. Sometimes there are acts characteristic within the same species, for example, the instinctive acts of the queen bee are different from those of the drones, which in turn do not have the instinct to make honey and produce wax. 4) Preformation, in the sense that instinct is innate, spontaneous, natural, not learned from experience; the ant-lion larva performs its work perfectly, as soon as it is hatched from the egg, without any prior training by the parents, who are no longer there; the duckling, hatched by a hen, runs at once to the water and dives into it swimming, despite the cries of the frightened broody hen; the squirrel lays up its store of hazelnuts for the first winter, which it does not know, as it will do for the succeeding winters. Here, however, one must distinguish between primary instincts and secondary instincts. The primary ones are those immediately perfect and not further perfectible (for example, pecking for chicks, suckling for mammals); secondary ones are those less indispensable, which can be perfected with exercise and experience (for example, birds learn to sing, dogs to seize their prey in this or that way; in migrations it is the older ones that lead the flight; all animals learn to fear the hunting rifle; many species of fish no longer bite at the hook, after one of them has been caught on it). And in general it is observed that the more the psychic life is developed, which happens the higher one rises in the scale of species, the more the automatic efficacy of instinct diminishes. This fact also permits the training and domestication of the higher animals, which by means of psycho-physiological habits lend themselves to bringing about in themselves new tendencies and capacities. 5) Immutability; that is, instincts always manifest themselves with the same activities (the bees of today work exactly as in the times of Virgil, who sang of them in the Georgics; the old individuals know as much as the young ones. Nevertheless one must also admit a certain degree of plasticity, of flexibility to the diversity of environmental circumstances (for example, the golden oriole now uses, to build its nest, threads woven by human hands; or it is certain that the art of weaving is not as ancient as man; the spider adapts its web to the diversity of the points of support, on which the individual webs are worked). 6) Coordination, in the sense that the instinctive acts, many times quite complicated and ingenious, and requiring time, are not carried out at random, but appear dominated and directed in function of the end to be attained and do not stop until it has been attained. They have therefore a finality toward which, even in their most complex diversity, they converge. 7) Correlation with development and with determined situations of the organism. Thus the instinct of preservation in insects with metamorphosis produces different behaviors according as the insect is in the state of caterpillar, of chrysalis, of perfect formation; the sexual instinct manifests itself after maturation and disappears after the involution of the reproductive organs; the worker bees pass from the behavior of nurses of the small larvae, which in the first days of life remain sedentary in their little cell, to that of producers of wax, when the glands secreting the nutritive liquid undergo an involution and those of the wax take on strong development, and finally to that of gatherers of honey, when the combs are formed; likewise the lack in food of necessary substances or indigestion arouses the search for other determined foods that are not sought outside those circumstances.
II. NATURE OF INSTINCT
From the consideration of the characteristics mentioned above, various conceptions have been derived concerning the nature of the instinct: 1) Mechanistic theory. Descartes, the mechanistic philosophers and the defenders of the theory of "tropisms" (J. Loëb, M. Verworn, etc.), who admit no third datum between matter and spirit, namely life, reduce the instinct to the purely physiological reflexes aroused by it and the animal to a pure automaton. This openly contradicts experience. The spider that repairs its web, torn by a gust of wind, the insect that remedies the incident that has arisen while it is building its little cell, demonstrate that circumstances can to a certain extent determine the insertion into the series of instinctive acts of a new act, which has become accidentally necessary in order to be able to continue and complete the instinctive cycle. Moreover, the modifications that, according to circumstances, the oriole knows how to make to its nest, the partridge to its refuge, demonstrate in the instinct a certain plasticity. But if the play of the acts is purely mechanical, it can neither be interrupted, nor completed, nor modified. The instinct presupposes reflexes either simple or associated, but is not confused with them; rather, it directs them to their goal. 2) Anthropomorphic theory. Other philosophers, on the other hand, and several naturalists, struck by the marvels of instinctive activity, would like to attribute to animals an intelligence like the human one, even if of a lower degree, even if rudimentary. Experience, however, teaches that the instinct does not require an intellectual cognition, which would no longer explain the uniformity and constancy of instinctive actions (v. further on, V). 3) Mystical theory. It sees in the instinct a mysterious intelligence, which has nothing to do with human intelligence, but is rather a kind of intuitionism, by which it is said, for example, that animals foresee the weather, cataclysms, and run to shelter; they eat because they intuit that otherwise they would die of inanition. However, these facts have quite another interpretation; animals have no intuition of the weather; but they are so made that certain particular sensations produce reflexes that prepare them for changes in the weather; thus they eat, because the sensation of hunger arouses those reflexes that drive them to seek food. 4) Psychological theory. Instinctive conduct, as it reveals itself from the typical forms indicated above, "is an activity that bears the imprint not only of a causal nexus between its various manifestations, and between these and the structures of the organism, but also of a direction toward an end and of an objective experience. It presents itself to us evidently as a whole, as an organized unity, directed toward an end, which, while it unfolds, is not yet in act, and, once reached, will mark its conclusion." And also in the subject that performs the action, one must suppose "an interior activity, sure and unconscious, which organizes in a determinate sense the raw datum, receptor and effector, of the organism, so as to connect it into a whole, which unfolds successively in time and space. It is therefore the direction, or rather the 'sense', the fundamental and characteristic note of the instinct; it must therefore be considered a psychological activity" (A. Gemelli-G. Zunini [v. bibl.], p. 340). This interior activity, which provokes the external activity and the movements and actions necessary to the end, is proper, according to St. Thomas and Scholastic philosophy, to a particular faculty that the animal possesses, of discerning what is suitable or harmful to it, and is called "estimative" (St. Thomas, De veritate, q. 18, a. 7, ad 7; De anima, lib. III, lect. 5).
III. FUNCTIONING OF INSTINCT
The instinct is conditioned by a twofold factor: a) the natural predisposition of the animal's organism (physiological aspect); b) perception, which may be either an internal organic sensation or a perception, accompanied by the corresponding representation, of an external object, e.g., the sight of a puddle, a cry, a song, an odor, etc. (psychic aspect). Therefore, by virtue of the animal's natural predisposition, certain objects provoke in it determinate representations and sensations, which set the instinctive tendency in motion, and then the animal acts under the impulse of these sensations and of the representations that accompany them; these, naturally, vary with the variation of the circumstances actually given and therefore cause the instinctive act to vary, adapting it to them. For example, the cat, in order to spring upon the mouse, does not always make the same leap, but proportions it to the distance, to the immobility or movement of the prey; the jellyfish, which fails to immobilize its victim at the first sting, repeats it. This explains the wariness that is observed in the actions of animals, which is an appraisal of the forms of the object, of spatial relations, of the movements to be made or omitted or redone.
IV. ORIGIN OF INSTINCT
According to the various ways of conceiving the nature of instinct, the theories devised concerning its origin are various, and they can be grouped as follows: 1) Theory of adaptation: instinct would derive from the necessity, for the animal, of adapting itself to external conditions; a kind of struggle for life under the alternative of adapting or dying (J. B. Lamarck, C. Darwin, H. Spencer, etc.). This cannot be, because animals (the bee that makes the cells, the sheep that flees the wolf) would have perished before they could have adapted. 2) Theory of individual habit: instinct is caused by the habit contracted of always acting in that determined way, whether by reason of one's own experience, or of imitation, or of education (S. Condillac, R. Russel-Wallace, etc.). To this one may observe that instinct already exists from the very first instinctive operation (the bird builds its first nest with the same ease and perfection as the subsequent nests; the sheep flees the wolf from the very first time it sees it). If instinct were the fruit of education, the first time it would not act as perfectly as the second, third, etc., unless one wishes to attribute to animals, which perform such complex and marvelous instinctive acts, a capacity for learning such as to succeed immediately there where man would have to spend much more time; imitation, moreover, cannot take place at least in those cases in which, for example, insects have no way of seeing even for an instant their parents, who die before the larva emerges from the egg. This does not prevent acquired automatisms from being inserted into an instinctive act, thus complicating its interpretation. 3) Theory of hereditary habit: instinct would be transmitted by the parents to the offspring (thus in general the evolutionists). But then it would not be explained from whom the progenitors of that determined species could have inherited the instincts transmitted; moreover, if some instincts can perhaps be inherited, for many inheritance explains nothing, for example, the queen and the drones of the bees do not work, but generate; the worker bees, on the other hand, generated by them, work with marvelous art and do not generate. 4) Theory of perception: instinct would be produced by the perception of external objects. But one must observe that perception is a factor necessary to set instinct in motion, and therefore does not create it, but presupposes it; moreover the external senses do not perceive the reason of utility, otherwise how is it that the bird gathers straws for the nest only at determined epochs of the year and not on the other days, on which it likewise sees the same straws of the same color? Why does the sparrow choose straw, and the swallow mud, for building the nest?
The origin of instinct, like that of intelligence and will, postulates the solution of the problem of the nature of life and of its finality; it cannot therefore stop at experimental science alone, but must ascend to metaphysics, which treats precisely of the origin of living beings, of the faculties with which they were enriched by their supreme Author in relation to the ends assigned to each species of them.
V. INSTINCT IS NOT INTELLIGENCE
That animals possess intelligence is already an ancient opinion, affirmed, at least implicitly, by the supporters of the transmigration of human souls into beasts; and it is upheld, also in later times, by H. Rorarius and M. Montaigne; in recent times by the champions of so-called "folk psychology" (A. Brehm, G. J. Romanes) on the traces of C. Darwin, and then by those evolutionist naturalists who classify the actions of animals into two orders: those performed in a manner conformable to the end, but antecedently to all experience, would belong to instinct, which would act mechanically; those, on the other hand, performed by virtue of their own experience, would belong to intelligence, which would differ from human intelligence only in degree.
Philosophy, on the other hand, and the more accurate study of the phenomena offered by experience, conducted by distinguished naturalists (e.g., J. H. Fabre, G. Surbled, L. T. Hobhouse, J. B. Watson, J.-A. Plateau, W. Wagner, E. Claparède, J. Lubbock, W. Wundt, E. L. Thorndike, A. J. Kinnaman, etc.) assert with certainty that the operations of brute animals do not proceed from intelligence, because of this they give no sign that proves its presence or its necessity; indeed they give signs of not possessing it at all. And by intelligence is understood the faculty of forming and comprehending abstract, universal concepts, of knowing the relations existing between effect and cause, between means and end, of formulating judgments and reasonings and not merely of associating different representations; and finally of reflecting on one's own actions with a view to continuous adaptation and perfecting.
Now intelligence, precisely because it is directed in its operations by abstract and universal concepts, is not limited to a single kind of operability; for example, one who is directed by the abstract idea of "house" does not limit himself, in order to build it, to a single material only (e.g., wood), nor to a single type; whence the possibility that the same architect builds edifices according to the most varied styles. In animals, on the contrary, the individual species and sometimes even the individual subspecies have only one kind of operability, and all the individuals that belong to them carry it out in the same way; instinctive acts are uniform and constant.
Furthermore, among the gifts of intelligence are counted language, progress, the notion of a God and of a moral law, the tendency toward supersensible goods — all gifts that are not found in animals. These, in fact: 1) do not have the true faculty of language, which supposes knowledge of the external signs (word or gesture) that are used, nor of the relations that pass between word and word, gesture and gesture, nor of the purpose for which one speaks and gestures and seeks to communicate to others one's ideas and one's knowledge. They have, yes, an appearance of language (shouts, whines, hisses, whistles, etc.), but it is nothing other than an exteriorization of their internal appetites and affections, which in turn arouse in other animals similar appetites or affections or tendencies of imitation or associations suited to making them act in this or that way, in this or that direction. The brooding hen, for example, with certain cries warns of danger; at those cries the chicks run to shelter under her wings; thus the sentinels of gulls, partridges, lapwings, marmots utter a cry at the approach of a danger. That cry manifests the passion, the affection aroused in the hen or in the sentinel by the danger. It will also produce the effect of putting the chicks or the companions on guard; but in itself the cry is nothing but a pure psychological phenomenon; a psychological phenomenon is the running away of the chicks, a manifestation of the affection produced in them by that particular cry of the hen. In other words, it is one thing for nature to direct the hen's cry to the safety of the chicks, another thing for the hen with that cry to intend to give a warning, to call the chicks, as a mother would do with her little children. "Etsi bruta animalia aliquid manifestant non tamen manifestationem intendunt; sed naturali instinctu aliquid agunt ad quod manifestatio sequitur" (Summ. theol., 2ᵃ-2ᵃᵉ, q. 110, a. 1). Thus are explained all those expressions of brute animals that we perceive as directed to others, as signals. In fact they serve as signals, but the brute animal does not perceive them as such, does not use them with the purpose of warning others; the directing is only affective and material, not intellective and formal. The same may be said of the supposed language of bees, of ants that attract their companions to where they have found an abundance of honey or sugar or grain. The fact can be explained by the muzzle-touchings, or mouthings or pawings provoked on the one hand by the satisfaction of having found something good and on the other by the perception that those gestures arouse in the instinctive action of rushing to the fortunate spot. One cannot therefore assert either that brute animals speak, nor, much less, that they understand one another. To understand one another there would be needed an agreement about the meaning of that cry, of that particular movement. But this agreement does not intervene, for example, the first time the chick hears the hen's alarm, or the kitten sees the dog. 2) Brute animals, moreover, are not capable, except of those progresses that derive from the association of images and from memory; they do not, in fact, modify their way of acting, except by virtue precisely of these organic and sensitive faculties. While man marks multiform variations and progresses in the sciences and arts, in brute animals there can be only variations of practical, accidental procedures, within the circle of the variations of an organ fixed in its specific structure; it can never free itself in its actions from the style and the measure imposed by nature on its appetite, on its imagination, on its very inventiveness. 3) Brute animals, as daily experience attests, manifest no sign of tendency toward supersensible things, nor any sign of religion or of moral law. Otherwise one would not see them continually indulging their appetites, abandoning or killing sick individuals, as is regularly observed in many species, nor, as in others, the female always devouring the male after the reproductive act.
At times there are noted, it is true, in brute animals actions that would seem to bear a morality, such as obedience, gratitude, repentance, love toward the master, even to the point of exposing themselves for him to the danger of life, or dying on his tomb; but these actions have only an apparent resemblance to the acts of the true virtues; in reality they proceed only from sensitive affection, from the memory of past facts and circumstances, for example, from love, from the memory of past pleasures, from fear, etc.
To wish to consider many attitudes of animals as forms, even if primitive, of intelligence, clashes also with what the morphology and physiology of the brain say. It is by now clearly demonstrated that the higher psychic functions, and among these the foresight of the future and foreknowledge in that regard, and acts of will, etc., are linked in man with the presence of definite cortical parts of the cerebral hemispheres, localized especially in the frontal lobes and in the prefrontal cortex. These cortical parts are absent in all animals, even in those, such as the anthropomorphic apes, morphologically more similar to man. It is a known thing how the destruction of these centers in man leads to the loss of all intellective acts, and therefore intelligence cannot be attributed to beasts, which are normally deprived of these centers.
To complete the argument, one may mention certain famous animals that were held up as examples of intelligent brutes: the Berlin horse Hans, the horses of Elberfeld, the dog of Mannheim, the monkeys Maia of Vienna and Basso of Frankfurt, etc., which by striking their hooves, by moving tablets bearing the letters of the alphabet or numbers, etc., demonstrated that they could read, understand a language, distinguish people by name, and perform very difficult mathematical operations. But a careful examination of the circumstances also showed that these were mere automatisms, directed by movements or signals of the persons present and especially of those who had trained them. Indeed, once the circumstances were changed, the apparently intelligent actions ceased, or were carried out at random, with continual mistakes (cf. on the subject: A. Gemelli, Bestie che pensano e fanno i conti... e uomini che non ragionano, in Religione e scienza, Milan 1920, pp. 51-108; id., L'intelligenza delle scimmie, in Scienza ed apologetica, ibid. 1920, pp. 301-33; E. Claparède, Les chevaux pensants d'Elberfeld, in Arch. de psychologie, 12 [1912], p. 263 ff.; 13 [1913], p. 244 ff.; id. and J. Largnier, A propos du chien de Mannheim, ibid., pp. 312-98).
Regarding this whole question of the marvelous feats of brutes, which appear to presuppose the presence of an intellectual faculty, it must be borne in mind: that the facts must be carefully examined in order to separate the pure truth from the anthropomorphic interpretations with which they are presented and embellished; that the fact must not be an isolated one, so as to be able to exclude purely chance occurrences; that one must first seek the explanation in the sensory faculties, i.e., memory, etc. By carefully following these rules, it will be ever more clearly established that instinct is never intelligence.
VI. INSTINCT IN MAN
In man too, since he is an animal, there are instincts, and they manifest themselves from earliest infancy. Indeed, one observes in the child the instinct to suck, to swallow, to move about and walk; the gregarious instinct, that is, the impulse to want to be in the company of others; the instinct of fear at a sudden sound, at the appearance of an unknown person; the instinct to turn to its mother and rest quietly in her arms. It manifests its states of mind with weeping, cries, clamor, smiles, caresses. However, man, endowed with intelligence, easily exercises a kind of "censorship" over his instincts, and little by little subjects them to the empire of reason and will; so that they gradually lose their character of "animality" to take on that of inclination (v.). Hence it is customary to say that man has less instinct-ability than animals and more instinct-inclinations. This is the reason why man's instincts appear in full and often even in anomalous form in individuals impeded in the use of intelligence, for example, in imbeciles and cretins; whereas in the normal child they appear in their natural purity.
VII. THE LAWS OF INSTINCT
Instincts are subject to certain laws, which offer important consequences in the field of pedagogy. 1) Law of caducity: many instincts, present and operative in the first years of life, cease later, merely through the evolution of the organism; thus, for example, chicks, after a certain number of days, no longer feel stimulated to shelter under the hen's wings when she warns them of danger. 2) Law of specialization: every instinct that has once found its full satisfaction in a determined object remains exposed to taking exclusive pleasure in it and therefore to losing its spontaneous impulse toward other objects of the same kind; hence the exclusive love for a place (the bird rebuilds its nest on the same branch), the "irrational" sympathies or antipathies for determined persons or actions. In these cases the instinct tends to transform itself into an acquired inclination. 3) Law of confluence: if a determined object arouses two contradictory instincts, the fact of developing one will have as its consequence the fact of inhibiting the other and rendering it as it were stillborn. For example, a chick feels two contradictory impulses: to follow or to flee a person. If from the very first day it is accustomed to follow that person, it will no longer feel toward that person the instinct of fear, which usually arises on the fourth day. 4) Law of survival: if the instinct has been able to function in the period when its dynamism was at its maximum, it will be increased by a habit, which will continue to live and to react even after the instinct has disappeared. Instincts exercised at the maximum in one direction (e.g., the instinct of play, of sport) produce a particular attachment to this or that game or amusement. 5) Law of inhibition: an instinct cannot be neutralized, before the period of its caducity, except by the development of the contrary instinct. Thus the fear of punishment can impede the development of a certain number of instincts that are not good.
VIII. THE PEDAGOGY OF INSTINCT
The laws mentioned above offer the educator certain very important norms, which have their repercussion on the whole of life: 1) instincts must be watched over and directed from their very first appearance. Families therefore must keep children under their eyes as much as possible; only thus will they be able, on noticing bad tendencies, to remedy them, by removing from them the objects that can serve as an impulse to evil and offering instead to good tendencies the objects that serve to develop them. Persons outside the family rarely perform this office well; and within the family itself no one does it better than the mother, whose heart is richest in intuitions and in expansiveness. 2) One must watch for the appearance of useful tendencies in order to offer them continual occasion to exercise themselves therein, spurring to their maximum strengthening those that will be most useful for the future. 3) Remove from the child everything that can represent a danger both for the present and for the future (e.g., the child's combativeness is not always well served by excessively indulging it with little swords, bows, revolvers and with everything that smacks of violent overpowering). 4) One must not confuse danger with pain. Nothing is more effective than associating pleasure and pain with the exercise of the instincts, according as one wishes to encourage or repress them. The pain that derives from or follows the exercise of a harmful action has a great inhibitory power. Certainly the inhibitory power par excellence is the activity of the will, enlightened by the wise reasons set forth by the intellect; but even remaining within the sensitive zone, sorrow and punishment admirably flank the weakness of the will. 5) One must not exaggerate the fear of risk and of pain; otherwise one will form inert, selfish, uncomprehending persons, whereas nothing is more educational and formative than the lived experience of pain.