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Encyclopedia Britannica - Main :: I27-INV |
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INSTINCT . It is in the first place desirable to distinguish 4eAween the word " instinct " (Lat. instinctus, from instinguere, to *cite, impel) as employed in general literature and the term" instinct " as used in scientific discourse. The significance of the former is somewhat elastic, and is in large measure determined by the context. Thus in social relationships we speak of " instinctive " liking or distrust; we are told that the Greeks had " instinctive " appreciation of art; we hear of an instinct of reverence or " instinctive " beliefs. We understand what is meant and neither desire nor demand a strict definition. But in any scientific discussion the term instinct must be used within narrower limits, and hence it is necessary that the term should be defined. There are difficulties, however, in framing a satisfactory definition. That given by G. J. Romanes in the 9th edition of the Encyclopaedia Britannica runs as follows: " Instinct is a generic term comprising all those faculties of mind which lead to the conscious performance of actions that are adaptive in character but pursued without necessary knowledge of the relation between the means employed and the ends attained." This has been criticized both from the biological and from the psychological standpoint. From the biological point of view the reference of certain modes of behaviour, termed instinctive, to faculties of mind for which " instinct " is the generic term is scarcely satisfactory; from the psycho-logical point of view the phrase " without necessary knowledge of the relation between the means employed and the end attained " iS ambiguous. (See INTELLIGENCE OF ANIMALS.) In recent
interest
absence of consciousness, it is none the less desirable, in the interests of psychology, to state that truly instinctive acts (as defined) are accompanied by consciousness. This marks them off from such reflex acts as are unconsciously performed, and from the tropisms of plants and other lowly organisms. There remains, however, the difficulty of finding any satisfactory criterion of the presence of consciousness. We seem forced to accept a practical criterion for purposes of interpretation rather than one which can be theoretically defended against all adverse criticism. We have reason to believe that some organisms profit by experience and show that they do so by the modification of their behaviour in accordance with circumstances. Such modification is said to be individually acquired. To profit by individual experience is thus the only criterion we possess of the existence of the conscious experience itself. But if hereditary behaviour is unaccompanied by consciousness, it can in no wise contribute to experience, and can afford no data by which the organism can profit. Hence, for purposes of psychological interpretation it seems necessary to assume that instinctive behaviour, including the stimulation by which it is initiated and conditioned, affords that naive awareness which forms an integral part of what may be termed the primordial tissue of experience.We are now in a position to give an expanded definition of instinctive behaviour as comprising those complex groups of co-ordinated acts which, though they contribute to experience, are, on their first occurrence, not determined by individual experience; which are adaptive and tend to the well-being of the individual and the preservation of the race; which are due to the co-operation of external and internal stimuli; which are similarly performed by all members of the same more or less restricted group of animals; but which are subject to variation, and to subsequent modification under the guidance of individual experience. Conscious concomitant. If a brief definition of instinct, from the purely biological point of view be required, that given in the Dictionary of Philo
sophy and Psychology may be accepted: " An inherited Defll- reaction of the sensori-motor type, relatively complex lions. and markedly adaptive in character, and common to a group of individuals." Instinctive behaviour thus depends solely on how the nervous system has been built through heredity; while intelligent behaviour depends also on those characters of the nervous system which have been acquired under the modifying influence of individual relation to the environment. Such definitions, however, are not universally accepted. Wasmann, for example, divides instinctive actions under two groups: (I) those which immediately spring from the inherited dispositions; (2) those which indeed proceed from the same inherited dispositions but through the medium of sense experience. The first group, which he regards as instinctive in the strict acceptance of the term, seem exactly to correspond to those which fall under the definition given above. The second group, which he regards as instinctive in the wider acceptance of the term, nearly, if not quite, correspond to those above spoken of as intelligentthough he regards this term as falsely applied (see INTELLIGENCE OF ANIMALS). By using the term instinctive in both its strict and its wider significance, Wasmann includes under it the whole range of animal behaviour.It will be seen that from the biological standpoint there fall under the stricter definition those hereditary modes of behaviour which are analogous to hereditary forms of structure; and that a sharp
drawn
is thus rendered definite through heredity, and the behaviour the distinguishing characteristics of which are acquired in the course of individual life. What in popular usage are spoken of is the instincts of animals, for example, the hunting of prey by foxes and wolves, or the procedure of ants in their nests, are generally joint products of hereditary and acquired factors. Wasmann's comprehensive definition so far accords with popular usage. But it tends to minimize the importance of the dis- tinction of that which is prior to individual experience and that which results therefrom. It is the business of scientific inter- pretation to disentangle the factors which contribute to the joint-products. It is indeed by no means easy to distinguish between what is dependent on individual experience, and what is not. Only the careful observation of organisms throughout the earlier phases of their life-history can the closely related factors be distinguished with any approach to scientific accuracy. By the patient study of the behaviour of precocious young birds, such as chicks, pheasants, ducklings and moorhens, it can be readily ascertained that such modes of activity as Examples running, swimming, diving, preening the down, scratch- from bird fife. ing the ground, pecking at small objects, with the characteristic attitudes expressive of fear and anger, are so far instinctive as to be definite on their first occurrence--they do not require to be learnt. No doubt they are subsequently guided to higher excellence and effectiveness with the experience gained in their oft-repeated performance. Indeed it may be said that only on the occasion of their initial performance are they purely instinctive; all subsequent performance being in some degree modified by the experience afforded by previous behaviour of like nature and the results it affords. It should be remembered that such comparatively simple activities, though there is little about them to arrest popular attention, are just the raw material out of which the normal active life of such organisms is elaborated, and that for scientific treatment they are therefore not less important than those more conspicuous performances which seem at first sight to call for special
But in the " homing " of pigeons there is little question that the experiential factor predominates. The habit results mainly from the modification of the higher nerve-centres through individual and intelligent use.. In the migration of birds we are still uncertain as to the exact nature and proportional value of the instinctive and intelligent factors. The impulse to migrate, that is to say, the calling forth of specific activities by climatal or other presentations, appears to be instinctive; whether the direction of migration is in like manner instinctive is a matter of uncertainty; and, if it be instinctive, the nature of the stimuli and the manner in which they are hereditarily linked with responsive acts is unexplained. To say that it is due to hereditary experience is generally regarded as inadmissible. For modern interpretation hereditary modes of behaviour afford experience; in no other sense can it be said that experience is inherited. A good example of the methods of recent
chief
Granted that instinctive modes of behaviour are hereditary and definite within the limits of congenital variation, the question of their manner of genesis is narrowed to a clear issue. Do they originate through the natural selection of orlon of origla. those variations which are the more adaptive; or do they originate through the inheritance of those acquired modifications which are impressed on the nervous system in the course of individual and intelligent use ? Romanes, taking up the inquiry where Darwin left it, came to the conclusion that some instinctive modes of behaviour which he termed " primary " are due to the operation of natural selection alone; that others, which he termed " secondary," and of which he could give few examples, were due to the inheritance of acquired modifications from which, in the phrase of G. H. Lewes, the intelligence had Examples from insect fife. lapsed; while others, which he termed " blended," were partly due to natural selection and partly resulted from the inheritance of acquired habit. There has been a prolonged controversy between the school of interpretation, commonly spoken of as Lamarckian, which advocates a belief in the inheritance of acquired characters, and the school, with Weismann as their leader, which questions the evidence for, or the probability of, such inheritance. The trend of modern opinion appears to be in the direction of the Weismannian interpretation. And it must be regarded as questionable, if not improbable, that instinctive modes of behaviour are in any degree directly due to the inheritance of habits intelligently acquired. That intelligent habits may secure the survival of those organisms whose germ-plasm bears the seeds of favourable congenital variations is not improbable. But in that case intelligent procedure only contributes to the survival and not to the origin of hereditary variations.To test the hypothesis that natural selection is an essential condition to the genesis of instinctive behaviour it should be the cruets! aim of investigation to find crucial cases. This is, mares- however, no easy task. We ought to be able to adduce stuns. cases in which, where the incidence of natural selection is excluded, acquired habits do not become instinctive. But it is difficult to do so. It seems, however, that in young chicks drinking from still water is a habit acquired through imitation of the acts of the hen-mother. The presentation of such water to sight does not evoke the appropriate instinctive response, while the presentation of water taken into the bill does at once evoke a characteristic response. Now it would seem that in the former case, since the hen " teaches " all her chicks to peck at the water, she shields them from the incidence of natural selection. But though the hen can lead her young to peck at the water, she cannot" teach " them how to perform the complex movements of mouth, throat and head required for actual drinking. In this matter they are not shielded from the incidence of natural selection. Thus it would seem that, where natural selection is excluded, the habit has not become congenitally linked with a visual stimulus; but where natural selection is in operation, the response has been thus linked with the stimulus of water in the bill. If this interpretation be correct we have here an example of the manner in which imitation plays an important part in the /mka- formation of habits which though oft-repeated are trop. not transmitted as hereditary instincts. But the imitative act is itself instinctive. The characteristic feature of the imitative act, at the instinctive level, is that the presentation to sight or hearing calls forth a mode of behaviour of like nature to, or producing like results to, that which affords the stimulus. The nature of instinctive imitation needs working out in further detail. But it is probable that what we speak of as the imitative tendency is, in any given species, the expression of a considerable number of particular responses each of which is congenitally linked with a particular presentation or stimulus. The group of instincts which we class as imitative (and they afford only the foundations on which intelligent imitation is based) are of biological value chiefly, if not solely, in those species which form larger or smaller communities. The study of instinct is in the genetic treatment of evolutionary science a study in heredity. The favouring bionomic conditions Relation are those of a relatively constant environment under to which relatively stereotyped responses are advantage-heredity. ous. If the environment be complex, there is a corre- sponding complexity in instinctive behaviour. But adjustment to a complex environment may be reached in two ways; by instinctive adaptation through initially stereotyped behaviour; or by plastic accommodation by acquired modifications. The tendency of the evolution of intelligence is towards the disintegration of the stereotyped modes of response and the dissolution of instinct. Natural selection which, under a uniform and constant environment, leads to the survival of relatively fixed and definite modes of response, under an environment presenting a wider range of varying possibilities leads to the survival of plastic accommodation through intelligence. Thisplasticity is, however, itself hereditary. All intelligent procedure implies the inherited capacity of profiting by experience. Instinctive in the popular sense, it does not fall within the narrower definition. of the term; it is more conveniently described as innate. It is important to grasp clearly the distinction thus drawn
See C. Lloyd Morgan, Habit and Instinct (1896), and Animal Behaviour (1900); G. J. Romanes, Mental Evolution in Animals (1883), and Natural History of Instinct (1886); Lord Avebury, On the Instincts of Animals (1889); Marshall, Instinct and Reason (1898); Mills, Nature of Animal Intelligence (1898); St George MVlivart, Nature and Thought (1882), and Origin of Human Reason (1899); E. Wasmann, Zur Entwickelung der Instincie (1897), Instinct and Intelligenz im Tierreich (1899, Eng. trans. 19o3); G. and C. Peckham, Instincts and Habits of Solitary Wasps (1898); see also the bibliography (section " Instinct and Impulse ") in Baldwin's Diet. of Philosophy and Psychology. (C. Li. M.) End of Article: INSTINCT If you wish, you can link directly to this article.
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