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Christopher D. Green
York University, Toronto, Ontario
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By William H.R. Rivers (1920)
Posted March 2000
INSTINCT AND SUPPRESSION
I propose in this chapter to consider a little more fully some features of suppression to which I have already referred in connection with the "all-or-none" principle. Some of the instinctive modes of reaction to danger which I have described would fall short of their full effect, or would even fail altogether, if they were not accompanied by the complete suppression of tendencies to other kinds of reaction and of any conscious states associated therewith.
Thus, the reaction to danger, which may be regarded as natural to the healthy man, a reaction characterised by complete absorption in the immediate task by which the danger may be averted, would be impossible if complete suppression, not only of any tendency to the reaction of flight, but also of any trace of the emotion of fear which is its normal conscious accompaniment, did not occur. A man whose attention is wholly absorbed in the business of flying an aeroplane, or directing the movements of a company of soldiers, would certainly fall short of full efficiency if his movements were complicated by impulses to flight or his composure disturbed by even a trace of fear.
I have suggested that this normal reaction to danger has been inherited by man from his arboreal ancestors. When these ancestors took to an arboreal existence the reaction to danger by flight, which had previously involved the simple and wholly instinctive movements of running, now required the delicate adjustments of eye and limbs involved in movements from branch to branch and from tree to tree. Any animal in which such movements were complicated by impulses to the simpler motion of running, or whose consciousness was disturbed [p. 67] by the emotion of fear, would certainly fail to perform successfully the complicated movements of its arboreal existence. Accidents of various kinds would furnish means by which a rigorous process of selection would eliminate those animals which were unable to suppress their instinctive tendencies and any conscious affective states derived from their earlier mode of existence on the ground. It is evident that such adaptation to an arboreal existence by the suppression of inappropriate instinctive tendencies would have but poor chances of success if the mechanism of suppression only came into existence in order to meet the special conditions with which the arboreal tyro was confronted. The process of suppression could only be expected to succeed if it had been developed to meet other needs and was already there, only waiting to be employed in helping the animal to overcome the obstacles presented by a new mode of existence. We can be confident that the mechanism of suppression had already come into being in the ancestors of the tree-dweller long before there arose the needs due to a life above the ground.
In our search for conditions which could have brought the need for suppression, let us continue to deal with the instinctive reactions to danger. One of these clearly brings out the need for suppression. The reaction to danger by means of immobility is one which would obviously be impossible if the inhibition which led the animal to become motionless were complicated by the presence of impulses to movement, and especially to those pronounced and violent movements which make up the other great fundamental reaction -- that of flight. In order that an animal shall lie wholly motionless in the presence of danger, it is essential that this motionlessness shall be complete. Such danger would generally come from another animal and owing to the primitive character of the cognition of movement in visual perception, to which I have already referred, it is essential that the animal in danger shall avoid any movement whatever. There must be complete suppression of such impulses as would produce even a trace of the movements which make [p. 68] up the reaction by flight. Moreover, it is equally necessary that the consciousness of the animal reacting to danger by means of immobility shall not be disturbed by such feelings or images as would tend to set up movements, whether adapted to flight or of an irregular kind. It is essential that such consciousness as the animal may possess shall be wholly in harmony with the need for immobility which the instinct of the animal has led it to adopt. The need for suppression is all the greater in that animals which are accustomed to react to danger by immobility are usually, if not always, capable also of the reaction to danger by flight. We have not merely to do with an ancestral tendency to an incompatible kind of reaction, but with the need for the inhibition of an alternative mode of reaction. Moreover, there are many animals which flee till they have removed themselves from the source of danger, and only then resort to the reaction of immobility. In such a case it is necessary to inhibit a mode of reaction which, only a moment earlier, has been in full activity. The mechanism of suppression is thus one which must have come into being at a very early stage of animal existence. When, far later, an animal changed its habit of life, as in taking to an arboreal existence, it would already possess, waiting to be utilised when needed, a mechanism by which it could suppress instinctive impulses and conscious states which would interfere with the needs of its new life.
I have so far considered especially the needs for suppression which would be required when there is the possibility of two kinds of instinctive reaction incompatible with one another, or when an animal adapted to one kind of existence is forced by new needs to take up new modes of reaction which would be disturbed even by traces of its old behaviour. Still another opening for suppression is presented by those animals whose life-history is characterised by changes of habit so great that the modes of reaction proper to one phase could be seriously prejudiced if the tendencies of the earlier phase or phases were not suppressed. Thus, the metamorphoses of an insect produce existences so different from one another that if the impulsive [p. 69] tendencies and modes of consciousness proper to one phase were to continue in a later phase, they would greatly interfere with the behaviour proper to that phase. Thus, during the larval existence of the butterfly, the caterpillar reacts to the stimuli of certain leaves and plants in definite ways and exhibits certain movements adapted to the mode of progression proper to that stage of the life-history of the insect. If the impulses to such movements or the feelings and sensations which aroused the activity of the caterpillar were to persist in the imago, they could only interfere with the harmony of movements exquisitely adapted to the wholly different motions of flight. The harmony of its existence would be continually prejudiced if the memories of its larval existence were liable to intrude into the consciousness of the fully-developed butterfly with its vastly different needs and interests.
Again, to take an example from an animal nearer to ourselves, the movements of the frog could only be impaired if it were liable to be disturbed by impulses of such a kind as were needed by the tadpole, or if sensations referable to its caudal extremity were liable to complicate the sensations regulating the movements of limbs which did not exist in its larval stage.
I have so far spoken only of suppression of tendencies and conscious states as characters of early modes of animal reaction. In the case of Man, however, we have not only suppression of tendencies and of states of consciousness, but there is definite evidence that the suppressed experience and the tendencies I associated therewith, may have a kind of independent existence, and may act indirectly upon or modify consciousness even when incapable of recall by any of the ordinary processes of memory. Let us now inquire how far there is evidence of this continued existence in those animals in which we have found evidence for the process of suppression. One form of instinctive reaction, the suppression of which has been shown to be necessary under certain conditions, is that of flight, whether by movements of swimming in the water or of running upon the ground. Although these movements may need suppression, either in the interests of the alternative instinct of immobility [p. 70] or of a new mode of existence, the older instinct may still be needed at times. It is essential that its mechanism shall remain intact ready to be utilsed whenever it is needed. For most animals it is essential that the mechanism for each kind of reaction shall be present ready to be called into activity if the need should arise. This is so even if one mode of reaction is habitual, while the need for the other may only arise once in a lifetime or may always lie dormant.
The need for the continued existence in one phase of an instinctive mode of reaction proper to another phase of the life-history of an animal subject to metamorphosis is less obvious. There is no immediately obvious reason, for instance, why a butterfly should preserve among the potentialities of its existence the sensations or feelings which were aroused in the caterpillar by the leaves on which it feeds. One possible motive for such preservation, however, may be discerned. It is essential to the existence of the species that the female butterfly shall lay her eggs on or near the plant upon which the future larvæ will feed. In order that this shall happen it seems to be essential that the food-plant shall be capable of arousing such sensations in the butterfly as will make her choice possible. Professor Seligman has suggested to me that it may be to this end that the suppressed sensations of the larva persist during metamorphosis to be called once more into activity when, preparatory to its death, the imago carries out the act by which it perpetuates the race.
 See p. 58.