W.H.R.Rivers

“ It is characteristic of emotion that it flares up at once and leads immediately to the behaviour characteristic of it. When, on the other hand, the crude affective tendencies which I associate with instinct have been brought under control, and even brief reflexion becomes possible, the emotion will only come into being if the conditions tending to produce it have such force as to sweep before them with their flood the obstacles interposed by intelligence. ”

“ A third and most important distinction which has been made between instinct and intelligence is that the former is innate and the latter acquired. If an animal or man behaves in a way which is quite independent of any experience it can have acquired in its individual existence, the behaviour is regarded as purely instinctive. if, on the other hand, it were possible to say that the behaviour of an animal or man was wholly determined by the experience of the individual, we should regard the behaviour as an example of pure intelligence. ”

“ The optic thalamus is now hidden sway in the interior of the brain, overlaid and buried by the vast development of the cerebral cortex. Just as I have supposed that emotive and instinctive reactions are buried within the unconscious, hidden from consciousness by the vast development of those reactions which are associated with intelligence, so do we find that the organ of the emotions and instinctive reactions has been buried under the overwhelming mass of the nervous structure we know to be pre-eminently associated with consciousness. ”

“ The "all-or-none" principle may be regarded as only a special case of a wider law holding good of the relation between stimulus and sensation, or between stimulus and reaction. Except at the limits of the range of intensities the normal sensibility of the skin or other sense-organs shows definite proportionality between stimulus and reaction, of which the most exact expression is given by Fechner's formula that the sensation is proportional to the logarithm of the stimulus. ”

“ Nevertheless in the present state of the subject I believe we shall do best to take as the distinguishing mark of instinct its innate character, even though this character be biological rather than psychological. We shall do best if we devote our inquiries to the attempt to distinguish different kinds of instinct according to their psychological character. It should be our task to analyse the general group of instincts into its component parts just as it has been the main task of psychologists hitherto to analyse the different forms of intelligent behaviour. ”

“ In the last chapter I have adopted the current view that such emotions as fear or anger, with the reactions characteristic of them, are expressions of instinct. When they occur in Man, these reactions are prominent, even the most prominent, elements in that part of his behaviour which can be ascribed to instinct. ”

“ In the case of the animal the movement of a shadow thrown by a falling leaf may produce as strong a reaction as the full sight of its deadliest enemy. The child may scream as vigorously after some trivial touch as it does with the pain of a cut or burn. ”

“ The characters which I have used as a means of distinguishing the instincts which are especially obvious in the innate behaviour of Man resemble in many respects the characters of protopathic sensibility, of a person who is dependent on the activity of the thalamus or of the isolated spinal cord, and in the domain of pure physiology the characters of the isolated nerve and of the heart. ”

“ In the higher vertebrates, i.e., in those which have developed a cerebral cortex or neo-pallium as part of their central nervous system, instinct is regarded as the product of sub-cortical activity, while intelligence is held to depend on the activity of the cortex or neo-palium. ”

“ Any such exact relation is wholly absent in the case of protopathic sensibility, in the reactions of the "extensor-thrust" or the mass-reflex, and similarly, there is no such exact relation between the conditions setting an instinctive or emotional reaction into being and the strength of the reaction, at any rate in the child, or in the adult human being whose emotions have not been brought well under control by long training and practice. ”

“ When a weak electrical stimulus is applied to isolated nerve-fibre, and the impulse which in consequence travels along the nerve is measured, it is found that if the stimulus is weak there is no impulse at all, or more correctly, the electrical behaviour of the nerve gives no evidence of any impulse. If strength of the electrical stimulus is gradually increased, a point is reached when the nerve gives the response normally associated with an impulse passing along its length. ”

“ The distinction is one which is difficult to utilise in practice, for, as soon as an animal has acquired experience of any kind, it becomes a matter of the greatest difficulty to distinguish between the innate and the acquired conditions, while, as already pointed out, in all [p. 42] examples of intelligent behaviour, it is impossible to exclude innate factors. Often, as in the case of insects and other animals which carry out actions of a most complicated kind, wholly independent of individual experience, the distinction is valid and useful. ”

“ This difference between instinct and intelligence is one of great value and probably furnishes the best theoretical distinction between the two kinds of behaviour, but when we endeavour to use the theoretical difference as a guide in practice and research, we are met by several difficulties. ”

“ When a region of the skin which is endowed only with protopathic sensibility is stimulated with cold, the intensity of the cold sensation is roughly the same whether the temperature of the stimulating surface is zero or 20°C., i.e., whether it is the temperature of ice or about the temperature of a summer day. ”

“ It is not long since it was regarded as a sufficient definition of instinct that it is the mode of mental activity proper to animals as distinguished from the intelligence which was believed to be the chief, or even the only, factor of any importance in regulating Man's behaviour. All recent work in psychology 'has shown this distinction to be of little value. ”

“ In what I have just said I have spoken of the child as tending to scream and of the animal as tending to run away with all the force at their command, because I wish to make clear that the child or animal does not always behave in this thoroughgoing manner. ”

“ A gift of half-a-crown will have a very different effect on a beggar and on a millionaire, and it has been supposed that this relation is subject to logarithmic expression; that equal increment of good fortune produce steadily decreasing increments of pleasure. ”

“ He will devote every particle of his energy to flight or other form of primitive or instinctive behaviour. Thus, if he becomes angry and assumes an aggressive attitude, his anger and aggression will go far beyond those called for by the needs of the situation. ”

“ Similarly, it is characteristic of the reactions of protopathic sensibility that they tend immediately to result in movements approaching in nature those of reflex action, and are quite beyond the control which we normally exert over our more reasoned movements. ”

“ Even if this law could be shown to apply with any degree of exactness, it conceals a highly-developed aspect of the affective life, one in which the crude emotional basis has been elaborated by the addition of highly complex intellectual factors. The states of pleasure and displeasure, at any rate in their more customary forms, are definitely graded. ”