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tion of the impinging force; in other word, when the organism is oriented. The anterior end will be directed toward the source of the stimulating agent or away from it, according as it is the decrease or increase in intensity that is the effective stimulus'. The transference of the organism along the axis of progress has in these cases no effect on the relation of the organism to the stimulating agent, so that so far as this reaction is concerned backward progression might take place as well as forward. Under these stimuli a certain orientation of the organism, not a certain direction of progress, is the essential result of the reaction. This class of reactions forms the basis, so far as the infusoria are concerned, for taxis proper (MASSART, DAVENPORT, etc.), strophic taxis (ROTHERT), and topotaxis (PFEFFER).

Thus in the first class of reactions the essential result is a certain direction of progression—toward a region of greater or of less intensity--while in the second class the essential result is the orientation. But in both classes the nature of the stimulus is the same and the reaction is the same. The stimulus is some change in the relation of the organism to the surrounding conditions—a change in the intensity of action of some agent. The response is a motor reaction that consists of a series of trial movements. The response continues in each case until the effective stimulus comes to an end, then the usual motion is resumed. In the first class this does not produce orientation (save some times by "exclusion"), because stimulation comes to an end without it. In the second class it does produce orientation, because stimulation does not come to an end without it. The difference between the two classes depends on the peculiar difference in the distribution of the stimulating agent, not upon different ways of reacting on the part of the organism. The reaction is by "trial” movements continued till a cessation of the effective stimulation is brought about; this will lead to orientation or not, just as the conditions require.

H. S. JENNINGS.

"For details as to this relation, see this Journal, 14, 1904, pp. 470, 472, and 478 ; Carnegie Institution, Publication 16, 1904, p. 60.

THE PROBLEM OF INSTINCT.

In the whole field now awaiting the student of mental life in animals, there is nothing of more cardinal interest and importance, both for animal psychology in itself and for general psychology, than the group of problems centering about the development of the conative life. And of these problems none promise results so significant in themselves or so generally illuminative of the mechanism of mind, as the problem of instinct. The question of the origin of instincts ranks as a classic. Many prominent naturalists and psychologists have taken a distinctly anti-evolutional view of the matter, claiming intelligence and volition as the source of instincts. They make a good case; at least there are facts of introspection which point unmistakably in this direction. On the other hand, the facts at our com mand point to an evolution of mental processes as well as of physical structure. Instinct is clearly the conative life of lower forms. They seem to have no other conative life. Higher forms have both instinctive and intelligent conation. But it is still an open question whether the instinct is the result of the automatization of volitional processes, or whether it is the unconscious reaction which has been selected by the environment and is thus the precursor which prepares the way for volition.

The adaptation to the environment, through complex and yet very fundamental instincts, as well as the fact of habit formation in the individual life, make for the view that choice is a factor in the formation of instinct. On the other hand, the general order of evolution and development would place the simple, the instinct, before the more complicated volition. Volitions may be comparatively simple and instincts may be quite complex. But the general plan of the instinct marks it as an earlier form than the volition. We certainly have the indubitable evidence of introspection for this order in ontogenesis. And we see the same order in the mental development of the child. The same is true in the phylogenetic series; but the further we go from a ner

vous system like our own, the greater becomes the merely analogical element, and the less trust we can place in the inference.

But indisputable factual evidence can be brought to bear for the definite answering of this question of the origin of instinct-as to whether instinct in its simplest lines originates through the automatization of volitional acts or not. That is, we can obtain definite data concerning the functional and genetic relations of instinctive and volitional processes in animals which have both. The method we propose is simply this :Take an animal with well defined but comparatively simple instincts. Make a careful study of its instincts, both as they come forward in the growing animal and as they function in the adult animal: Then devise a set of experiments, for the express purpose of testing the intelligence of the adult animal, its power and capacity for dealing with new conditions. In this way it will be quite definitely ascertained whether the present intelligence is such as would have sufficed for the determination of the behavior of the same animal which now constitutes its instinct. For it is a reasonable and necessary assumption that if instinct arose thus through the automatization of volitional acts, the present intelligence of the animal should be equal to dealing as efficiently with similarly complex situations. For the function of automatization is not to do away with intelligence by rendering it useless, but to make possible its further advance by providing for the ready performance of that which has been learned already. This is the way it does work in our own development.

Of course great care and skill will be required in devising the experimental means of this test and in carrying them out. Such criticisms as those made by Professor Mills (Science, N.S., 191, 745.) of Dr. THORNDIKE in particular and of the laborators," as he calls them, in general, must be kept carefully in mind. We must assure ourselves in every possible way, as by checks and counter-checks and all possible variations, that the stimulus is acting upon the animal in the way that we think it is, that it is really attending in animal fashion to the situation as we are thinking the situation, and that it is really feeling the

impulses which we think it is feeling. In other words we must use every means to ascertain the mental factors of the situation before offering any interpretation of the meaning of the behavior, or using the observed behavior to strengthen any particular theory of psychic functional relations We cannot hope for absolute certainty of the processes in other minds by any known method, and the certainty is less the further we recede from our selves. But the careful student of the habits of the animal in its natural condition, by exercising care to have the animal in as nearly natural conditions as the experimental necessities admit of, and by being careful to isolate the experimental condi tions for the animal, will be able to interpret the movements and incipient movements in mental terms and thus have a close approximation to accuracy in grading the intelligence of the animal as shown in the particular situation. Accurate and detailed knowledge of the natural life of the animal, it cannot be insisted too strongly, is of the highest importance both for the proper planning of experiments and for the interpretation of the results.

If under these conditions it can be shown that an animal now has a grade of intelligence sufficiently high to serve as the guide in shaping any and all of the instinctive modes of behavior with which it is equipped, it has not been shown thereby, of course, that intelligence was the means of its development. The development of mind may have brought fourth this grade of intelligence at a later stage in the race history than that at which the instincts took their rise. In this case the results would be merely negative. If, though, it can be shown that a given animal has, as its mental equipment, an intelligence too low to deal with a situation as complex as that dealt with by the instinct, the inference is then clear that the instinct has come by some other way than by intelligence.

For our major premise, as before, is that intelligence as a whole never retrogrades, but when released through automatization proceeds to greater complexity and higher organization through dealing with more complex situations, This case would presuppose a retrograding and would therefore be impossible. And so it was not con

scious (I do not mean self-conscious) choice which determined originally the mode of reaction which is now instinctive.

This position being established, the way would then be open for the psychologist to construct and maintain a theory of the origin of volition and cognition as developing out of a system of organic behavior. This negative evidence, if it can be found, will contribute to a constructive theory of the systematic development of mind as a progress from the simpler and less organic to the higher and more organic. For intelligence is both of these as compared with instinct.

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