The Animal Mind: A Textbook of Comparative Psychology

That the prolonged period of human infancy is of advantage to the intellectual life of man because it means plasticity, the absence of fixed instincts that would take the place of acquisition by individual experience, was first pointed out by Fiske (227). But quite as important is the fact that in prolonged infancy we have the opportunity for acquiring the habit of that attention to our own movements which is the prerequisite for anticipated movements.

There are, as we have seen, various ways of learning by experience — slow ways that do not involve ideas, and the rapid way that does. The great advantage of man over most of the lower animals is not so much in the fact as in the method of his learning. One of the most vital meanings of the long period of helplessness and dependence constituting human infancy lies in the fact that by relieving from the necessity of attending exclusively to external objects, it renders possible attention to the sensations resulting from movement; and thus, by supplying an essential condition for the anticipated movements, it opens the way for the control of movement through ideas.

~§ 79. Some Alleged Instances of Remarkable Mental Powers in Animals All of the experimental evidence which we have examined indicates that even in the cleverest animals’ intellectual ability falls far short of that demonstrated by rather dull human beings. But a few years ago in Germany the hypothesis was advanced that the minds of such animals as horses and dogs are really quite on a par with those of human beings; their apparent deficiencies being due to the fact that we have never learned how to educate and communicate with animals. In 1901 a Berlin gentleman, Herr von Osten, began training a five-year old horse named Hans to answer arithmetical questions by tapping with his hoof on the ground. Taps with the right hoof meant units, taps with the left hoof meant tens. Later, an alphabetic system was constructed on a numerical chart: the letter a, for example, being found in the vertical column numbered 3 and the horizontal column numbered 2, tapping three times with the left hoof and twice with the right

meant a. Thus Hans was trained to answer questions other than those concerned with numbers. He showed ability to do so with seeming intelligence, and to work arithmetical problems. He was examined successively by two commissions, and a psychologist on the second commission, Pfungst, apparently solved the mystery of Hans’s behavior by showing that the person who put the questions to the horse made unintentionally a slight movement of the head when the proper number of taps had been given, and that when such movements were intentionally made, the horse responded to them. So the matter rested, with the simple solution that the horse had, instead of really thinking, merely reacted to involuntary signals. After the death of Herr von Osten, Hans came into the possession of Herr Krall, a business man of Elberfeld, who was not satisfied with Pfungst’s explanation, and besides continuing the education of Hans, trained several more horses, the most gifted of which were two Arabians named Muhammed and Zarif. In two weeks Muhammed learned to add and to subtract ; he passed in three days from multiplication and division to the use of fractions; he acquired remarkable skill in the extraction of square and cube roots, and finally he as well as his fellow pupil began to offer original observations. These performances occurred even when the horses were prevented from seeing anyone. Much the same sort of phenomena are reported in the case of Rolf, the Mannheim dog. The most recent reports of the Elberfeld horses are less enthusiastic, and even claim fraud, although not on the part of Herr Krall, whose disinterestedness seems accepted. It is impossible to determine just what cues are responded to by these animals in their performances, but aside from all the negative weight of the evidence obtained under exact experimental conditions on

other animals (it will be recalled that the horse was the stupidest of all Hamilton’s subjects), certain indications point clearly away from the possibility that the horses are really mathematical geniuses. (1) They learn too quickly to allow of their understanding. A gifted human being could not acquire so fast a, real apprehension of mathematical relationships. (2) They take no longer for hard problems than for easy ones. (3) They begin tapping without even glancing at the problem written on the board. (4) The character of the mistakes they make is not that of the mistakes of a real calculator: very common errors are reversals of the figures, thus 27 for 72, or errors of one unit, as 21 instead of 22. These are errors which might easily be made if the two forefeet were confused in the tapping, or if the tapping stopped a little too soon or not quite soon enough. They are not real arithmetical errors, such as forgetting to carry a figure over from one column to another, for instance. 30) No really satisfactory results have been reported when no one present knew the correct answer. On the whole, the phenomena do not present themselves with such authority as to compel a revision of our whole conception of the animal mind (125,

We may conclude our study of the modification of conscious processes by individual experience with a brief summary of some incidental factors which affect the learning process. (1) The age of the animal has an influence upon its ability to learn. Watson (766) compared the ability of young white rats with that of mature animals in the learning of puzzle-box and maze habits. He was especially interested in testing Flechsig’s theory that learning depends upon the presence of medullated fibres in the central nervous system. The theory was unconfirmed, for such medullation is highly imperfect in the rat at twentyfour days of age, yet at this age Watson’s rats learned a labyrinth more quickly than did the adults. The rat belongs to the class of animals that are born unable to care for themselves, and before those observed by Watson had reached the age of twelve days, they were unable to find their way by a simple maze path back to the mother. The superiority of young rats over adults in learning a maze path is apparently due to their greater activity; they make more useless movements, and in solving a puzzle box they are at a disadvantage as compared with their elders.

Allen’s (4) work on the guinea pig was intended for comparison with Watson’s study, because the guinea pig comes into the world, not helpless like the baby rat, but well equipped on both the sensory and motor sides. In the labyrinth tests the mother was put at the end of the maze, and the sight and smell of her were supposed to serve as the stimulus to activity. Before the young animals reached the age of two days they did not succeed in learning a comparatively simple path, but at that age they did learn it, and proved the fact when the wire netting box in which they were placed was turned about, by pushing at the place where the opening had been. At three days they learned a more complex maze, and appeared to possess the ~ learning capacity of adults.

Yerkes (821) found that the dancing mouse at one month old learns a black-white discrimination faster than an older mouse. From one to seven months of age there is a decrease in learning speed; from seven to ten months, an increase. The power to discriminate appears to be better in younger mice; the power to associate better in oldet ones. Thus the superiority of the younger animals is rather in speed of sense perception and movement than in real learning ability.

Hubbert (345) has confirmed the statement that young rats learn the maze more rapidly than older ones. Moreover, she finds that in the younger animals, the most rapid stage of the learning occurs at an earlier point. (2) The sex of the learner may have some effect on the learning, although no very definite differences have thus far appeared. Yerkes (821) reports that young male dancing mice learn faster than females, and that females from four to ten months of age learn faster than males. Hubbert (345) states that except in the cases of very young and very old rats, males learn more readily than females ; the absolute time of running the maze is however shorter for females.

(3) The number of trials a day affects the speed of the learning. Yerkes (820) found that the dancing mouse learned a white-black discrimination in fewer trials the smaller the number of trials a day. Ulrich (738) has shown that the white rat learns a puzzle-box habit or a maze habit in fewer trials if one trial is given a day than it requires if either three or five trials are given a day. Apparently even better results are secured by one trial every third day. The same principle appeared to hold when several problems were being learned at once. This principle, . known as that of distributed repetitions, has long been recognized in human memorizing, although we do not know the explanation for it. But-learning is always more economically secured if intervals of time-are allowed to elapse between. repetitions.

acquisition of other habits. Yerkes’ (820) reports that dancing mice which have learned one maze learn another one more readily than those which have had no previous training. Richardson (634) finds previous experience a help also to the rat: experienced animals were more susceptible to stimuli and showed better codrdination of their activities. Hunter (349), on the other hand, found that pigeons which had learned one maze were delayed in learning a second one, and Yoakum (832) reports a similar condition in the learning of puzzle-boxes by squirrels: the older habits interfere with the acquisition of the newer ones. Hunter and Yarbrough (355) conclude from experiments on establishing auditory associations in white rats that a formed habit interferes with the formation of a new one, but that the new habit does not react unfavorably upon the old one. This has been found true of human memorizing also. Probably, when an animal seems to learn a new habit better because of having previously formed a different habit, the advantage is merely in the fact that it has become used to being experimented upon, to the experimental situation. (5) The differences in individual ability among animals are marked. We are inclined to think of all the animals of a certain species, especially if it be a species far removed from man, as equally gifted, but it is quite possible that among ants and earthworms there are geniuses and dunces. Turner (729, 730) reports striking individual variations in the behavior of cockroaches learning a maze; two of the rats tested by Small (685) with puzzle-boxes never learned to get into the boxes, but merely profited by the activity of their more -gifted companions. Wodsedalek_ (795) gives a delightful account of a specially talented Mayfly. Practically every experimenter reports similar individual variations.

THE student absorbed in reading ‘“‘does not hear” an approaching footstep. That is, a stimulus which would under other circumstances produce an effect loses a great part of its influence because of the fact that another stimulus is already upon the field. This other stimulus need not be more intense, that is, need not involve more physical energy, than the one which is ignored. It does not win the victory by a mere swamping of its rival through its superior quantity. Aman may walk along city streets, his eyes and ears bombarded with brilliant lights and loud sounds, and yet the centre of his consciousness may be a train of ideas, representing in their physical accompaniment in his cortex a quantity of energy insignificant compared with that of the external stimuli pouring in upon him. Psychologists commonly express this fact by saying that while the strength of a stimulus conditions the intensity of the mental process accompanying it, the clearness of that process depends upon atiention.

Attention, then, is the name given to a device, whatever its nature, whereby one stimulus has its effectiveness increased over that of another whose physical energy may be greater. What happens in the simpler forms of animal life when two stimuli, requiring different reactions, operate simultaneously? We may quote from Jennings the facts about Paramecium. “If the animal is at rest against a mass of vegetable matter or a bit of paper, . . . and it is then struck with the tip of a glass rod, we find that at first it may not react to the latter stimulus at all.” “A strong blow on the anterior end causes the animal to leave the solid and give the typical avoiding reaction.” ‘If specimens showing the contact reaction are heated, it is found that they do not react to the heat until a higher temperature is reached than that necessary to cause a definite reaction in free-swimming specimens.” ‘‘On the other hand, both heat and cold interfere with the contact reaction. Paramecia much above or much below the usual temperature do not settle against solids with which they come in contact, but respond instead by a pronounced avoiding reaction.” ‘‘Specimens in contact with a solid react less readily to chemicals than do free specimens. ... On the other hand, immersion in strong chemicals prevents the positive contact reaction.” “The contact reaction may completely prevent the reaction to gravity,” and to water currents. It also modifies the reaction to the electric current. While a part of the influence exerted by the contact reaction on other responses may be purely physical, due to the fact that an actual secretion of mucus may occur whereby the animal “‘sticks fast” to the solid, yet this alone does not explain the facts, for the cilia that are not attached do not behave normally. The reaction to gravity regularly yields whenever opposed to the action of any other stimulus (378, pp. 92 ff.). Sometimes the action of one form of stimulation merely affects the form of the response to another, as in the case where abnormal temperature causes the avoiding instead of the positive reaction to be given to solids.

In other cases, reaction to one of the stimuli is suppressed or weakened. The facts suggest that the influential stimulus is either the one that is on the field first (the contact reaction may prevent response to temperature, or abnormal temperature may modify the contact reaction), or the one that is the more important (gravity yields always to other stimuli). In some higher animals the effects of interference of _ stimuli have been noted. The earthworm will not respond to light if feeding (171) or mating (327). In the turbellarian Convoluta roscoffensis light is victorious over heat in determining reaction. The animals in their positively phototropic phase will remain in the heated light end of a vessel until they perish. Light and gravity are more nearly balanced in their effects. Convoluta is negatively geotropic, yet if the brightest region is below the surface, the animals will go there. But if this region is only a little brighter than the surface, they will stay at the surface, gravity dominating (253). The sea-urchin shows in its behavior a somewhat similar relation between mechanical and chemical stimulation. If weak acid is dropped into the water containing specimens of Arbacia, their spines begin to interlace. A slight shaking will restore them to the normal position, but if more acid be added, no mechanical stimulation will overcome the effect of the chemical (734). Various facts concerning the interrelations of gravity and light as stimuli have been noted in Chapter IX. A very interesting case of the suppression of one reaction by another is reported by Holmes in his observations on the water insect Ranatra. The positive response of this insect to light, very precise and striking, may be wholly suspended when the animal is feeding, when a number of individuals are collected, when the insect stops to clean itself, or even ‘‘by the sudden appearance of a large object in the field of vision,” behavior which is strongly

suggestive of the “distraction of attention” in a human being (335). Holmes (337) also observed that the fiddler crab, although it ordinarily moves towards the light, would run away from a moving light, fear overcoming positive phototropism. Roubaud, in a study of the behavior of some species of flies that live on the seashore, feeding on dead fish and the like, says that they will abandon the “head on” position which they regularly assume toward the wind, if attracted by the odor of food (646).

Wherever we find that one class of stimuli regularly yields to another if the two act together, it is safe to assume that the prepotent stimulus is more important to the organism’s welfare than the vanquished one. And while we cannot without more ado call such cases of the interference of stimuli as are found in very simple animals cases of attention, and ascribe to their psychic accompaniment all the characteristics of attention as a feature of our own expe- ' rience, yet we may assert that they have in common with attention the significance of being a device to secure reaction to the most vitally important of several stimuli acting at once upon the organism.

§ 82. Methods of securing Prepotency of vitally Important Stimuli An inanimate object acted upon by several forces at once is determined in its motion by their relative intensity. Conceivably, an extremely simple form of animal life, when subjected to two stimulations acting together, would also respond in a way answering precisely to the relative strength ofthetwo. Itis easy to see what would be the disadvantage of such a state of affairs for the animal. The weaker of the two stimuli might be of far greater significance for

organic welfare than the stronger. For example, it would often be important that an animal should be able to respond to a very faint food stimulus rather than to any of the stronger forces acting upon it. Evidently a prime need of animal life is some arrangement whereby weak but important stimuli shall be given the preference in determining reaction over stronger but less vitally necessary ones. Sense organs are one such device. The comparatively slight’ amount of chemical energy coming from a bit of food may have its effectiveness for the nervous system greatly increased through its reception by a structure adapted to use the whole of it to advantage. Light stimulation involves a quantity of energy that is insignificant in comparison with the grosser forces acting on an organism ; yet falling on the retina, the energy is economized and magnified through the stored-up chemical forces it sets free. Thus a weak stimulus may by a sense organ be made powerful to determine reaction. Another arrangement to the same effect is the peculiarity of the nervous system whereby, through an arrangement akin to the summation of faint stimuli, @ moving stimulus, one acting successively upon neighboring points of a sensitive surface, produces an effect disproportionate to its intensity. A moving stimulus is a vitally important stimulus; it means life, and hence may mean food or danger. The response to it is in most cases adapted rather to its importance than to its physical strength. A third arrangement for the securing of reaction ‘to vitally important stimulation lies in the existence of preformed connections in the nervous system, which bring it about that the path of the excitation produced by one stimulus is clear to the motor apparatus, while that of another is closed. Reactions of this sort we call instinctive.

The nesting bird responds to the sight of building material rather than to that of objects offering equally strong stimulation to the optic nerve; the cat sits at the mouse hole, the parent animal responds to the faintest cry of the offspring, because these stimuli have the right of way by virtue of inherited nervous. connections. Finally, a weak stimulus may determine reaction and be victorious over a stronger one because of nervous pathways formed through the individual’s own experience. ‘The consequences of reaction to it in the individual’s past may operate to secure reaction to it in the future. To the cat in a puzzle box, the string that must be pulled to let it out offered originally no stronger stimulus to action than any other object in sight; but after sufficient experience the string comes to dominate the situation and determine the cat’s behavior. If the experience of consequences is slowly acquired, by many repetitions, the process of reacting to an object originally indifferent may be unaccompanied by any ideas of the consequences of such reaction. If it is rapidly acquired, we know that we human beings at least accompany our reactions by calling up the results of our past reactions in the form of memory ideas.

§ 83. The Peculiar Characteristics of Attention as a Device to Secure Prepotency We have suggested that attention is a means of securing reaction to the vitally important stimuli acting upon an organism. Does reaction to a stimulus always mean attention to the sensation accompanying that stimulus? This question may best be answered by examining the characteristics of the attention process as we know it. In attention, the details of the object attended to become clear and distinct. Thatis, attention is a state where discrimina-

tion is improved. Further, attention involves varying degrees of effort, and these are marked by varying intensity of certain bodily processes. Attention under difficulties is accompanied by a rigid position of the body, by holding the breath, and by various muscular effects, aside from the processes which, like frowning, are concerned with the adaptation of the sense organ to receive an impression. These general bodily effects of attention are all such as to suggest that the body is to be kept as quiet as possible during the attentive state. In other words, no reaction is to be made to the object attended to except such as may be necessary to allow its being carefully discriminated from other objects. Aitention, in its intenser degrees, at least, seems to involve a state of suspended reaction.

Not every case, then, of response adapted to the vital importance of a stimulus is a case that suggests as its psychic aspect attention to the accompanying sensation. When, for example, a reaction of especial speed is made to contact with a moving stimulus, the speed of the reaction would itself indicate that the sensations produced are not attended to. The proper situation for attention would be the situation in which the reaction needs to be suspended until the stimulus is fully discriminated. Now such careful discrimination does not appear to be characteristic of reactions that are largely based on inherited nervous structures. Many facts concerning the instincts of animals, that is, their inherited reactions, indicate that these are extremely rough adjustments of behavior to environment until refined by individual experience. Hudson observed, for example, that newly born lambs on the South American plains had a tendency to run away from any object that approached them, and to follow any object that receded from them. They would follow his horse for miles as he rode along, and would run

away from their own mothers when the latter moved toward them. He explained this as adapted to the fact that ordinarily their first duty, on making their appearance in the world, is to keep up with the receding herd, while an approaching object is more likely to be an enemy (347). Later, this rough adjustment is modified; they learn by experience not to run away from their mothers, and not to follow indiscriminately any leader. If it is true that instinct unmodified by experience is adapted to general rather than to special features of environment, it seems likely that the phenomena of attention as we know them are found chiefly in connection with those responses to vitally important stimulation which are determined, in part, at least, by the individual experience of the reacting animal, for these are the responses requiring most careful discrimination among stimuli, and the delay of reaction until such discrimination has been made.! Putting the matter in a slightly different way, we may say that purely inherited responses can be adapted only to certain broad, roughly distinguished classes of stimuli, for these alone are common to the experience of all members of the species. Nothing but individual experience can bring to light the importance for welfare of certain particular stimuli, for the significance of these would vary with the experience of each individual animal. Among the lower animals, attention probably reaches its highest pitch where the response most needs to be suspended in order that the

1In this connection Franz’s experimental demonstration that the frontal lobes, long regarded as the seat of the neural processes underlying attention, are concerned in the functioning of recently learned reactions, is of especial interest. Franz found that cats and monkeys which had been trained to work mechanisms lost the power to do so when the frontal lobes were extirpated, although habits of older date, such as responding to a call, were preserved (237, 238).

stimulus may be fully discriminated. The rabbit or wild bird crouching motionless close to the ground, watching each movement of a possible enemy, suggests strongly to our minds a condition of breathless attention. Whether such an interpretation is the true one depends very much, I should say, on the extent to which past individual experience has refined the animal’s powers of discrimination. Mere “‘freezing to the spot”? may be an inherited reaction, useful in time of danger, but more analogous in its psychic aspect to the blank emptiness of the hypnotic trance than to alert, watchful attention.

Yet although, in so far as attention is a state favoring discrimination of stimuli, it is involved in that part of an _ animal’s behavior which is derived from individual expe- - rience, since pure instinct discriminates but roughly; in so far as it is still one of the devices for securing reaction to stimuli of vital importance, its root must lie in instinct. No object wholly unrelated to some fundamental instinct can hope to secure attention, for the great classes of vitally important stimuli have all of them preformed paths in the nervous system by which their reactions are secured. What individual experience does is to refine upon the adaptations which instinct makes possible; to bring about the connection of certain stimuli, originally indifferent, with the performance of an instinctive response, or to produce a checking of the instinctive response when certain individual peculiarities of a stimulus that would otherwise call it forth become evident. For instance, an animal learns by experience to come at the call of a human being who feeds it; the sound, originally without effect on its reactions, has come to be connected with the nervous mechanism of an instinct. The chick pecking at small objects on the ground

learns by experience to inhibit this instinctive response with reference to objects having certain peculiarities originally undiscriminated, but now in some way emphasized through painful circumstances accompanying his previous encounter with them. The most fundamental characteristic of attention, then, is perhaps that aspect of it which has been called abstraction, the diminished effectiveness of stimuli not attended to. By virtue of this aspect we recognize that attention belongs with instinct as being concerned in securing the prepotency of vitally important stimulation. On the other hand, the further characteristic of attention ; namely, that it is a state of suspended reaction involving careful discrimination of stimuli, suggests that its functioning is connected rather with the refining and modifying influence of individual experience acting on instinct, since here alone do we find delayed reaction and accurate stimulus discrimination.

The highest grade of attention, the final triumph of vital importance over mere intensity of stimulation, is to be found where the focus of attention is occupied by an idea or train of ideas. When a process purely centrally excited holds the field and makes the individual deaf and blind to powerful external stimuli pouring in upon his sense organs, then he is superior to the immediate environment at least. This form of attention occurs, probably, only when the vital importance of the idea attended to has been learned through that most rapid form of individual acquisition of experience which involves the revival of the past in idea. It has been called derived attention. The ideas attended to are held in the focus of consciousness and analyzed through the power of associated ideas. The inventor holds to his problem, the student to his task, in spite of distractions, because of the consequences which he thinks of as likely to result. It seems unlikely that attention in this final form occurs among

the lower animals. While ideas are probably present to some extent in the minds of the higher mammals, they are hardly so far freed from connection with external stimuli that the animal can shut out the world of sense from its consciousness and dwell in a world of ideas. The following is a list of the books and articles consulted in the preparation of this work. Not all of them are cited in the text. Apams, G. P., 1903. On the negative and positive phototropism of the earthworm, Allolobophora fetida, as determined by light of different intensities. Am. Jour. Physiol., vol. 9, p. 26.

Krafte bei den Bewegungen niederer Organismen. Jena. Zeitschr. f. Naturwiss., Bd. 22, S. 310. . ALLABACH, D. F., 1905. Some points regarding the behavior of ANDREAE, E., 1903. Inwiefern werden Insekten durch Farbe und Duft der Blumen angezogen? Beihefte z. botan. Zent., Bd. 15, S. 427. AXENFELD, D., 1896. Die Réntgenschen Strahlen dem Insektenauge sichtbar. Cent. f. Physiol., Bd. 10, S. 436. 1899. Quelques observations sur la vue des arthropodes.