An Introduction to Comparative Psychology

Chapter 10: The Sense-Experience of Animals

C. Lloyd Morgan

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THE sense-experience, or consentience, as it has been termed, which results from the correlation of sense-data, forms the foundation of our psychical life; and it can hardly be questioned that it forms the foundation of the psychical life of animals. . There is scarcely anything, that has been said in the last two chapters which we may not fairly infer to apply in principle to those vertebrate animals, and especially the higher vertebrates, to which I have thought it best to confine our attention in this work. But when we go beyond these limits, when, for example, we attempt to interpret the psychology of insects, we find ourselves in face of serious difficulties, the nature of which may be indicated in passing, that my reason for restricting our zoological field may be made clearer.

Throughout our considerations the leading position taken by visual impressions has been obvious. Our world of practical experience is largely interpreted in visual terms. The retina of the vertebrate eye is so constructed that there is a small central area of maximum delicacy, the image or portion of an image which falls within this being for us, and we may infer for other vertebrates, focal. In other vertebrates as in us there is a mechanism for accommodation; while some other vertebrates, though only same, like ourselves use the two eyes in binocular vision. In all the vertebrates, with which we are dealing, there are muscles which allow of delicately-graded movements of the eyes in their sockets. Hence we may infer that what we learnt concerning the

(158) correlations in vision, and the correlations of movements in the visual field with the motor-sensations which accompany the movements of the eyes in their sockets, holds good for vertebrates as for men. But when we pass to the insect, the bee, for example, -- there are two kinds of eyes, the small simple ocelli, and the pair of large many-facetted eyes. There is no mechanism for accommodation in either; no movements of the eyes in their sockets in either. It is not improbable that the ocelli serve mainly the purpose of directing the insect to a glimmer of light, the opening of the nest, for example; while the method of vision in the many-facetted eyes, the so-called mosaic vision, is quite different from anything of which we have or can have experience. In the visual experience of the bee, motor-sensations, special to the act of vision, can take no part. But we have seen that these motor-sensations in association and correlation with retinal sensations make our visual experience what it is. Does it not, therefore, logically follow that the visual experience of the bee must differ so widely from our own, that our wisest course is an honest confession of ignorance? Is not the bee in this respect like the kitchen clock; and are not we chronometers which only know the nature of their own- insides? How little we know about the auditory and olfactory organs of insects; and what can we know at all about their auditory and olfactory experience? What know we concerning the tactile and other antennary sensations of the bee? What concerning the motor- sensations in that delicate organ ? Still more, what concerning the synthetic correlation of the data of antennary senses and of antennary motor-sensations ? In us the motor sensations in the limbs are largely due to the movements of joints in their sockets; to some extent due to tensions in a soft and delicate skin. But in the bee the skin forms a firm encrusting armour, except at the joints; the muscles of the limbs lie within the tubular armour, and the joints are very different from ours. In us, the mem-

(159) -branous labyrinth and semicircular canals give sensations accompanying changes in the direction or amount of move ment in the head and body generally. We do not know of anything of the sort in the bees. If then the tactual field must be somewhat different from ours, the visual field widely different, and the antennary field -not improbably the dominant factor in bee-experierice -- quite unknown, must not one infer that the nature of the sense-experience of this insect is a secret she keeps to herself, even if she be philosopher enough to fancy she has guessed it? And if senseexperience be the foundation of the psychical life, that upon which the superstructure of higher psychical faculty is based, how far are our conjectures concerning the bee-superstructure likely to be correct, if we are almost wholly ignorant of the nature of the bee-foundation ? Therefore, I say, let us not abate one jot of our industry in the objective -study of the habits and activities of the invertebrate animals ; but let us not pretend to know anything but the vaguest generalities concerning their psychology.

To return to the vertebrates ; it appears to me that with regard to them, or in any case the more highly organised among their number, we are justified in inferring that the foundation in sense-experience is of like nature to that in man. No doubt there are differences, and not unimportant differences, in detail. There can be no question, for example, that in the dog and the deer the olfactory field is of far greater practical importance than it is with us. I have lately made experiments with a fox-terrier to illustrate the way in which he practically utilizes the sense of scent. On the steep slope of a hill where limestone fragments from the rocks above have collected in considerable quantities among may-bushes, nut-trees, and other vegetation, I have watched him search for the stones I have pitched down for him to fetch. Selecting a spot where a little rising ground effectually prevented him from seeing where the stone fell, I have

(160) sent him after marked limestone fragments. Ile watches the initial direction in which the stone is flying, and then races off. After that he trusts almost entirely to scent, though I am inclined to think that the sound of the fall of the stone gives him some guidance as to distance. He then works the ground to and fro and backwards and forwards by scent; not by any means very systematically, for, he often goes over the same ground again and again. When the marked stone has merely been handled by me, he apparently scents it as soon as he comes within about a foot of it. But when he has brought it up in his mouth, and I throw it down again, he finds it much sooner, and scents it at a distance of about four feet. At this distance also he appears to sense the direction of the stone, for he turns rapidly and pounces upon it. In one set of experiments I sent him down again and again after a marked stone, pitching it down a hundred feet or so among, the bushes directly he returned with it. He thus brought it back thirteen times in twenty minutes in broad day light, and eleven times in the same period on a moonlit night, the side of the hill being in shadow. So completely does he rely upon scent, that I cannot readily get him to fetch a stone by sight. If I flick a stone down with my stick on to a heap of talus well within his sight, so that I can, and he could, see where it fell, he goes smelling over the heap, but fails to bring the stone. But if I set a stone rolling down with my stick, so that he follows it as it rolls, then he follows it by sight and brings it to me. There can be little doubt that sense-data of olfactory origin, in many animals, take a more prominent position in the organization of sense-experience than they do in man.

In the case of those animals -- like the rabbit, for example -where the eyes are so situated that they cannot combine in binocular vision, one must suppose that the image which falls upon the most sensitive area, or yellow spot, of one eye, suggests the focal impression; while that which falls on the

(161) similar spot in the other eye is marginal to its conscious consentience. In them the binocular factor in sensing distance must be absent, and distance must be sensed through the synthetic correlation of retinal impulses and motor impulses of monocular accommodation. This is how the man who has lost one eye senses visual distance, aided of course by suggestions of relative size, the effects of haze, and other such representative factors. It is certain that the binocular factor is not essential for the sensing of distance, for the chick, in which this factor is absent, soon strikes with great accuracy at a minute object. Still it is probably a great advantage. If you hold a chameleon on your finger near a fly, within striking distance with his long and flexible tongue, he never strikes till both eyes converge upon the insect. The tip of the tongue is practically shot out like a projectile, and the accuracy of correlation of sense-data, and co-ordination of motor impulses for the innervation of the muscles, are alike remarkable.

Nothing is more admirable than the skill of animals. One may watch by the hour with ever renewed delight the marvellously delicate adjustments involved in the sailing flight of sea-gulls. I once saw at the Cape a seabird chasing another that had secured a fish. Hard-pressed the .smaller bird dropped its prey, and with a swoop the other caught it in the air and sailed off with its stolen meal. An American observer, Mr J. Lancaster, describes in the American Naturalist[1] the following scene. "A fine specimen of the fish-hawk swooped on a fish, which soon left its native element and- swung aloft in the bird's talons. The hawk began its homeward journey. But now a new comer appeared upon the scene. A black creature, which seemed all wings, dropped from above and confronted the hawk, which at once let go its prey and uttered a scream so

(162) brimful of mortal terror as to excite one's pity. The hawk was not struck, and it made off in wild haste for shore. The intruder was a frigate-bird, which seized the dropped fish in, its beak long ere the prey reached the water, and then, with a sweep of exquisite grace, on tense wings, fronting a mild breeze, the corsair was lifted half a mile into the air. A bite was taken from the fish by a wringing motion of the bird's head, which sent the carcass whirling. The morsel being swallowed, the bird, folding its wings tightly to its body, dropped swiftly after the fish, seized it, again swept upwards, and then the performance was repeated till the meal was over," Every motion of birds in their flight is full of exquisite skill. Watch the swirlings of the swifts in the summer air; hundreds of insects, invisible to you, are being seized in a flight that is estimated at not less than a hundred miles an hour. Many of my readers must have watched at the zoological gardens, the skill with which the darter or snake-bird (Plotus) pursues fish, and captures them beneath the water, in the large tank at the end of the fish-house, or the skill with which the sea-lion catches the morsels which the keeper throws him. I watched the other day the unfailing accuracy with which an Irish terrier followed, and invariably caught at full-speed, a ball which his master flung for him across the open down; and I admired it all the more because I bad been teaching a fox-terrier to do this, and knew that such skill is not to be acquired in a day or a week. One of the most striking examples of combined intelligence and skill, and one which is rendered more striking by contrast, is the way in which a sheep-dog works the relatively unintelligent sheep on a steep and broken mountain-slope. Whether we regard the natural skill of wild animals, or the skill domesticated animals display under human guidance and for the service of man, we cannot fail to admire, if not to wonder. And since this skill is unquestionably a matter of sense

(163) experience, it will be well to consider carefully its psychological aspects.

In the first place it should be noticed that although, as we shall see more clearly in the next two chapters, skill is displayed in virtue of the possession of an organic mechanism which is inherited, and although the performance of all the essential activities is founded on a basis of an innate automatism, yet all the accurate finish and final touches of perfection are the result of individual acquisition. And it should he further noticed that this individual acquisition is something more than and something other than the increased smoothness of working of a piece of automatic mechanism. A new machine works better after it has been running for a while ; but the perfecting of animal skill is something more than this. I would ask anyone who is inclined to doubt this, and to regard animal activity as perfected automatism, to teach a dog to race after and catch a ball as it flies and bounds over a lawn. He will, if I mistake not, be forced to conclude that the "individual acquisition of skill through practice is not merely an increase in the smoothness of working of the automatic mechanism, but involves a delicate power of control over the motor apparatus. If we call this perfected automatism, we should remember that the automaton is one which profits by experience. And it is well to bear in mind that the words "automaton " and " automatic " are used in two somewhat different senses. An automaton is defined as "a self-moving machine," and automatic as " having the power of moving itself." If now we lay stress on the self-moving, we have one sense in which the word is used. In this sense I am quite prepared to regard myself and animals as conscious automata. But if stress be laid on the machine, then the word automatic acquires the connotation of mechanical uniformity of action. In this sense I do not regard myself and animals as automata. It is not for me

(164) to decide between these two uses. I shall, however, myself in this book use the words 11 automaton " and " automatic " in the se rise in which they imply mechanical uniformity of response, I shall speak in the next chapter of the just hatched chick as a little automaton, meaning thereby that in virtue of its organic mechanism it responds like an accurately made and nicely contrived machine to certain stimuli. And I shall use the word "automatism" in antithesis to control. The automatic act may be accompanied by consciousness, but the controlled act is guided by consciousness. And I think there can be no question that the perfecting of an act of skill is under the guidance and control of consciousness.

There are two factors in the perfecting of skill, -- the one is the nice correlation of sensory data; the other is the coordination of motor impulses or of muscular adjustments. The delicacy of this co-ordination, itself dependent on a like delicacy of correlation of sensory data, is seen in the products of human art, in etching, engraving, wood-carving, or violin playing. Nor is it only seen in the play of the more refined finger-muscles; it is seen also in what we are apt to regard as the coarser and grosser muscles of the trunk. The cricketer, the bicyclist, the gymnast; the angler, the archer, and the marksman at the rifle-butts; all these illustrate the pitch of accuracy which the co-ordination of many and differently situated muscles may reach. Let us take the rifleman for further illustration. At a range of 1000 yards, a deviation of the muzzle of the rifle by less than 1/100 of an inch involves a deflection of the bullet when it hits the target of six inches from the centre of the bull. The rifleman, we will Suppose, is lying down prone, supporting his elbow on the ground, and grasping the rifle, say half-way between the fulcrum, where the stock is held to the shoulder, and the free muzzle of the piece. A deviation of the muzzle by 1/100 of an inch to left or right involves,

(165) therefore, a deviation of the hand by half this amount or 1/200 of an inch. But the hand moves around the axis of the arm, and is carried at-the end of a lever consisting of the fore-arm from elbow to wrist, and this movement is effected, in the main, by muscles around the shoulder. A relatively small movement of the point of insertion of one of these muscles produces a relatively large movement of the hand and wrist. Hence there is certainly no exaggeration -- nay rather, we are probably far within the mark -- in saying that the skilful marksman has his motor co-ordination under control to within the 500th if not the 1000th part of an inch; and this in the play of muscles which would not generally be regarded as susceptible of the highest delicacy of such co-ordination. Nor is the accuracy of co-ordination more remarkable than the rapidity with which in some cases it is effected. Instance the violinist playing a rapid passage at sight, the swordsman whose life depends on accurate and rapid parry, or the cricketer at the wicket who has made all the. co-ordi nations necessary for cutting the ball in the second or so that elapses between its delivery and its reaching the crease. Or instance, in the animal world, the dog catching the flying ball, or the swift sweeping down on minute insects.

Such cases as those of the swordsman and the cricketer serve to bring out another feature in perfected skill, namely, the suggestive value, through the organization of experience, of the initial stages of the action, the effects of which are to be met by the skill, and the part performance of the answering action in advance. Shortly after the ball has left the hand of the bowler, the batsman is prepared to strike in a certain way. Of course, lie is still oil tile alert for the ball may shoot, and this will necessitate a rapid and special co-ordination. So, too, the swordsman knows from the first movement of his adversary's point what is likely to follow, and the antagonist he fears most is the master of newly

(166) devised methods. And so, too, when we watch two dogs fighting, or two well-matched cocks in a farm-yard, we see how every movement and every initial stage of attack are closely watched and call forth the answering movements, which are in turn not less closely watched by the antagonist.

Now I suppose we may take it for granted that the per- fecting of skill under conscious guidance cannot be effected unless the net results of motor co-ordination come within the ken of consciousness. But, seeing how delicate is the co-ordination of motor impulses, which must often, be very numerous, it is at first sight somewhat remarkable that it is seemingly only of the net results, scarcely at all, if at all, of the details, that consciousness., is aware. Take, for example, the case of the rifleman, which we briefly considered. I doubt whether many marksmen could tell us, in the absence of experiment and observation specially directed to this end, whether the muscular adjustments, the net results of which he is consciously or subconsciously utilizing, occur mainly in the wrist, in the forearm, in the upper arm, or in the shoulder. Perhaps the last muscles be would think of particularizing are those around the shoulder-blade. But if he were wise enough to state only what he actually experiences, he would probably say, " I am only aware generally of certain effects upon the direction of the rifle ; I am unaware of any of the details of the process." But though in practical experience we are unaware of these details, it is just these details which give accuracy to the general adjustmet-it of the net results as a whole. And psychology must attempt to explain this seeming paradox.

Let us first notice what a boon it is to consciousness that it has not to deal with all the details. How many muscles are concerned in maintaining a man in the erect position when he is standing at ease I do not profess to know. But I question whether there is a physiologist living who could give an accurate diagrammatic representation of the relative

(167) intensity of the innervation of, let us say, a hundred of the most important of these muscles. And when a man, instead of quietly standing at ease, walks,. or runs, or cuts a bail at cricket, the duly graduated intensities of the series of innervations involved are quite beyond our powers of descriptive analysis. And yet, what more easy than to walk, or run, or even make a decent cut at cricket? It is a great boon that all the subtle details are left to physiological co-ordination, while consciousness is free to deal only with the net results, or groups of co-ordinations as wholes; that a number of physiological impulses conspire to form a single motor-sensation.

And the method employed by consciousness is the method of trial and error. 'rake the case of the marksman. His object is to find that motor adjustment which shall produce certain effects in his visual field, so that, on a still day, the sights and the centre of the bull are in a Tight line. And when, by trial and the selection of the successful adjustment, he reaches the desired result, he has to exercise control over the motor adjustment so as to prevent its falling away from accuracy. That the net results of the motor adjustments are really felt, and accurately felt, seems to be conclusively shown by such an experiment as the following. Stand before a target with a pistol. Having taken a view of the target, shut the eyes, raise the pistol, and fire, You will perhaps be surprised at the comparative accuracy of your aim. You have, however, fired too high, and to the left. Fire again under similar conditions. You will find that you have corrected, probably over-corrected, your previous error. And this you could not possibly have done unless the not results of the motor adjustments had been represented in consciousness with very considerable accuracy. We are perhaps apt to be misled by the fact that motor adjustments, except for physiological and psychological

(168) purposes, are seldom matters which we attempt to describe or explain to our neighbours. Through language we come to live in such a world of description and explanation,. that we are in danger of fancying that what we do not deal with in these ways does not come into consciousness at all. Now it is one of the characteristic peculiarities of skill, that you cannot effectually describe or explain how the motor adjustments are to be made. Hence it comes that five minutes' demonstration is worth more than five hours' talking where the object is to impart skill. It is of comparatively little use to describe or explain how a skilled feat is to be accomplished- it is far more helpful to show how it is done And when we do describe or explain, we do so, not in terms of the motor adjustments themselves, but of their visible effects. In teaching a boy to play billiards, we mingle some description with our demonstration ; but what we describe is not the motor adjustments, but their effects. We say, "Strike your own ball here, moderately hard, and aim to hit the red on this chalk mark I made on it." He plays, and fails. We explain that the failure was due to his striking his own ball too hard, and the red too centrally and full),, and bid him try again. Gradually, by trial and error, lie acquires the skill we would impart. But his attention has been fixed throughout on the effects of the motor adjustments, not on the motor adjustments themselves. He would find it exceedingly difficult to describe these motor adjustments as such. And he might even fancy, like some worthy people whom I have met, that they do not enter the conscious field at all. Experiment and observation directed to that end would soon, however, convince him, if he cared to look into the matter, that they are not only not unfelt, but that they are felt with an accuracy that is somewhat surprising. They are, however, habitually marginal in consciousness, and only for purposes of psychological analysis are dragged into the focus.


A good example of motor adjustments, which though marginal are certainly not unfelt in their net results, is afforded by the production of the voice in singing. And here no description nor explanation is of much service. We sound or sing a note to a child. At first the attempts to reproduce the same note are perhaps somewhat wild. The voice pitches now here now there, now too high and now too low. But after some attempts, and often some sliding, the note is caught, and is then held to with some steadiness, if tire child have a musical ear. Gradually control is gained over the laryngeal apparatus, until the visual stimuli of a vocal score suggest with accuracy and rapidity a sequence of intervals, each of which involves a special motor adjustment. And these motor adjustments are certainly not unfelt. I do not mean merely that the whole process of learning to sing at sight would be inexplicable if they were unfelt; I mean that I personally feel them with great distinctness. If I am looking over some new songs in a music-shop, I quite clearly feel the motor adjustments necessary for singing the notes set down, though I do not murmur a sound. And if the song runs up beyond my vocal range, I have an uncomfortable strained sensation in the throat. For every note I can sing I have a separate motor-sensation - and this sensation, though for psychology an undecomposable element in consciousness, is physiologically the net result of a great number of impulses from the several parts of the larynx. And the acquisition of skill in singing at sight involves the nice correlation of these motor -sensations, with certain visual sensations due to stimuli from the vocal score, and certain auditory sensations which accompany the production of the voice. Of course this analysis is incomplete. Motorsensations accompanying the breathing, and the position of the tongue, lips, and mouth organs, require delicate correlation with the laryngeal and auditory sensations; -and no doubt there are further subsidiary correlations.


I have said so much concerning skill, because, in the correlations it involves, we have some of the most delicate and finished results of the selective synthesis of senseexperience or consentience. And I have said so much concerning the human aspects of skill because it is necessary, in. accordance with the method of interpretation adopted in this work, to study the psychology of skill at first hand in order that we may infer what takes place in the minds of animals. I think there can be no question that the acquisition of perfected skill by the dog or the elephant, by thee beaver, the swift, or the snake-bird, is effected in analogous ways to those by which it is effected in man, excepting in so far as in man there is a certain amount of guidance by description and explanation. This factor is certainly absent in animals. No one ever tau-lit a dog to perform the simplest trick by describing or explaining how it is done. Animals have to rely first on the internal promptings to satisfy hunger or other emotional affections; secondly, on parental guidance - and thirdly, on the influence of what has been termed tradition -- that is, the continuity of habit in a community. Animals which live in herds, packs, of flocks, are born into a community which perform certain actions in certain ways, and through imitation of these traditional proceedings they have a strong tendency to act in like manner But the acquisition of skill, however prompted, is essentially the individual perfecting under conscious control, of activities, the basis of which is an inherited aptitude. This perfecting involves the correlation of sense-data, visual, auditory, olfactory, and so forth, on the one hand, and motor on the other hand -and it is furthermore inexplicable in the absence of motor- sensations which enter, if only marginally, into the field of conscious experience.

It is through skill, and the application of skill, that animals deal so successfully with their environment. For

(171) when skill has been acquired its application is based on association under the varied and varying conditions of sense-experience. The application is essentially a practical matter in accordance with the needs and requirements of a life that is full of vicissitudes. By the more intelligent animals every favourable association is utilized and becomes a factor in the further development of experience. In future chapters the nature and range of intelligent adaptation to circumstances will come under our notice and will receive fuller illustration. All such intelligent adaptation falls within the range of sense-experience, which deals with sense-data of all kinds, and correlates them for the purposes of practical guidance, thus enabling the animal to carry out its life-activities and to meet the varying exigencies of a complex environment.

In conclusion, it should be remembered that both in the delicacy of their sensory endowment and in the ability to deal with that environment by sense-experience, animals are probably in some respects distinctly in advance of man. Witness the delicacy of the sense of smell in some animals enabling them to do that which no man could do so well. I think it not at all improbable that their powers of rapid ,flight in the free medium of the air have induced in birds a delicacy and high specialization of the sense of direction of the movements of the body as a whole, of which we slow treaders of the ground can scarcely form any conception. And this perhaps is a factor in that most difficult and complex question,-- one that involves a good deal more than instinct only,-- I mean the migration of birds. Very possibly our own endowment, in this sense of direction of movement, is very degenerate - still more probably we civilized folk do not make much use of the sensory endowment that we have, relying rather on our knowledge through spatial perceptions and conceptions than on our native powers of sense-experience. Savages who in their daily life make more use

(172) of these native powers, and explorers who are led by circumstances to cultivate these powers, have a sense of direction that the city clerk has allowed to lie dormant and unused. He does not cultivate the delicate use of his membranous labyrinth, with its semi-circular canals. Animals do cultivate the use of this sense-organ, and, probably elements contributed thereby enter into the organised and correlated field of sense- experience in a way at which we can but dimly guess.


  1. For March 1886, quoted in Nature, vol. xxxiii. p. 520.

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