The Problem
of Comparative Psychology

A great part of our more recent psychology is functional. This characteristic has manifested itself in two phases of psychological theory. In physiological psychology the attempt is made to parallel so-called psychical phenomena with physiological processes. As the statement of the latter is largely functional and the physiological psychologist assumes a complete parallelism of all psychical phenomena with physical correspondents, there is a strong tendency to give a functional statement to psychical life. This may be the case even when the psychologist has no such purpose in mind. Again, from the standpoint of introspection we have advanced to the doctrine that our ideas are all motor in their nature, i.e., that they tend in some way to realize themselves in overt action. The influence of this doctrine is to interpret the idea in terms of conduct. Here come in the theories of the will which abolish the gap between the intellect and volition, which do away with the abstract thought or idea as separate from action, and see in the volitional process but the realization of the ideal involved in thought or idea. Here also belong the theories of the emotion which connect them on the one side with physical attitudes that are the expression of ideas and on the other with physiological processes by which the idea passes into overt action.

This tendency of psychological theory has great import for the other branches of philosophical discipline. I have already attempted to point out some of the possibilities it carries with in for the general theory of thought. [1] In this article I wish to make some allied suggestions with reference to Comparative Psychology.


Professor James refers to the whole nervous system including the hemispheres as an organized set of paths. These paths connect sense-organs, contractile muscles and secretive glands with the nerve centers which are the store-houses of nervous energy. That which traverses these paths can be nothing but an expression of nervous energy. Within the physiological system the expression of this energy can be nothing but the various movements of the body and the inner nutritive circulatory excretory and reproductive processes which make these motions of the body possible and preserve the form and the species. Without discussing then the value and import of psychical phenomena independent of the physical organism, this conception of the nervous system, plus a parallelistic doctrine, carries with it the conception of a complete statement of all so-called psychical phenomena in terms of overt movements either carried out or inhibited within the system. Such movements would all have a place in a general or comparative physiology, and the assumptions of functional psychology imply that we would also be comparing movements, which correspond at least to all our so-called psychical experience, with movements in the lower forms which would represent whatever psychical experience they may have.

A comparative psychology would result in which the corresponding phenomena would always be present. If comparative psychology means the comparison of the psychical phenomena of man with the same in the lower animals no such presence of corresponding elements can be assumed. It may be said that we are already interpreting the overt conduct of the animal forms through our own, and only after this comparison make the legitimate inferences to the psychical states behind these overt acts. But as long as we insist on continually

(3) cashing our checks drawn on the psychical phase of experience by the overt act, we are subject to an unavoidable error. The abstraction we make of the psychical from the physical is applicable probably if not certainly to our type of intelligence alone. There is in all probability such a qualitative difference between the consciousness of man and what may be ascribed to a lower animal that the results we get for comparison are, on the side of the lower animal, hopelessly uncertain.

(insert 3a)

I will refer to two methods which have been suggested, one that [is] represented by the chart at the beginning of Romanes' Mental Evolution in Man." Here we find a series of so-called "products of intellectual development" or in other words psychical phenomena. These begin with nervous adjustments with which consciousness is supposed to appear. Then follow pleasures and pains, memory, primary instincts, association by contiguity, recognition of offspring, secondary instincts, association by similarity, reason, recognition of persons, communication of ideas, recognition of pictures, understanding of words, dreaming, understanding mechanisms, use of tools, indefinite morality. To these psychical states are paralleled in so-called psychological series Coelenterata, Enchinodermata, larvae of Insects, Annelida, Mollusca, Insects and Spiders, Fish and Batracia, Higher Crustacea, Reptiles and Cephalopods, Hymenoptera, Birds, Carnivora, Rodents and Ruminants, Monkeys and Elephants, Arthropoid Apes and dogs.

Here we have a series of faculties that are supposed to appear in the order of the animals given. The mere examination of these faculties or, if one prefers, these stages of psychical experience shows that there is no psychical principle by which these stages succeed each other, and that so far as they can be coordinated it is by criteria of overt action although the content is supposed to be psychical. There is no inner reason for the succession of recognition of offspring and secondary instincts to association by contiguity followed by association by similarity and reason. There are overt expressions of intelligence which are perhaps suggested by these, but an interpretation in psychical terms that imply ideas associated by contiguity in one animal and those associated by similarity in another is hopelessly futile.

Professor Lloyd Morgan attack the problem with more feeling for method. Speaking of the study of other minds that our own as a basis for comparative psychology he says "Its conclusions are reached not by a simply inductive process as in Chemistry or Physics, in Astron-

(insert 3b) omy, Geology, Biology, or other purely objective sciences, but by a doubly inductive process .......... First the psychologist has to reach, through induction, the laws of mind as revealed to him in his own conscious experience ..........This is the one inductive process. The other is more objective. The facts to be observed are external phenomena, physical occurrences in the objective world .......... Both inductions, subjective and objective, are necessary .......An then finally the objective manifestation in conduct and activity have to be interpreted in terms of subjective experience. The inductions reached by the one method have to be explained in the light of inductions reached by the other method.

The meaning of this is that we cannot estimate the intelligence of lower forms without constantly present each act of another individual in terms of our own psychical consciousness. Not only must we recognize the overt actions as purposive and adapted to proclude a certain stimuli but we must also be ready to present a counterparts of these the states of inner consciousness of the individual before we can compare this individual wit ourselves or another. If our scientific method requires this unremitting presentation in terms of psychical consciousness it is evidently impossible to pursue a comparison of our own intelligence with that of lower forms. We cannot reproduce such states of consciousness from lower animals, and it is a contradiction in terms to call such vague guessing a scientific method

(3 continued)

If there is to be a comparative science at all, there must be comparable terms, and the comparison must confine itself so far as it can hope to be scientific to such terms. If we can express our own intelligence in terms of overt action and these acts can be compared with those of lower forms and we can keep within this field, such a science is possible. Afterwards we can draw what conclusions we may in regard to the point at which consciousness first appears, its content in the different forms, and the curve of its evolution, but these speculations will be outside of the actual comparison with which this discipline deals.

The comparable objects would be the acts of animal forms. The definition of the object however would be taken from our own experience -- not from the so-called psychical content of the act,

(4) but from the organization of our conduct which leads us to select out and hold together certain motions and call them acts. We may find out what an overt act is in our experience. We may find similar acts in the life-processes of other forms and we may compare them. The first task then of the science is the definition of the act.

The attack upon this problem can be made from the vantage ground of our own experience. When one acts overtly he moves toward a recognized distant object and obtains contact with this object. In most of our acts this contact means manipulation of some sort. This exhausts the possibilities of our movements. We have distance senses which put us into relation with objects outside our physical selves; we have organs of locomotion which, acting under the direction of the distance senses, bring us to these objects or carry us away from them towards others. Our contact with the object may represent food or reproductive processes, but even in these cases manipulation precedes, while by far the larger part of our own contact experience is a manipulation of some sort which serves more distant ends. These more distant ends, however, are but repetitions of the same act. [2]


But another demand will be made upon such a conception of the act besides its complete applicability to human experience and to the life of lower forms: it is that we should be able to express by it different degrees of intelligence.  It is a simple matter to show that in a certain sense the physiological processes of all forms of animal life are and must be the same. Ingestion, digestion, assimilation, respiration, with expenditure of the energy gained by these processes in getting more food, maintaining the requisite animal warmth and finally reproducing the form, -- these processes are at bottom identical in all animal and indeed in all but one phase of vegetable life. In higher forms there is an indefinite complication of the process, but it is not possible to grade intelligence simply by the mere complexity of physiological processes taken by themselves. We inevitably take other factors into account, such as adaptability, together with what goes under the term choice. The criterion which is applied unconsciously by all observers of animals has been stated by Romanes in the question, [3] "Does the organism learn to make new adjustments or to modify old ones, in accordance with the results of its own individual experience?" This individual use of experience is accepted by Lloyd Morgan [4] as the criterion of the effective presence of consciousness, or what we consider intelligence akin to our own. This capacity to make use of the past and create afresh, this power to adapt and choose, must be capable of expression in terms of the act if it is to serve

(7) the purpose of interpreting the evolution of intelligence. It is not simply control over the environment that is involved in the expression of intelligence, for this is found in vegetable life, and in a high degree among forms which stand comparatively low in the scale. Parasites represent a complete adaptation to, and for their purposes, control over their environments. What is involved is this individual attack upon the problem of control, that is implied in the use of experience, or choice. The conception is one, of course, that calls for an elaborate psychological analysis, but as long as the content is one which if familiar to every one who compares intelligence in animal forms, this may be omitted here, provided it can be shown that what is essential to it is stated in terms of the act. We must define individual control over experience -- this power of adaptation, connating choice, in a formula of the movement toward a recognized object leading to contact-control.

It is symbolism that renders this possible if we look at the problem from the standpoint of consciousness.  It is a symbolic presentation that puts our experience under our control. It is in the form of thought that is essentially symbolic that we are able to analyze, reconstruct, and thus adapt experience in individual ways. This symbolic thought that makes self-consciousness possible, because it is only in this form that it is at the disposal of the individual as individual.  Experience that is deep-bedded in sub-conscious habits, that is never separated from the objects of action, cannot belong to the individual in the passing moment of his ephemeral existence.  In the world of instinct and unquestioned objective validity the individual has nothing that is his own. He but represents the species. He belongs to experience, not experience to him. The possible abstractness

(8) of consciousness is in direct proportion to the concreteness of the individual. The problem is therefore to express symbolism in the formula.

Now there are many ways in which one phase of an overt act stands for another. The line of vision represents the line of steps by which we approach the object. The pull on one side of us represents that on the other in the balanced maintained by opposing muscles, and looking stands for possible handling, etc., etc. In physiological terms, one aspect of these processes must be represented in the response of the other, and in so far as we conceive of such activities being expressed in consciousness there must be a feeling of correspondence or immediate translation of the value of the one phase into the other. But this does not involve consciousness of the symbolic character of any one value. To put it in somewhat different form, in order that anything may have symbolic value, we must be able to dispense with it for the immediate action. If, for example, the value for the contact senses which the object of vision has, were to be abstracted for symbolic purposes, we could not use this for immediate control of conduct. Different colorings and shadings and seen dimensions at different distances mean the solidity and dimensions which the object will have when we grapple with it. That we may assign conscious symbolic value to this seen content would mean that we no longer instinctively reach for and manipulate the object.  If it is symbolic of something, it no long is that something, but if what we see is not presented as existing in contact terms we cannot possibly act with reference to it. Otherwise there would be no difference between our attitude toward an admirable picture of an object

(9) and the object represented by the picture. That any concent may become symbolic it must resign its value for immediate action.

At no point, then within the act in its simplest terms, could this symbolism be found. For the lowest terms to which we can reduce our world involves the elements of relation to a distance sense, approximation and contact. There can exist for us no world in three-dimensional space without these elements. In other words there could be no object of physical perception without a complete act. But no analysis can carry us beyond an object. If we analyze an object into elements, these elements must be objects or the could not be parts of an objective world.[5] The reality of a physical object -- the lowest term to which the physical world can be reduced -- involves the act. Within this act is its simplest terms, symbolism could not appear. If this statement is to provide for symbolism and the type of intelligence which this makes possible, it must indicate an involution of activity in which some one act or corresponding object stands for another. Within the act itself sight may not symbolize contact, for then sight would not involve reaching or grasping -- in other words the world would become a picture without a canvas or a frame. Of course this act must be stated in some way in terms of the environment. Seeing, walking, devouring are all movements whose value and content is found in what is seen or trodden on or torn in

(10) pieces and devoured. If the act is to stand out by itself it must be in terms of an environment that definitely answers to these processes. But this environment must here serve not as occasion for the expression of immediate impulses, but as possible occasion for an act which does not come to immediate expression.

In this way the immediate situation with the impulses it sets free may through its objects be compared with an environment or objective situation that stands for another act. For example a path representing locomotion toward a distant goal, when interrupted by a chasm may be set over against a board which means bridging the chasm. The chasm means a jump, the board means lifting, placing, walking. Immediate impulse leads up to the spring. Through the board we may compare activities it calls forth with the instinctive but inhibited jump. The problem narrows itself to this: When can the object serve the form not  simply as occasion for immediate action but also as a means of adjusting and adapting different impulses? This it seems to me could not take place until the relation toward the environment meant direct reconstruction, not simply mediation of the present impulse. If the form can make another situation, it can give the occasion for another act, and the elements out of which this can arise become symbols  of this act.

Direct control over environment -- manipulation -- gives the possibility of symbolism. The power of control over the objects which through the various distances senses set free our impulses, is also the power of control over the impulses themselves, and the past experience they embody. With the power to construct that object comes to the individual the power to adapt and use the experience those objects represent. The primitive act, illustrated in sight,

(11) movement toward, and seizure of the distant object, brings with it the possibility of reason, or effective consciousness, or choice, or use of past experience for the immediate individual, when manipulation enables it to construct the object to which it responds. When the animal is able to construct the stimulus that brings his inherited and acquired habits to expression he has control over these impulses and their habitual experiences. The construction of the stimulus brings with it the power of adaptation and change. Introspection reveals that we have no power of immediate conscious change in the contraction of the muscle. It is assumed that our consciousness does not accompany the efferent nerve currents at all. On the contrary our consciousness of an activity appears only when nerve currents return from the contracting muscles. Only indirectly can be control our movements and this indirect control is found in selection of the stimulus which sets the impulse free. This control becomes most perfect when manipulation can itself construct the situation out of which the action arises.

We can illustrate the value of this by the mental image. The working image is one that arises through the conflict between the tendencies to action and the inhibition of these tendencies by the situation itself.  Thus the image of a house we are seeking arises when we are brought up before the wrong edifice. With great clearness the stimulus which is needed to give expression to the inhibited impulse stands out before use. A successful working image of this house and its surroundings is one which passes into the present experience interpreting and filling it out so that it becomes not simply the house we seek but a locality with definite relation to the desired spot. The psychological process by which this image that is merely the result of the inhibition of the impulse becomes the working image is somewhat as

(12) follows: The image may readily merge into the present situation interpreting it as indicated above, or this may be impossible without a reconstruction. For example one may be so turned about as regards the locality that the present surroundings are out of all immediate relation to the place expected and presented as an image. An orientation by the points of the compass and other fixed relations becomes necessary. What is essential for such a reconstruction is that there should be in consciousness a schema to which these localities can be referred. It is in this field that the common element if found out of which adaptation is possible. This of course is the reasoning process, that finds a universal by means of which the conflicting phases of experience may be harmonized. Psychologically we have the two tendencies -- one the movement along this path toward an expected house and the opposing tendencies arising from the presence of the other objects. The strange locality and the image of the house will not merge into each other, to serve as stimulus for immediate conduct. The conflict between the two or more impulses, that of entering the edifice present -- being a part of the whole movement up to the point at which we find that it is not the house expected -- and that of moving from it or by it, using it as a negative landmark of the desired goal, this conflict robs the objects about of their content and value as stimuli for mediating the present impulses. In terms of the act the recognition of the distant object and movement have been present but the contacts which consummate the act are lacking. On the other hand the tendencies to carry out these contact processes are inhibited when they are all ready for expression. The ground for the inhibition is the inappropriateness of the immediate contacts. Within the immediate act which is that of reaching a particular

(13) object, any other object is but a stimulus for the direction of approach toward the object. There is then a conflict between two processes: that of attempted contact or manipulation and that of farther procedure. The object represents two conflicting phases of the act. The conflict defines the two tendencies which is of importance. The object may fall readily into the place of a landmark -- the error be corrected, and the movement toward the real goal be taken up again. In this case what may be called the orientation has been perfected. The definiteness of the contact values in their relation to the ground to be passed over simply organizes more perfectly the field of approach. But in case the object refuses to take its place as landmark, and the individual is at a loss to place it within the field of approach, these inhibited contact processes still seek expression. If the tendencies to contact expression cannot merge into the field of approach to the more distant goal -- and therefore the tendencies to movement toward a distant goal are inhibited, -- there will be the opposite possibility of the merging of the process of approach into those of contact, i.e., regard the objects about not as landmarks but as object of contact. The possibility will depend first of all upon the applicability of contact values to the approach values, and second upon the functional value of such a merging to the form.

There can be no question tat the approach value -- the land mark --  is applicable to the contact value. What we may handle and manipulate can become an object for determination of movement, provided the object has any place in the field of approach. Illustration of this is found in the series of provisional goals into which a long journey is divided. We move toward and object seen in the distance, and this object has the vale for the time

(14) being of the goal. Approach to it, however immediate, robs it of the character and a farther goal take its place. Indeed we may say that no object could be a goal which could not also be an object in the field of approach. There is a universality about the land-mark that can cover practically every object which might also be a goal. But that an object should be a goal, implies that it is of functional importance in contact processes. The prominent values that go with contact in lower forms are ingestive and reproductive processes. These are specialized and not capable of application to mere objects of orientation by sight. It is suggestive of this that for these forms mediate goals are not so largely determined by sight as by smell -- for smelling is the projection of the process of eating and in no small degree of reproductions.  The sense of smell therefore is in a certain sense a means of generalization through which, what is only a part of the field of approach may be here also a goal value.  This is not so important to birds who are able to keep within sight of their ultimate goals to a much greater degree than land animals. It is also evident that the capacity for attachment on the part of an animal depends upon his ability to give mediate objects -- such as a master-goal -- values. A dog without a sense of smell would not only be helpless but heartless.

But the sense of smell is capable of only restricted use, because of its lack of connection with other objects than those more or less referable to the eating and reproductive processes, and because it give little reconstructive power -- power to construct a stimulus appropriate for the interrupted activity. On the other hand the process of manipulation is applicable within a comparatively wide field.  Take a map, for example, as an illustration.

(15) By constructing this symbolic presentation of the field of approach -- that is by presenting through the hand to the eye the relation of the objects about to the image of the stimulus needed for the realization of the act -- it is possible to work backwards from the required object to the present situation, and thus reconstruct the field of approach, so that present objects serve as landmarks for the distant goal. The function which manipulation serves here is that of completing the statement suggested in the image of the distant goal -- enabling us to start from that and thus seek out the appropriate means, which may be finally connected with the actually present environment. such a process as this does not necessarily involve the actual drawing of the map. The tactual images of other objects are associated with the goal image. It is evident that this would not be possible, if the contact values of these other objects existed for the form only as satisfaction of actual wants, such as food or protection. They could then be only capable of presentation as ends, not as means except in the sense indicated above.  But if they are present as objects which we can feel and handle as well as final satisfactions of organic wants, they can be freed from their values as ends and become means. Manipulation involves not simply the handling of the object but its possible contact presentation as mental image, and of course includes not simply those objects which can be lifted and manipulated by the hands but the entire actual and possible feeling over of an object, all of that phase of actual experience which comes through the muscular reaction upon the object, the joint sense, and the more or less inhibited tendencies to carry out these processes. Let me repeat that only when the act of sensing the distant object and approaching it can be provisionally completed by contact reactions of manipulation can the experience attain to

(16) the value of an object, which may be used as a symbol. As soon as this is possible, objects which could not otherwise be freed from the particular act may be associated with an indefinite number of goals and attain therefore the mediate goal value which enables us to indefinitely complicate our activity.

(16a) It is possible to answer the questions suggested above in the affirmative.   All objects that are present in terms of manipulation are first of all goal-objects for the primitive act. In so far therefore as any object in the field of approach may be presented in terms of manipulation it may become a goal object. It is possible therefore to allow the inhibited tendency to contact processes which appears, for example when we have reached a false goal, to extend itself to all the surrounding objects. As we saw in a case of immediate and successful orientation the false gold would at once become another object in the field of approach toward the true but still distant goal.  In this case the goal object falls within the processes of approximation. The other case suggested was that in which the goal object refuses to merge in the file of approach. We have just seen that for a form which as powers of manipulation, it is possible to merge objects in the field of approach in the contact activities even when these are inhibited. Such a possibility would not belong to a form which has no universal powers of manipulation. The second question was in reference to the functional value of this extension of the contact values to the field of approach. We have seen that this value is found in the reconstruction of the stimulus which gives control over the impulses which the stimuli set free. Thus the power of presenting the field of approach in contact terms brings with it that of constructing a map, or orienting ourselves by the use of symbolic contact elements.x

(16 cont)

We may find then in the act provisionally completed by manipulation, and the objects for which these act stand, the possibility of symbolism  and all that goes with it in the estimation of intelligence, and we may apply this without necessarily going back to the act to the assumed consciousness of the form.

I have not attempted to give an exhaustive analysis of the act. What I have attempted to show is that all our overt processes and the images of such processes may be reduced to a series of acts which consists in sensing the distant object, approach to it, and contact use of it; that this is applicable to all animal forms, and finally that the peculiar type of intelligence which we find in ourselves, and which has its basis in a symbolic presentation of our world, can be expressed in terms of this act.  We may then compare ourselves with other forms in terms of the act, and in so far there arises the possibility of a comparative science of intelligence which admits of whatever interpretation is possible in terms of our own psychology.

I shall attempt in a later article to show that our control over the physical environment may be stated in these terms.

The University of Chicago

George H. Mead


  1. Suggestions toward a Theory of the Philosophical Disciplines. The Philosophical Review , Jan. 1900.
  2. I have in this bare statement of the act omitted those processes in which the order seems to be reversed, in which we move and manipulate that we may see or hear or smell -- the processes out of which aesthetic experiences, both appreciative and constructive, arise. These aesthetic experiences are most intricate and subtle. Their organic value to the system is very difficult to discover and define. We recognize in general that they are but functions of the distance senses, the eye and the ear for example; that the selective process by which the eye and ear recognized and in some sense constructs its object, is that which is developed more fully in artistic construction and appreciation; that the value which the object of aesthetic appreciation has for us must come back to our possible movements with reference to it, our organic response to these movements, and the contact experiences it may give rise to. In a word the distance value which the object of art has for us must be interpreted ultimately in terms of the act as we have defined it.   Thus music has in it the sound values which give the spoken word its power of calling out action, together with the rythms (sic) of that action. Listening to music is a further evolution of a capacity to recognize this distant object and move toward it. And the value which the music has for us lies in responses, however they may be inhibited, which these sounds call out in the bodily system -- responses which must follow the lines which the reactions to sounds have already drawn.

    Finally a word should be said with reference to social processes by which one form communicates with another, whether through sounds or gesture or movement. The value of these signs and signals is found in providing an object for a distance sense of the other form, but it has its value for the animal that makes it in terms of possible movements toward and contacts with still more distant objects. In a word the processes to which we have referred are but complications of the act as we have defined it, i.e., movement with reference to an object recognized by a distance sense, leading to contact experience. It is evident that a statement made as simple as this applies not only to our own experience but also to all animal life. There is no form which we may wish to bring into comparison with man to which such a definition of the act would not suffice. There would be more hesitation in applying it to human experience than to the life of the lower animals. (this note begins on page 4 of the typescript, continues through page 5 and ends on page 6)
  3. "Mental Evolution in Animals", p 48.
  4. "Habit and Instinct", p. 264.
  5. I am for the present leaving out of the account the abstractions of scientific though which present relations and uniformities of objects, and am dealing with that more primitive analysis which gives what we term physical reality to what later may be presented as law. This is allowable as we are as yet discussing the most primitive stage of human intelligence, that we may bring it into connection with that of lower forms.

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