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century students of animal behavior again re to note his actions, including language, during
turned to the problem which dominated be the process of subjective experience, compare
haviorists of the early years of the seventeenth these actions with those in other individuals
century, namely, the reduction of reactions to and base his conclusions upon the relation be-
mechanical principles. Prominent among these tween them.
students were Engelmann, Verworn, Loeb and Precisely the same method is open to him in
Jennings.

regard to other organisms, although it is eviThe work of the last three investigators dent that comparison of actions becomes more mentioned is in a general way very well known. and more difficult as the difference between That of Engelmann, however, seems to have the structure of the organisms involved inbeen to a considerable extent overlooked, al

The problem as to the nature and exthough it is among the very best that has ever tent of pain and pleasure (feeling or sensabeen done in behavior. I should like to refer tion) consequently becomes more and more particularly to his investigations on Euglena, difficult as one descends in the organic realm. published in Pflüger's Archiv in 1882, several This problem can, however, not be avoided. years before any of the others mentioned be The behavior of every individual depends to gan work in this line.

a large extent upon his conclusion regarding Engelmann finally concluded, after years of the nature and extent of feelings in the searching observations on the relation between creatures with which he comes in contact. physico-chemical phenomena and the reactions Human society demands a decision of some in various unicellular forms, that while many sort or another regarding the distribution of of the reactions in these forms are purely these phenomena. Witness the work of the mechanical some of them can not be explained anti-vivisection organizations, societies for the without postulating psychic processes. This prevention of cruelty to animals and charitable conclusion may be responsible for the fact institutions everywhere, all built upon and that his work has not received the attention acting upon decisions regarding this matter. that it deserves.

The problem then resolves itself into this. Thus we see that one problem after another Shall we permit human conduct in reference has dominated the work in behavior. Re to such an important matter to rest upon judgduction of reactions to mechanical principles; ments based upon evidence casually gained or distribution of pain and pleasure; the evolu shall we demand that it rest upon judgments tion of reactions and psychic phenomena; and based upon the results obtained in a compreagain the reduction of reactions to mechanical hensive comparative study of the reactions of principles. What has become of these prob- organisms under experimentally controlled conlems? What are the fundamental problems ditions ? in behavior to-day?

Many anti-vivisectionists and members of

other anti-organizations who shed copious DISTRIBUTION OF PLEASURE AND PAIN tears over cats and dogs in our laboratories do It has often been said that it is impossible

not hesitate to sit all day and impale earthto ascertain whether or not animals experience

worms, crabs and minnows on hooks, and they pleasure and pain and that it is consequently

do not object to the practise in certain tropuseless to attempt to ascertain the distribu

ical regions of turning turtles and cutting tion of such phenomena in the animal king

steaks from them for a week or more while dom. In a sense this is true but in this sense

alive. They assume, of course, that earthit is also true in reference to human beings.

worms, crabs, fishes and turtles do not suffer. Subjective states can be ascertained with Are they correct in this assumption or was certainty by the investigator only as they exist Brooks correct when, after a lifetime of inin himself. He can not be certain that your timate association with animate beings of all pain is like his pain. All that he can do is sorts he said: “I try to treat all living things,

ence.

plants as well animals, as if they may have Whatever else the term consciousness some small part of a sensitive life like my may imply it always implies awareness (subown"? Or are those correct who maintain

jective experience). As to the actuality of this that sensations in all organisms below the up phenomenon, we are, I believe, more certain per stratum of human beings are insignifi- than we are about anything else. The origin, cant?

the evolution and the nature of awareness, the This question can not, at present, be defi processes associated with it and its relations initely answered and it may never be def to objective reality constitute, in my opinion, initely answered but a comprehensive com the most fundamental problems that confront parative study of the reactions of organisms the human mind, and all available methods of bearing directly upon it will unquestionably attack should be brought to bear upon them. make it possible to answer it more nearly The introspection method has been extencorrectly than can be done to-day.

sively used in the investigation of some of the The field in this line is open. Practically problems mentioned. This method is, at presnothing of a thorough going nature has been ent, in disrepute and many have abandoned it done in it. Among the best of the works on altogether in favor of the so-called behaviorthe lower organisms is that of Norman pre method. I do not believe that the tendency to sented some twenty years ago. Norman showed entirely abandon introspection is wholesome, that the squirming reactions in earthworms to although it is of but little importance in refviolent stimulation do not constitute con erence to the question before us, the origin clusive evidence of pain, for the simple reason

and evolution of reactions and consciousness, that when a worm is cut in two the posterior awareness or subjective phenomena. In the part squirms violently while the anterior part investigation of these questions two methods with the brain does not. Reactions in other are promising. One might be called the comorganisms led him to conclude that there is no parative behavior method, the other the method satisfactory evidence of pain in any of the of genetics. invertebrates. But even this work, which, as The method of comparative behavior has stated, is among the best, is far from com been and is still being extensively employed. prehensive and the conclusions are

It consists in the comparison under given quently only meagerly supported.

conditions of reactions in various organisms

including man. It is anthropomorphic in its ORIGIN AND EVOLUTION OF REACTIONS AND PSYCHIO tendencies and owing to this it has been PHENOMENA

severely criticized both justly and unjustly. It has become the fashion among certain

This is doubtless due largely, if not entirely, ultra-modern psychologists to solve the prob

to misapprehensions as to the import of the lem of consciousness by contending that it does method. not exist. This contention is no doubt largely

The method of comparative behavior was verbal. The term consciousness is not very

used almost exclusively by Lubbock, Graber, specifically defined. It is used loosely by Romanes, Darwin and others interested primany, and the controversy as to the existence marily in the evolution of psychic phenomena. of consciousness is rooted in this fact. What These investigators tried to ascertain whether is denied by some is, as I understand it, the

or not this or that animal sees, hears, smells, existence of an entity capable of action and tastes and feels. experience independent of matter. Regarding

The results obtained led them, as previously this I have nothing to say.

stated, to conclude that various animals, bePractically every one who is sane, even the sides man, have subjective sensation. And modern psychologist, admits that he is aware; since it was generally assumed that human behe admits phenomena may have a subjec havior at least to some extent, controlled by tive as well as an objective reference or exist- subjective states, it was thought that the be

conse

havior of other animals is also thus controlled. in the investigations of subjective states in This resulted in the anthropomorphic expla- others, and precarious as the conclusions may nations of reactions current at the time. For be they are far more likely to be correct than example, it was maintained that organisms those formulated without such investigations. which are photo-positive go toward the light We must consequently either abandon this because they hate darkness or love light, that profound problem altogether or proceed along the moth flies toward the candle-flame to sat the line indicated. isfy its curiosity, etc. These explanations have Aside from its bearing on consciousness the justly been severely criticized, and yet the method of comparative behavior has an immethod is not necessarily at fault.

portant bearing on the problems concerning If human conduct is dependent upon sub the evolution of reactions themselves and their jective states, and if other animals have such interrelation, their sequence. In its bearing states, is it not altogether probable that their on this problem comparative behavior is simireactions are also dependent upon subjective lar to comparative morphology. As comparastates? If this is true it is possible to explain tive morphology yields results concerning the in a certain sense reactions in animals on the relation between structures in different orbasis of psychic phenomena. It is maintained, ganisms, so comparative behavior yields results however, that this is putting the cart before concerning the relation between reactions. It the horse, that it consists in attempting to ex is not primarily concerned in the relation beplain the unknown in terms of something still tween the environment and the reactions. Its more unknown. With this contention I do not primar interest lies in the relation between agree, for I hold that every individual knows

the reactions themselves as manifested in vahis subjective sensations better than anything rious organisms. else. The question, then, resolves itself pri In regard to the evolution of reactions, the marily into this. Does conduct depend upon comparative method in behavior must, however, subjective sensations? If it does then it is give way to genetics just as the comparative evident that in the study of behavior it is of method in morphology has. In this field we the greatest importance to ascertain the dis have as yet scarcely made a beginning. It is tribution of such sensations. But whether

a virgin field of great promise. I should like conduct is dependent upon subjective phe to refer to Yerkes's work on mice and Mcnomena or not, knowledge regarding the dis Ewen's on Drosophila. tribution of such phenomena is fundamental; I have pointed out a number of important for it seems to be the only knowledge that bears problems which are dependent for their soluupon the problems of the origin and evolution

tion upon the relations between reactions and of consciousness.

ņot primarily, if at all, upon the nature or the We judge as to the presence and nature of mechanics of the reactions. There are many guch phenomena in others almost wholly by other problems which can be greatly illumincomparing their behavior with ours. We

ated by a study of such relations. I shall reknow that conscious states in ourselves are ac

fer to but one of these, modifiability in becompanied by certain reactions and when we

havior including habit formation and learning see these reactions in others we conclude that

in general. their subjective experience is the same as ours, Much of the recent work on the behavior of and by comparing the conclusions thus reached

the higher animals centers about this problem, regarding subjective experience throughout the work of Thorndike, Morgan, Yerkes, Watthe animate kingdom, we formulate conclu son, Carr and others. The results of this sions as to the origin and evolution of these work have been of inestimable value, practical phenomena. I realize full well that conclu as well as theoretical, and yet it is based alsions based upon such evidence are precarious, most entirely upon the relation between rebut this method is the only method available actions. Practically nothing is known regard

ing the mechanics of the reactions involved, tirely, due to different conceptions as to what and owing to their extreme complexity little a reduction to mechanics involves. is likely to be known for years to come.

I Fundamentally all scientific knowledge is should like to emphasize this point, for there

the same.

It concerns the order of pheare those who appear to hold that a study in nomena not the cause of the order. It is behavior which does not deal with the re rooted in experience and founded upon the duction of reactions to physico-chemical prin- conviction that Nature is orderly, that a pheciples has no practical value.

nomenon that occurs under a given set of conThe study of modifiability in behavior ditions will occur again whenever this set of should be much extended, especially in the in conditions obtains. All of the scientific laws vestigation of the lower forms where it has as that have been formulated are merely exyet received but little attention, and closely pressions summarizing the results of experiassociated with this is the problem of regula ence, and their validity depends upon the extion, so clearly set forth by Jennings in the tent of the experience. They are in no sense closing chapters of his book on the behavior of absolute; any and all of them may have to be lower organisms.

modified as more experience is gained. To Comparative behavior then, in spite of its ascertain and to regulate the order of pheanthropomorphic tendencies is valuable in cer nomena in nature is the purpose of science. tain lines of investigation, and I hope that Mechanics deals with the relation between what I have said may counteract the strong events or phenomena and changes in the conopposition that has developed against it. figuration of material systems associated with However, no matter what may be the imme such events. The reduction of behavior to diate object of behaviorists, practically all of mechanical principles consists in ascertaining them desire to see reactions reduced, as far as the relation between reactions in animated possible, to mechanical principles. What has systems and changes in material configurabeen accomplished in regard to this, and what tions within and outside of such systems. In are the prospects in reference to it?

other words, it consists in ascertaining the

sequence in series of changes in material conTHE MECHANICS OF REACTIONS

figurations ending in reactions. For example, One of the foremost physiologists says in suppose we have an alkaline medium containsubstance: Many reactions have already been ing paramecia and add a bit of acid, thus inreduced to physical and chemical or mechan ducing avoiding reactions. The substance or ical principles and all reactions together with material in the alkaline medium has a certain all life-phenomena can be thus reduced. An arrangement or configuration. When the acid other equally prominent physiologist says:

is added this configuration is changed and this “The attempt to analyze living organisms sets up changes in the material configuration into physical and chemical mechanisms is within the paramecia which result in a reprobably the most colossal failure in the whole sponse. That is, we have a series of changes history of science.

in material configuration ending in a reaction, How is it that the results obtained by two and similar series of changes precede all reeminent and practical investigators in the actions. same general field have led them to conclusions Now, when the mechanist says that reso diametrically opposed, the one maintaining actions have been reduced to mechanical printhat many vital phenomena have been and that ciples, he probably means merely that some of all vital phenomena can be reduced to mechan the changes in material configuration in the ics, the other apparently maintaining that no series ending in reactions have been ascervital phenomena have been and that no vital tained. And when the anti-mechanist says phenomena can be thus reduced? The differ that the attempt to reduce reactions to me ence in these conclusions is in part, if not en chanical principles has been a colossal failure,

he probably means merely that in no such series have all of the changes in material configuration been ascertained. If this is true then both views are doubtless corect; for it can not be disputed that some of the changes in material configuration in series ending in reactions have been discovered in numerous instances, and it can not be demonstrated that all such changes have been discovered in any instance.

Take for example, one of the very simplest, if not the simplest of all responses, changes in ameboid movement. It has been maintained that this reaction is due to changes in surface tension. Similar movements can be induced in inanimate systems. If a bit of potassium bichromate is brought near a drop of mercury in ten per cent. nitric acid the mercury will flow toward the bichromate. This is due to a local reduction in surface tension. This and numerous similar experiments, it is maintained, show that movements in Ameba are due to changes in surface tension. It has, however, recently been demonstrated that changes in surface tension can not produce the force required in certain ameboid reactions. Other factors have consequently been postulated to supply this deficiency. Now this is a perfectly legitimate procedure in scientific investigation. All that I wish to emphasize here is the fact that ameboid movement has not yet been completely reduced to mechanics. Even if it were conclusively demonstrated that every movement and every change in movement in Ameba is directly the result of changes in surface tension, it could still be maintained that the series of changes in material configurations associated with these phenomena is not completely known for such a demonstration would have no bearing upon the problem of the regulation of the movements.

Ameba can move in a homogeneous environment. Consequently, if its movements in such an environment are due to changes in surface tension, such changes are the result of internal factors concerning which practically nothing is as yet known. These factors may be purely physical and chemical, but it certainly can not be maintained that it has

been demonstrated that they are. For all that is known to the contrary there may be nonmaterial factors, entelechies and psychoids, involved in this regulation. Do not misunderstand me, I do not maintain that there are such factors involved, I merely hold that it has not been demonstrated that such factors are not involved.

In reference to regulation which constitutes the very essence of vital phenomena, we have indeed as yet traveled but a short way on the road toward reduction to mechanical principles, and it is mainly in this region that the anti-mechanist operates.

If we are correct in our analysis thus far, the essential difference between the mechanist and the antimechanist or vitalist is found in the fact that the former maintains that all reactions are completely determined by material configurations, and that all of the changes in such configurations can be ascertained, while the latter maintains that the reactions are not thus completely determined and that the changes in material configurations ending in reactions can be ascertained only in part. Which of these views is correct will be known, if it is ever known, only after every possible sequence associated with reactions has been ascertained. Thus it is evident that the mechanistic and vitalistic programs are, in so far as they pertain to experiment and observation, precisely the same. The mechanist holds that all reactions can be reduced to mechanical principles. Consequently he proceeds to ascertain by experimental methods every possible sequence of phenomena ending in reactions. The vitalists hold that some reactions or certain phases in some reactions can not be reduced to mechanical principles. He also must proceed to ascertain by experimental method every possible sequence of phenomena ending in reactions. For this is the only way he can be certain as to where mechanism breaks down and non-material factors begin to act.

But mechanists frequently maintain that faith in vitalism tends to inhibit experimentation, and that it inculcates superficiality. They maintain that when the vitalist gets into

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