Behavior of the Lower Organisms

In higher animals and man we distinguish certain different conditions,— "states of feeling," "emotions," "appetites," "desires," and the like. In all cases except the self, these various states are distinguished through the fact that the organism behaves differently in the different conditions, even though the external stimuli may be the same. We find a parallel condition of affairs in the lower organisms. Here, as we have seen, the behavior under given external conditions depends largely on the physiological condition of the individual. Many illustrations of this fact are given in preceding chapters, so that we need not dwell upon it here.

In the lower organisms we can even distinguish a number of states that are parallel, so far as observation can show, with those distinguished and named in higher animals and man. To begin with some of the simpler ones, the objective correlate of hunger can be distinguished at least as low in the scale as Hydra and the sea anemone. These animals, as we have seen, take food only when hungry, and if very hungry, will take substances as food which they otherwise reject. Doubtless hunger could be detected in still lower organisms by proper experiments. A resting condition comparable to sleep is found, as we have seen, in the flatworm (p. 253), while there seems to be no indication of such a state in the infusoria (p. 181). Fatigue can of course be distinguished in all living things, including separated muscles.

Correlative with hunger, there exists a state which corresponds so far as objective evidence goes with what we should call in higher animals a desire for food. Hydra when hungry opens its mouth widely when immersed in a nutritive liquid. In the flatworm, we can distinguish a certain physiological condition in which the animal moves about in an eager, searching way, as if hunting for food. Even in Amoeba we find a pertinacity in the pursuit of food (p. 14 and Fig. 21) such as we would attribute in a higher animal to a desire for it.

All the way up the scale, from Amoeba and bacteria to man, we find that organisms react negatively to powerful and injurious agents. In man and higher animals such reactions are usually said to be due to pain. In the lower organisms the objective facts are parallel, and naturally lead to the assumption of a physiological state similar to what we have in the higher forms. As to subjective accompaniments of such a state we of course know nothing in animals other than ourselves. The essential cause of the states corresponding to pain is "interference with any of the processes of which the organism is the seat, and the correlate in action of these states is a change in movement. This point will be developed in our final chapter.

A similar basis exists for distinguishing throughout the organic series a physiological state corresponding to that accompanying pleasure in man. This is correlated with a relief from interference with the life processes, or with the uninterrupted progression of these processes. In man and higher animals we often find a negative reaction to that which is not in itself injurious, but which is usually followed by something injurious. The sight of a wild beast is not injurious, considered by itself, but as preceding actual and injurious contact with this beast, it leads to powerful negative reactions. Such reactions are said to be due to jear. In fear there is then a negative reaction to a representative stimulus — one that stands for a really injurious stimulation. In lower organisms we find the objective indications of a parallel state of affairs. The infusoria react negatively to solutions of chemicals that are not, so far as we can determine, injurious, though they would naturally, under ordinary circumstances, be immediately followed by a solution so strong as to be injurious. Euglena reacts negatively when darkness affects only its colorless anterior end, though we have reason to believe that it is only the green part of the body which requires the light for the proper discharge of its functions. A much clearer case is seen in the sea urchin, which reacts by defensive movements when a shadow falls upon it, though shade is favorable to its normal functions. Objectively, fear has at its basis the fact that a negative reaction may be produced by a stimulus which is not in itself injurious, provided it leads to an injurious stimulation ; this basis we find throughout organisms.

Sometimes higher animals and man are thrown into a "state of fear," such that they react negatively to all sorts of stimuli, that under ordinary circumstances would not cause such a reaction. A similar condition of affairs we have seen in Stentor and the flatworm. After repeated stimulation, they react negatively to all stimuli to which they react at all. The general fact of which the reactions through fear are only a special example is the following: Organisms react appropriately to representative stimuli. That is, they react, not merely to stimuli that are in themselves beneficial or injurious, but to stimuli which lead to beneficial or injurious conditions. This is as true of positive as of negative reactions. It is true of Amoeba when it moves toward a solid body that will give it an opportunity to creep about and obtain food. It is true of Paramecium when it settles against solids (even bits of filter paper), because usually such solids furnish a supply of bacteria. It is true of the colorless flagellate Chytridium and the white Hydra, when they move toward a source of light and thus come into the region where their prey congregate. There seems to be no general name for this positive reaction to a representative stimulus. In man we call various subjective aspects of it by different names, — foresight, anticipation, prudence, hope, etc.

The fact that lower as well as higher organisms thus react to representative stimuli is of the greatest significance. It provides the chief condition for the advance of behavior to higher planes. At the basis of reaction of this character lies the simple fact that a change, even though neutral in its effect, may cause reaction (p. 294). This taken in connection with the law of the resolution of physiological states (p. 291) permits the establishment of a negative or positive reaction, as the case may require, as a response to a given change. The way in which this may take place we have attempted to set forth on page 316.

Related to these reactions to representative stimuli are certain other characteristics distinguished in the behavior of man and higher animals. The objective side of memory and what is called habit is shown when the behavior of an organism is modified in accordance with past stimuli received or past reactions given. If the behavior is merely changed in a way that is not regulatory, as by fatigue, we do not call this memory. In memory the reaction is modified in such a way that it is now more adequate to the conditions to be met. Habit and memory in this objective sense are clearly seen in the Crustacea, and in the low accelous flatworm Convoluta (p. 255). Something of a similar character is seen even in the protozoan Stentor. After reacting to a weak stimulus which does not lead to an injurious one it ceases to react when this stimulus is repeated, while if the weak stimulus does lead to an injurious one, the animal changes its behavior so as to react next time in a more effective way; and it repeats this more effective reaction at the next incidence of the stimulus. Habit and memory, objectively considered, are based on the law of the resolution of physiological states (p. 291), which may be set forth in application to the present subject as follows: If a given physiological state, induced by a stimulus, is repeatedly

resolved into a succeeding state, this resolution becomes easier, and may take place spontaneously, so that the reaction induced is that due primarily to the second physiological state reached. Wherever we find this law in operation, we have the ultimate basis from which habit and memory (objectively considered) are developed. From memory in the general sense it is customary to distinguish associative memory. This is characterized objectively by the fact that the response at first given to one stimulus comes, after a time, to be transferred to another one. Examples of associative memory are seen in the experiments of Yerkes and Spaulding on crustaceans, described in Chapter XII. It may be pointed out that the essential basis for associative memory is the same law of the resolution of physiological states which we have set forth in the last paragraph as underlying ordinary memory. The physiological condition induced by the first stimulus (sight of the screen, in Spaulding's experiments) is regularly resolved into that due to the second stimulus (food, in the experiments just mentioned). After a time the resolution becomes spontaneous, so that the physiological state primarily due to the food is reached immediately after the introduction of the screen, even though no food is given. There seems to be no difference in kind, therefore, between associative memory and other sorts ; they are based on the same fundamental law. The existence of associative memory has often been considered a criterion of the existence of consciousness, but it is clear that the process underlying it is as readily conceivable in terms of matter and energy as are other physiological processes. Even in inorganic colloids, as we have seen (p. 317), the properties depend on the past history of the colloid, and the way in which it has reached the condition in which it is now found. If this is conceivable in terms of matter and energy, it is difficult to see why the law of the readier resolution of physiological states is not equally so.

Intelligence is commonly held to consist essentially in the modification of behavior in accordance with experience. If an organism reacts in a certain way under certain conditions, and continues this reaction no matter how disastrous the effects, we say that its behavior is unintelligent. If on the other hand it modifies its behavior in such a way as to make it more adequate, we consider the behavior as in so far intelligent. It is the "correlation of experiences and actions" that constitutes, as Hobhouse (1901) has put it, "the precise work of intelligence."

It appears clear that we find the beginnings of such adaptive changes of behavior even in the Protozoa. They are brought about through the law in accordance with which the resolution of one physiological state into another takes place more readily after repetition, — in connection with the other principle that interference with the life processes causes a change of behavior. These laws apparently form the fundamental basis of intelligent action. This fundamental basis then clearly exists even in the Protozoa ; it is apparently coextensive with life. It is difficult if not impossible to draw a line separating the regulatory behavior of lower organisms from the so-called intelligent behavior of higher ones ; the one grades insensibly into the other. From the lowest organisms up to man behavior is essentially regulatory in character, and what we call intelligence in higher animals is a direct outgrowth of the same laws that give behavior its regulatory character in the Protozoa.

Thus it seems possible to trace back to the lowest organisms some of the phenomena which we know, from objective evidence, to exist in the behavior of man and the higher animals, and which have received special names. It would doubtless be possible to extend this to many other phenomena. Many conditions which we can clearly distinguish in man must be followed back to a single common condition in the lower organism. But this is what we should expect. Differentiation takes place as we pass upward in the scale in these matters as in others. Because we can trace these phenomena back to conditions found in unicellular forms, it does not follow that the behavior of these organisms has as many factors and is as complex as that of higher animals. The facts are precisely parallel with what we find to be true for other functions. Amoeba shows respiration, and all the essential features of respiration in man can be traced back to the condition in such an organism. Yet in man respiration is an enormously complex operation, while in Amoeba it is of the simplest character possible — apparently little more than a mere interdiffusion of gases. In the case of behavior there is the same possibility of tracing all essential features back to the lower organisms, with the same great simplification as we go back.

All that we have said thus far in the present chapter is independent of the question whether there exist in the lower organisms such subjective accompaniments of behavior as we find in ourselves, and which we call consciousness. We have asked merely whether there exist in the lower organisms objective phenomena of a character similar to what we find in the behavior of man. To this question we have been compelled to give an affirmative answer. So far as objective evidence goes, there is no difference in kind, but a complete continuity between the behavior of lower and of higher organisms.

Has this any bearing on the question of the existence of consciousness in lower animals? It is clear that objective evidence cannot give a demonstration either of the existence or of the non-existence of consciousness, for consciousness is precisely that which cannot be perceived objectively. No statement concerning consciousness in animals is open to verification or refutation by observation and experiment. There are no processes in the behavior of organisms that are not as readily conceivable without supposing them to be accompanied by consciousness as with it.

But the question is sometimes proposed : Is the behavior of lower organisms of the character which we should "naturally" expect and appreciate if they did have conscious states, of undifferentiated character, and acted under similar conscious states in a parallel way to man ? Or is their behavior of such a character that it does not suggest to the observer the existence of consciousness? If one thinks these questions through for such an organism as Paramecium, with all its limitations of sensitiveness and movement, it appears to the writer that an affirmative answer must be given to the first of the above questions, and a negative one to the second. Suppose that this animal were conscious to such an extent as its limitations seem to permit. Suppose that it could feel a certain degree of pain when injured; that it received certain sensations from alkali, others from acids, others from solid bodies, etc., — would it not be natural for it to act as it does? That is, can we not, through our consciousness, appreciate its drawing away from things that hurt it, its trial of the environment when the conditions are bad, its attempting to move forward in various directions, till it finds one where the conditions are not bad, and the like? To the writer it seems that we can; that Paramecium in this behavior makes such an impression that one involuntarily recognizes it as a little subject acting in ways analogous to our own. Still stronger, perhaps, is this impression when observing an Amoeba obtaining food as shown in Figs. 19 and 21. The writer is thoroughly convinced, after long study of the behavior of this organism, that if Amoeba were a large animal, so as to come within the everyday experience of human beings, its behavior would at once call forth the attribution to it of states of pleasure and pain, of hunger, desire, and the like, on precisely the same basis as we attribute these things to the dog. This natural recognition is exactly what Munsterberg (1900) has emphasized as the test of a subject. In conducting objective investigations we train ourselves to suppress this impression, but thorough investigation tends to restore it stronger than at first.

Of a character somewhat similar to that last mentioned is another test that has been proposed as a basis for deciding as to the consciousness of animals. This is the satisfactoriness or usefulness of the concept of consciousness in the given case. We do not usually attribute consciousness to a stone, because this would not assist us in understanding or controlling the behavior of the stone. Practically indeed it would lead us much astray in dealing with such an object. On the other hand, we usually do attribute consciousness to the dog, because this is useful ; it enables us practically to appreciate, foresee, and control its actions much more readily than we could otherwise do so. If Amoeba were so large as to come within our everyday ken, I believe it beyond question that we should find similar attribution to it of certain states of consciousness a practical assistance in foreseeing and controlling its behavior. Amoeba is a beast of prey, and gives the impression of being controlled by the same elemental impulses as higher beasts of prey. If it were as large as a whale, it is quite conceivable that occasions might arise when the attribution to it of the elemental states of consciousness might save the unsophisticated human being from the destruction that would result from the lack of such attribution. In such a case, then, the attribution of consciousness would be satisfactory and useful. In a small way this is still true for the investigator who wishes to appreciate and predict the behavior of Amoeba under his microscope.

But such impressions and suggestions of course do not demonstrate the existence of consciousness in lower organisms. Anv belief on this matter can be held without conflict with the objective facts. All that experiment and observation can do is to show us whether the behavior of lower organisms is objectively similar to the behavior that in man is accompanied by consciousness. If this question is answered in the affirmative, as the facts seem to require, and if we further hold, as is commonly held, that man and the lower organisms are subdivisions of the same substance, then it may perhaps be said that objective investigation is as favorable to the view of the general distribution of consciousness throughout animals as it could well be. But the problem as to the actual existence of consciousness outside of the self is an indeterminate one; no increase of objective knowledge can ever solve it. Opinions on this subject must then be largely dominated by general philosophical considerations, drawm from other fields.

Everywhere in the study of life processes we meet the puzzle of regulation. Organisms do those things that advance their welfare. If the environment changes, the organism changes to meet the new conditions. If the mammal is heated from without, it cools from within ; if it is cooled from without, it heats from within, maintaining the temperature that is to its advantage. The dog which is fed a starchy diet produces digestive juices rich in enzymes that digest starch ; while under a diet of meat it produces juices rich in proteid-digesting substances. When a poison is injected into a mouse, the mouse produces substances which neutralize this poison. If a part of the organism is injured, a rearrangement of material follows till the injury is repaired. If a part is removed, it is restored, or the wound is at least closed up and healed, so that the life processes may continue without disturbance. Regulation constitutes perhaps the greatest problem of life. How can the organism thus provide for its own needs? To put the question in the popular form, How does it know what to do when a difficulty arises? It seems to work toward a definite purpose. In other words, the final result of its action seems to be present in some way at the beginning, determining what the action shall be. In this the action of living tilings appears to contrast with that of things inorganic. It is regulation of this character that has given rise to theories of vitalism. The principles controlling the life processes are held by these theories to be of a character essentially different from anything found in the inorganic world. This view has found recent expression in the works of Driesch (1901, 1903).

Nowhere is regulation more striking than in behavior. Indeed, the processes in this field have long served as the prototype for regulatory action. The organism moves and reacts in ways that are advantageous to it. If it gets into hot water, it takes measures to get out again, and the same is true if it gets into excessively cold water. If it enters an injurious chemical solution, it at once changes its behavior and escapes. If it lacks material for its metabolic processes, it sets in operation movements which secure such material. If it lacks oxygen for respiration, it moves to a region where oxygen is found. If it is injured, it flees to safer regions. In innumerable details it does those things that are good for it. It is plain that behavior depends largely on the needs of the organism, and is of such a nature as to satisfy these needs. In other words, it is regulatory.

Behavior is merely a collective name for the most obvious and most easily studied of the processes of the organism, and it is clear that these processes are closely connected with, and are indeed outgrowths from, the more recondite internal processes. There is no reason for supposing them to follow laws different from those of the other life processes, or for holding that regulation in behavior is of a different character from that found elsewhere. But nowhere else is it possible to perceive so clearly how regulation occurs. In the behavior of the lowest organisms we can see not only what the animal does, but precisely how this happens to be regulatory. The method of regulation lies open before us. This method is of such a character as to suggest the possibility of its general applicability to life processes. In the present chapter we shall attempt to sum up the essential points in regulation as shown in behavior, and to make some suggestions as to its possible application to other fields.

In the lower organisms, where we can see just how regulation occurs, the process is as follows: Anything injurious to the organism causes changes in its behavior. These changes subject the organism to new conditions. As long as the injurious condition continues, the changes of behavior continue. The first change of behavior may not be regulatory, nor the second, nor the third, nor the tenth. But if the changes continue, subjecting the organism successively to all possible different conditions, a condition will finally be reached that relieves the organism from the injurious action, provided such a condition exists. Thereupon the changes in behavior cease, and the organism remains in the favorable condition. The movements of the organism when stimulated are such as to subject it to various conditions, one of which is selected.

This method of regulation is found in its purest form in unicellular organisms. But, as we have seen in preceding pages, it occurs also in higher organisms, and indeed is found in a less primitive form throughout the animal series, up to and including man. It is commonly spoken of as behavior by "trial and error." In connection with this method of behavior, three questions arise, which are fundamental for the theory of regulation. The first is as follows : How is it determined what shall cause the changes in behavior resulting in new conditions? Why does the organism change its behavior under certain conditions, not under others? Second, how does it happen that such movements are produced as result in more favorable conditions ? Third, how is the more favorable condition selected? What it this selection and what does it imply ?

Our first and third questions may indeed be condensed into one, which involves the essence of regulation. Why does the organism choose certain conditions and reject others? This selection of the favorable conditions and rejection of the unfavorable ones presented by the movements is perhaps the fundamental point in regulation. It is often maintained that this selection is precisely personal or conscious choice, and that the behavior cannot be explained without this factor. Personal choice it evidently is, and in man it is often conscious choice ; whether it is conscious in other animals we do not know. But in any case this does not remove it from the necessity for analysis. Whether conscious or unconscious, choice must be determined in some way, and it is the province of science to inquire as to how this determination occurs. To say that rejection is due to pain, acceptance to pleasure or to other conscious states, does not help us, for we are then forced to inquire why pain occurs under certain circumstances, pleasure under others. Surely this is not a mere haphazard matter. There must be some difference in the conditions to induce these differences in the conscious states (if they exist), and at the same time to determine the differences in behavior. We are therefore thrown back upon the objective processes occurring. Why are certain conditions accepted, others rejected ?

Let us examine one or two of the simplest cases of such regulatory selection. The green infusorian Paramecium bursaria requires oxygen for its metabolic processes. While swimming about it comes to a region where oxygen is lacking. Thereupon it changes its behavior, turns away, and goes in some other direction. The white Paramecium caudatum does the same, and so also do many bacteria; they likewise require oxygen for their metabolic processes. All reject a region without oxygen. The green Paramecium bursaria comes to a dark region. The water contains plenty of oxygen, hence the metabolic processes are proceeding uninterruptedly, and passing into darkness does not interfere with them. The animal does not change its behavior, but enters the dark region without hesitation. Later the oxygen in the water has become nearly

exhausted. The animal is again swimming about in the light, and the green chlorophyll bodies winch it contains are producing a little oxygen which the infusorian uses in its metabolic processes. Now it comes again to a dark region. In the darkness the production of oxygen by the green bodies ceases; they no longer supply the metabolic processes with this necessary factor. Now we find that the infusorian rejects, the darkness and turns in another direction. The white Paramecium caudatum does not do this, nor do the colorless bacteria. Possessing no chlorophyll, they receive no more oxygen in the light than in the darkness, and they pass into darkness as readily as into light. But many colored bacteria do reject the darkness. They require light in certain other metabolic processes, — in their assimilation of inorganic compounds, — and when they come to the boundary between light and darkness, they return into the light. Most bacteria reject regions containing no oxygen, as we have seen. But in certain bacteria, oxygen is not required for the metabolic processes; on the contrary, it impedes them. These bacteria reject regions containing oxygen, swimming back into the light. In some cases among unicellular organisms the relation of behavior to the metabolic processes is exceedingly precise. Thus, Engelmann (1882 a) proved that in Bacterium (or Chromatium) photonic! ricum the ultra-red and the yellow-orange rays are those most favorable to the metabolic processes (assimilation of carbon dioxide, etc.). When a microspectrum is thrown on these bacteria, they are found to react in such a way as to collect in precisely the ultra-red and the yelloworange. The reaction consists in a change of behavior, — a reversal of movement, — at the moment of passing from the ultra-red or the yellow-orange to any other part of the spectrum.

At that same instant the metabolic processes of course suffer interference. Bacteria are not in nature subjected to pure spectral colors in bands, so that there has been no opportunity for the production of this correspondence between behavior and favorable conditions, through the natural selection of varying individuals. In all these cases the behavior depends upon the metabolic processes, and is of such a character as to favor them. Throughout the present volume we have found similar relations to hold for all sorts of organisms. We find even that when the metabolic processes of a given individual change, the behavior changes in a corresponding way.

Why does the bacterium or infusorian change its behavior and shrink back from the darkness or the region containing no oxgyen ? As a matter of fact, it needs the light or the oxygen in its metabolic processes, and it does not shrink back from their absence unless it does need them. But we have no reason to attribute to the bacterium anything like a knowledge or idea of that relation. We do not need any purpose or idea in the mind of the organism, or any "psychoid" or entelechy, to account for the change of behavior, for an adequate objective cause exists. We know experimentally that the darkness or the lack of oxygen interferes with the metabolic processes. This very interference is then evidently the cause of the change of behavior. The organism is known to be the seat of varied processes, proceeding with a certain energy. When there is interference with these processes, the energy overflows into other channels, resulting in changes in behavior. This statement is a formulation of the facts determined by observation and experiment in the most diverse organisms. It is illustrated on almost every page of the present work.

In the lower organisms the processes of metabolism are the chief ones occurring, and behavior is largely determined with reference to them. In higher organisms these usually retain their commanding role, but an immense number of coordinated and subsidiary processes also occur, and changes in behavior may be induced by interference with any of these. The answer to our first question is then as follows : The organism changes its behavior as a result of interference or disturbance in its physiological processes.

Our second question was : How does it happen that such movements are produced as bring about more favorable conditions ? This question we have already answered, so far as lower organisms are concerned, in our general statement on page 339. The organism does not go straight for a final end. It merely acts, — in all sorts of ways possible to it, — ■ resulting in repeated changes of the environmental conditions. The fundamental fact must be remembered that the life processes depend upon internal and external conditions, and are favored by conditions that are rather generally distributed throughout the environment of organisms. If there were no favorable conditions attainable, of course no change of behavior could attain them. But the favorable conditions actually exist, and if the changes of behavior continue, subjecting the organism to all possible different conditions, a condition will finally be reached that is favorable to the life processes. Often only a slight change of behavior is required in order to bring about favorable conditions. If an organism swims suddenly into a heated area, almost any change in the direction of movement is likely to restore the conditions previously existing. Adjustment, then, is reached by repeated changes of movement.

Our third question was: How does the organism select the more favorable condition thus reached? This question now answers itself. It was the interference with the physiological processes that caused the changes in behavior. As soon therefore as this interference ceases, there is no further cause for change. The organism selects and retains the favorable condition reached, merely by ceasing to change its behavior when interference ceases. Thus in the lowest organisms we find regulation occurring on the basis of the three following facts : —