one to appear on the second trial and on all succeeding trials. But the organism is never constructed in this way. The principles of repetition and recency must operate many times before the threshold of lo becomes lower than that of any other set of arcs. In general it must be ad- mitted that recency is a much less potent factor in habit formation than is frequency. In certain habits such, for example, as those involved in the maze, its influence cannot very well be made out.
Sensory habits. — The problem in sensory habit is much more complicated. We will take (e) of our illus- tration (p. 261). The animal must learn to respond posi- tively always to one of the two stimuli, say yellow, or what amounts to the same thing, negatively to the l)lue. Whether in any given situation the animal actually does both we cannot say until careful tests have been made. The observed result is the same — the animal, in the illus- 270 FIXATION OF ARCS IN HABIT.
tration chosen, always reacts to the yellow regardless of its right or left position (we are assuming that the wave- length difference is always effective from the standpoint of reaction, regardless of the energy difference of the two stimuli, i.e., that the two objects really offer different stimulating values). In order to understand what happens we ask leave to simplify the problem slightly. Instead of two lights, yellow and hliie, we will substitute two problem boxes, respectively A and B, in their places, leaving the other conditions the same, i.e., the two boxes are separated by a partition, the animal is released from the home box as before, etc. In order to further simplify the problem we will use at first only one box, A, in place of the yellow (positively reacted to). We will keep the box on the right side for the first set of trials. Releasing the animal now as before we find exactly the same situation that we found above, i.e., random movements giving place to the definite act of opening the box. After a time the animal, immediately upon release, goes to the right-hand side and opens the box. The next step is to place the box on the left-hand side. The animal, on release, will probably run to the right-hand side, then here and there, finally locating the box and opening it. We then change its position back to the right and repeat the routine. After a time this movement likewise becomes definite. What have we done? Two acts have been established, viz., one of opening the box and the other of following the box. In this case the act of opening was established first and that of following later, but it is easy to see that the act of following must be executed before the act of opening can be executed. Henceforth we shall call the act of following the box (1) and the act of opening (2). Now introduce the second box, B, on the left side, leaving A on the right side. It is essential to our hypothesis that B be somewhat different from A (i.e., offer different stimulating value). Were box B not present the animal would rush immediately to A and open it. But putting box B on the left-hand side introduces a different stimulation, the intensity of which is such that it on its own account tends to release both FURTHER APPLICATION OF PRINCIPLES 271 the act of foUoiving (1) and the act of opening (2). Will the animal go to A or B? That depends purely upon the strength or intensity of the new stimulus (naturally we should consider here the momentary set of the animal and other intra-organic processes, etc). Suppose we intro- duce now the electric shock, and further, that the animal actually goes to B instead of to A. Before the subject reaches B the electric shock produces the avoiding reaction with the consequence that the animal turns over to A. The response to A becomes the most recent act. On the next trial we will assume that the same thing happens. We begin immediately to get the effect of repetition. The operation of the two factors, recency and repetition, combined with the process of substitution, which is dis- cussed in the next paragraph, will finally result in the establishment of the habit (provided the stimuli actually possess different stimulating values for the animal). If now w^e will go back and substitute the two lights, yellow and blue, for the boxes, A and B, and for the act of opening box A, that of going around to the food box, etc., we wdll see clearly that this simplified scheme has given us the essential factors in the formation of sensory habits. We see that the sensory habits are much more complicated than the motor, but that they are not fundamentally different. It may be argued that we have no right to develop the problem in this simplified way: that the habit may be formed when both stimuli are present from the beginning. We admit that the habit may be developed under such conditions but we argue that while the reactions called for on the part of the animal are more complex under those conditions, yet in the end the fixation process takes place as a result of the factors we have in- voked. In this connection we call attention to the almost unanimous verdict of experimenters to the effect that when both stimuli are present from the beginning the habit arises with difficulty or not at all. A reference to our work on the rat (p. 222) where yellow and blue of high intensity were introduced simultaneously at the be- ginning of the experiment, will show that the animal never 272 FIXATION OF ARCS IN HABIT formed the habit. It was only by using the positive stimu- lus alone until a perfect habit resulted that we were finally enabled to introduce the negative stimulus and thus to complete the test.
Substitution. — By substitution we mean that a stimulus which originally did not call out a given response comes later to call it out. Two examples illustrate this very clearly. A green light at first does not call out the salivary secretion in large amounts in the Pawlow type of experi- ment (p. ^Q). After food has been presented immediately after the green light (or simultaneously with it; simul- taneity is not necessary) for a number of times, the green light calls out the secretion in large amounts. Or again: the experimenter claps his hands (A) and lays fish (B) upon the top of a cage containing a cat. The cat climbs to the top of the cage (R) and eats the food. We may put the course of events down in serial form: A, B, R. After a time the eat climbs up (R) immediately after the experimenter claps his hands (A): thus A, R; B seems to have become unnecessary. It is to meet this type of problem that has led Jennings to posit the concept of the '' readier resolution of physiological states." While the two types of behavior differ in several particulars, the processes involved are probably in general the same. We have to suppose, e.g., in the case of the cat's reaction to the signal that on the first trial A aroused general reflex activity (S), while B aroused the definite instinctive (or habitual) act of climbing up (R). In such a case we have to assume further (there is apparently no other hypothesis open) that while A could not arouse R until B had aroused it and thus lowered the resistance across the effector division of the arc (Y) nevertheless it at- tempted to discharge into Y as well as into the more segmentally placed X. I.e., A discharged or tended to dis- charge into E hut at that moment the resistance was great and the impulse passed out over X, producing the move- ments (8), e.g., of clawing at the ivires, purring, etc. We offer the following simplified neural diagram. Fig. 53. Granting the connection between the sensory division of the SUBSTITUTION arc AS and the effector division of the arc BR, we need to account for only one thing, viz., how it comes about that the stimulus aroused by A now passes through Y instead of through X, its original channel. If we watch the train- ing of the animal we find that A and B have to be gone through with serially many times before R will follow upon A. Before the substitution is established the response (R) has become extremely easy to set off (note the premature response which often occurs in human reaction experi- 3 V B MffiBs lir.DmuiiR ments). Resistance has been decreased by use until even the (assumed) weak impulse aroused by A is sufficient to call it out (it is not necessary to suppose that the re- sistance across X has changed).
Repetition of movement in absence of original stimulus. — In both human and animal work we get cases where a series of movements is executed in a fixed order in the absence of the stimulus which originally called them forth. The process is again one of substitution, but some- what more complex than the one considered above. One of the most interesting of such cases is the learning and FIXATION OF ARCS IN HABIT later repetition of nonsense syllables. Presentation of a series of nonsense syllables to the eye may be illustrated as foUoAvs (Fig. 54): FOD DOR Cor BOR COH Fod, Dor, etc., visual stimuli; a, b, c, d, arc running from eye to laryngeal muscle Ij e, segmental sensory neurone ending in mus- cle 1.
As is well known, we are dealing here with the rear- rangement of established habit systems. The visual stimulus Fod sets up an impulse which releases activity in the laryngeal muscle 1 (either silent or overt saying of the word) and the rest of the syllables act in the same way. We know further that after this series has been gone through with a few times presentation (by any method whatsoever) of Fod forces the recall of the remaining syllables. We may illustrate the scheme where all extra- organic stimuli except the original stimulus are removed, as follows (Fig. 55): In order to understand this we must go back to our first diagram. We see that when muscle 1 is thrown into activity by the visual stimulus aroused by Fod, a neural impulse is set up in the muscle spindles in 1. This im- pulse passing inward over the segmental (proprio-eeptive) neurone, e, may discharge theoretically into any muscle of the body but by reason of the high development of LEARNING OF NONSENSE MATERIAL 275 laryngeal habits, it comes about that the discharge back into the other muscles of the larynx is the easiest. But into which one? Before activity has ceased in 1, muscle 2 FOD has been forced into activity by the external visual im- pulse. We make the assumption then that ease of dis- charge into muscle 2 is greatest, and that next in order come 3, 4, 5, 6, etc. Prom this time on muscle 2 may be called into activity equally through the kinsesthetic impulse passing over e or through the visual impulse aroused by Dor. Consequently when Fod is presented and the remain- ing syllables are not presented, it is clear that the appro- priate kinsesthetic impulses discharge in order into muscles 3, 4, 5, 6, etc. We are dealing here with systems already so highly organized that a single reading of a series of seven syllables will often make the repetition of this series pos- sible. It is probable that these segmental arcs are ' ' fixed ' ' as a result of such factors as we have already considered.^^ Physiological principles operative. — Unquestionably the principles of reenforcement, inhibition, and summation of stimuli are constantly operative. When the separate ^^ As is well known other ares than e become established, viz., an are running from 1 to 3, from 1 to, 4. etc.; also from muscle 1 to the muscle which functioned previously to the functioning of muscle 1.
276 FIXATION OF ARCS IN HABIT stages of habit have been more carefully analyzed we can more readily see how such factors operate in detail.
Conclusions. — It is to be hoped that even this tentative and unsatisfactory presentation of the most important principles in fixation will lead to a more definite study of the mechanisms involved. The problem is in such a state that only careful experimentation will enable us to go further in its solution. It is a great deal easier to assume that pleasure stamps in the successful movement and that displeasure stamps out the unsuccessful and to let the mat- ter rest than to institute the necessary experimentation. But behavior has reached a critical stage and such explana- tions, however satisfactory in the past, no longer content us.
BIBLIOGRAPHY Angell, J. R., Psychology. New York, Holt, 1908.
Book, W. F., TTie Psychology of Skill. Missoula, Univ. Montana, Care, H. A., " Principles of Selection in Animal Learning," Psych.
Glasee, 0. C, " The Formation of Habits at High Speed," Jour.
Camp. Neu. and Psych., 1910, XX, 165. JUDD, C. H., Psychology. New York, Scribner's, 1907. PiLLSBURY, W. B., The Essentials of Psychology. New York, Macmillan, 1911. Swift, E. J., Mind in the Making. New York, Scribner's, 1908. Thoendike, E. L., Animal Intelligence. New York, Macmillan, 1911.
CHAPTER VIII THE ABRIDGMENT OF THE LEARNING PROCESS Introduction. — ^Lloyd Morgan's classification of imitation. — Localiz- ing and enhancing the stimulus. — Putting the animal through the act. — Presentation of experimental results: Introduction. A. Primates. B. Cats. C. Dogs. D. Raccoons. E. Rodents. F. Birds. — Summary.
Introduction. — So far in the treatment of habits we have discussed mainly those that have been formed without tui- tion, i.e., by the animal through its perseverance method. That there are so-called higher forms of learning has been warmly advocated by many experimenters and investiga- tors. Such forms have been treated under the general head of imitation. Examination of the concept of imitation shows that there is little agreement as to the meaning which the term should connote. It would seem wiser to treat the subject of imitation solely from the standpoint of behavior. Prom this standpoint real or genuine imitation should refer to a relatively instantaneous regrouping of old hadits (1). It is presupposed that all elements (unit habits) are present and that the stimulus (pattern, act to be imitated or copied) leads to a response which, from the observer's standpoint, is like the pattern. On the other hand, all that experiment- ers seem to have meant by imitation is that we can, by adopting certain methods of procedure, abridge the process of learning, or make learning possible in cases where the animal has failed to form the habit by its own unaided efforts (2). When the problem is approached from the standpoint of (2) it must be readily admitted that there are many factors which can both abridge the process of learn- ing and lengthen it. Some of these factors have already been discussed on p. 235. Whether there is real imitation in the sense of (1) in the animal world cannot be affirmed so readily (p. 281).
278 ABRIDGMENT OF LEARNING PROCESS Lloyd Morgan's classification of imitation. — The point of view suggested above has not, in general, been adopted. Examination of the literature shows that experimenters have usually chosen some anthropomorphic type of classi- fication of imitation, such as that outlined by Morgan, and have conducted their experimental tests in such a way as to throw into relief the expected kind of imitation. (1) Mimicry is the lowest type so far as classification goes. It lies, according to this writer, generally below the level of imitation. It is found widespread among insects. On ac- count of the many enemies which prey upon animals it has been supposed by the Darwinians that under the process of natural selection animals have become inconspicuous, i.e., they have come to resemble (visually as a rule) the objects in their environment. This is supposed to afford protection from enemies. Once the race is established it is easy to see how the variants will be killed off on account of their conspicuousness. On the other hand, conspicuous- ness may be allowed under natural selection where that character is combined with inedibility. Now many con- spicuous edible forms are not eliminated because they have come to resemble the conspicuous inedible forms. We have already discussed the improbability of races arising in this way through the action of the Darwinian mechanisms (p. 166). However that may be, the mere fact of resem- blance as outlined above is unquestionably true. (2) In- stinctive imitation. This kind of imitation depends upon inherited mechanisms. As examples we may cite the fol- lowing instinctive group of activities; drinking, peering intb cracks and holes, etc., warning cries taken up by birds and other animals, etc. Care is not always taken in these illustrations to insure against the possibility of response to a common stimulus, i.e., the stimulus which may have set off the response in the first animal may also have acted upon the other members of the group. There seem to be genuine cases, though, where the stimulus acts upon one animal, inducing an instinctive mode of behavior which in turn becomes the common stimulus causing group activity.
In regard to the first of these types, mimicry, it may be CLASSIFICATION OF IMITATION 279 said that there seems to be no valid reason to consider such phenomena under imitation at all. Mimicry, except in cer- tain cases, is not a form of behavior at all, but a morpho- logical or anatomical character.^ The second division, in- stinctive imitation, falls under the general head of instinct since such acts as we have included in this group are seen at once to be congenital and not in any way involv- ing the process of learning. It is better to group such responses under some such title as that of social instincts. Morgan's third division, (3) intelligent imitation, is the type usually referred to in discussions on imitation in gen- eral. It is in this third class (and in its finer subdivisions, such as inferential imitation, etc.) that we find confusion of meaning. It is openly anthropomorphic. Experimenters have reported the finding of imitation of this type through the use of the following devices: (1) by the experimenter show- ing the animal how to do an act; (2) by allowing a trained animal to perform before an untrained animal; (3) by "putting the animal through" the act; (4) finally by ^' encouraging " the animal. Before trying to evaluate the effects of the above devices, it is presupposed that the ani- mal has failed to learn by his own unaided efforts, or at least that he has worked at the problem indefinitely until the situation no longer offers stimulation for activity, or finally that we are reasonably sure of the number of trials that the animal would take to learn the problem by the perseverance method. If we examine these devices and strip from them their anthropomorphic implications we find that all of them except (3) are methods really for localizing and enhancing the intensity of the stimulus [(3) is sepa- rately considered on p. 282].
Localizing and enhancing the stimulus. — In actual practice the stimulus may be localized and enhanced in a variety of ways: by the experimenter doing the act before the animal; by pointing to the apparatus and moving eer- ^ Numerous exceptions to this statement may be found in fish, e.g., the flounder, and possibly in certain reptiles (the chameleon). There is no justification for considering such responses as these under the head of imitation at all since they depend upon reflex and inherited mechanisms.
280 ABRIDGMENT OF LEARNING PROCESS tain parts of the mechanism, etc.; by allowing one animal to learn by the perseverance method and using him as an imitatee. His attack upon the apparatus will serve the same purpose as that of the experimenter.^ When using this method two things should be kept sharply in mind as was indicated above, p. 277: either (1) the experimenter is trying to call forth a new combination of old habits (i.e., imitation according to our definition; or (2) he is trying to get the animal to form the habit de novo. We have never sharply separated these two issues. Usually we might say (1) has always been in the mind of the experimenters. All of us, in such experiments, have plunged in medias res by giving the animal exceedingly complex acts to imitate with- out being sure that all of the elements are present, or w^hether there was flexibility enough in the elements (p. 49) which were present. What can we hope to get from such an unscientific procedure? Behavior seemingly is estab- lishing the point that each simple coordination (not con- genital) is acquired by the perseverance method, hence the pattern, or the act to be copied should be made up of sim- pler acts already acquired. The novelty present in the act as a whole is the method of combination (temporal spacing of the elements). It may be argued that in all the tests on imitation we are sure that the unit acts are all present be- fore we start. Each one of our monkeys knows how to put his hand up a shute, turn a button, lift up a latch, etc. — we have trained him to do this before setting the pattern for imitation. The reply is " Yes, those coordinations are present, but they are not flexible enough." Nearly every human being knows how to move his feet alternately back- ward and forward and to turn while moving them, yet the average man learns a new dance with appreciable difficulty. IMerely watching the movements of some one else in dancing is not usually a sufficient stimulus to set free the appropriate movements. Most of us have to be pushed, pulled, twisted through it before the act follows of itself (i.e., through the ^ Hobhouse holds that in the ease of some animals a mere hint, i.e., a mere motion towards the correct act, is sufficient to make the animal go through the act correctly.
NATURE OF IMITATION ' 281 action of the proprio-ceptive arcs.) On the other hand, the dancing master and many women, through long practice, have trained their feet and legs as well as their hands and arms, and can execute the variations of the dance the mo- ment the pattern is set. If it is agreed that the above analysis of what is involved in the act of imitation is, in large measure, correct, it is obvious that very few experi- ments so far reported upon animals (and very few of those on children), really touch the problem of imitation (i.e., of making new combinations immediately from among old habits) at all. It may be argued with justice that we can never be sure in advance that there are a sufficient number of coordinations at hand, and that practically all we can do is to take the animal as we find him, subject him to the influences of the devices enumerated, and see what happens. Until it becomes possible to take some an- thropoid apes and bring them up practically as children are brought up, with varied training and with wide educa- tion of hands, it is probable that what we shall mainly be doing in such work is the testing of the formation of habits with stimuli enhanced. But the results of this type cannot be differentiated from the hastening, or the reverse, one gets through introducing pain stimulation, drugs, heighten- ing tonicity through more potent stimuli, — as when toasted cheese is used in the case of the rat instead of bread, sex in the case of the rabbit, etc. Under proper manipulation such factors can be made to hasten or retard a given habit, depending upon the fact whether these stimulations are arranged to reenforce the desired response or to inhibit it. To illustrate what is meant: one can take the female rabbit and enclose her in a cage along with food, and close a door which may be opened by the turning of a button. Activity of the sort calculated to produce the first success will be hastened in the male, which is placed on the outside. Now, if the box is arranged as before with food alone on the inside, and the female is left with the male, the latter will respond to the more potent sex stimulus to the neglect of the problem before him. Rats which have lain down in the maze, — given up the problem, — can be made active