MALES FEMALES
SETS 80 82 84 86 88 AV. 73 79 83 85 89 AV. OF 10
A 5 5 4 8 5 5.4 5 6 7 7 6 6.2 B 5 3 6 5 6 5.0 7 5 7 6 7 6.4
1 7 7 6 6 6 6.4 7 6 9 4 6 6.4 2 2 1 0 6 6 3.0 6 5 6 5 5 5.4 3 4 5 5 1 2 3.2 6 5 2 4 1 3.6 4 3 4 7 2 0 3.2 4 3 1 4 3 3.0 5 2 3 3 2 4 2.8 – 3 4 3 1 2.7 6 2 2 – 2 2 2.0 – 0 2 2 0 1.0 7 – 1 – 0 1 0.7 – 1 0 2 1 1.0 8 – – – 1 1 1.0 – 1 1 0 0 0.5 9 – – – 0 1 0.5 0 1 1 0 0 0.5 10 – – – 0 0 0 – 0 0 0 0 0 11 – – – 0 0 0 – 0 0 0 12 – – – 0 0 – 0 0 0
TABLE 43
EFFICIENCY OF TRAINING. WHITE-BLACK TESTS AT THE RATE OF 10 PER DAY
MALES FEMALES
SETS 210 220 230 410 420 AV. 215 225 235 415 425 AV. OF 10
A 6 5 6 6 6 5.8 8 4 4 8 5 5.8 B 6 8 8 5 1 5.6 8 7 6 6 2 5.8
1 6 7 6 2 4 5.0 7 6 5 6 4 5.6 2 4 3 1 2 3 2.6 5 6 4 2 5 4.4 3 3 1 4 3 4 3.0 3 3 4 2 5 4.4 4 5 0 3 3 2 3.2 2 1 3 3 3 2.4 5 3 0 4 1 4 2.4 1 3 3 3 3 2.6 6 2 1 4 0 1 1.6 2 1 1 1 0 1.0 7 1 0 3 1 0 1.0 1 1 2 3 3 2.0 8 0 0 1 0 0 0.2 0 0 2 2 3 2.0 9 0 0 0 1 0 0.2 1 0 0 1 1 0.6 10 0 0 0 0 0 2 1 0 2 1.0 11 0 0 0 0 3 0 1 0 0.8 12 0 0 0 0 0 2 0 0.4 13 0 0 0 0 0
14 0 0 0
15 0 0
TABLE 44
EFFICIENCY OF TRAINING. WHITE-BLACK TESTS AT THE RATE OF 20 PER DAY
MALES FEMALES
SETS 72 74 208 240 402 AV. 217 230 245 403 407 AV. OF 10
A 4 6 7 7 6 6.0 5 4 7 7 6 5.8 B 6 4 6 8 7 6.2 7 3 5 8 5 5.6
1 3 5 7 5 5 5.0 3 6 4 4 6 4.6 2 4 3 7 5 4 4.6 7 3 5 4 6 5.0 3 3 3 3 5 3 3.4 4 3 3 2 5 3.4 4 6 3 1 4 5 3.8 5 0 1 2 3 2.2 5 4 1 0 2 3 2.0 6 0 0 1 2 1.8 6 3 1 0 2 2 1.6 4 1 1 0 6 2.2 7 3 2 0 1 1 1.4 1 0 0 0 1 0.4 8 2 0 1 1 0.6 0 3 3 0 2 1.6 9 2 1 1 1 1.0 1 0 0 3 0.8 10 1 2 1 0 0.8 0 1 1 2 0.8 11 3 1 0 0 0.8 0 0 0 0 0 12 1 2 0 0 0.6 0 0 0 0 0 13 0 0 0 0 0 0 0 0
14 0 0 0
15 0 0 0
The results of the ten-test training as they appear in Table 43 need no special comment, for quite similar data have already been examined in other connections. In the case of this table it is to be remembered that each figure represents the number of errors for a single day as well as for a series of ten successive tests. The results of Table 44, on the other hand, appear as subdivided series, since each daily series was constituted by two series of ten tests, or in all twenty tests.
Finally, in Table 45 I have arranged the results of what may fairly be called the continuous training method. In connection with several of the labyrinth experiments of Chapter XIII continuous training proved very satisfactory. It therefore seemed worth while to ascertain whether the same method would not be more efficient than any other for the establishment of a white-black discrimination habit. That this method was not applied to ten individuals as were the two-five-test, the ten-test, and the twenty-test methods is due to the fact that it proved practically inadvisable to continue the tests long enough to complete the experiment. I have usually designated the method as one hundred or more tests daily. I applied this training method first to individuals Nos. 51 and 60. At the end of one hundred and twenty tests with each of these individuals I was forced to discontinue the experiment for the day because of the approach of darkness. In the table the end of a series for the day is indicated by a heavy line. The following day Nos. 51 and 60 succeeded in acquiring a perfect habit after a few more tests.
TABLE 45
EFFICIENCY OF TRAINING. WHITE-BLACK TESTS AT THE RATE OF 100 OR MORE PER DAY
SETS 51[1] 60 87 Av.
OF 10
A 5 5 6 5.3
B 5 3 7 5.0
1 6 6 5 5.7
2 3 2 5 3.3
3 5 4 7 5.3
4 7 4 5 5.3
5 6 2 3 3.7
6 1 1 3 1.7
7 4 2 3 3.0
8 3 3 0 2.0
9 2 2 3 2.3
10 5 0 2 2.3
11 1 2 2 1.7
12 2 1 1 1.3
13 4 1 2 2.3
14 1 2 1 1.3
15 3 1 5 3.0
16 3 3 2 2.7
17 1 0 1 0.7
18 2 0 1 1.0
19 0 0 2 0.7
20 0 0 0
21 0 1 0.3
22 –
23 –
24 –
[Footnote 1: Age of No. 51, 22 weeks. Age of No. 60, 17 weeks. Age of No. 87, 8 weeks.]
The results of the continuous training method for these two mice were so strikingly different from those yielded by the other methods that I at once suspected the influence of some factor other than that of the number of tests per day. The ages of Nos. 51 and 60 at the time of their tests were twenty-two and seventeen weeks, respectively, whereas all the individuals used in connection with the other efficiency tests were four weeks of age. It seemed possible that the slow habit formation exhibited in the continuous training experiments might be due to the greater age of the mice. I therefore selected a healthy active female which was only eight weeks old, and tried to train her by the continuous training method. With this individual, No. 87, the results were even more discouraging than those previously obtained, for she was still imperfect in her discrimination at the end of two hundred and ten tests. At that point the experiment was interrupted, and it seemed scarcely worth while to continue it further at a later date. The evidence of the extremely low efficiency of the continuous method in comparison with the other methods which we have been considering is so conclusive that further comment seems superfluous.
We are now in a position to compare the results of the several methods of training which have been applied to the dancer, and to attempt to get satisfactory quantitative expressions of the efficiency of each method. I have arranged in Table 46 the general averages yielded by the four methods. Although these general results hide certain important facts which will be exhibited later, they clearly indicate that an increase in the number of tests per day does not necessarily result in an increase in the rapidity of habit formation. Should we attempt, on superficial examination, to interpret the figures of this table, we would doubtless say that in efficiency the two-five-test method stands first, the continuous-test method last, while the ten-test and twenty-test methods occupy intermediate positions.
TABLE 46
EFFICIENCY OF TRAINING
Number of Errors in White-Black Series for Different Methods of Training
SETS OF 10 2 OR 5 TESTS 10 TESTS 20 TESTS 100 OR MORE PER DAY PER DAY PER DAY TESTS PER DAY
A 5.8 5.8 5.9 5.3
B 5.7 5.7 5.9 5.0
1 6.4 5.3 4.8 5.7
2 4.2 3.5 4.8 3.3 3 3.4 3.2 3.4 5.3
4 3.1 2.5 3.0 5.3 5 2.7 2.5 1.9 3.7
6 1.5 1.3 1.9 1.7 7 0.9 1.5 0.9 3.0
8 0.7 0.8 1.1 2.0 9 0.5 0.4 0.9 2.3
10 0 0.5 0.8 2.3 11 0 0.4 0.4 1.7
12 0 0.2 0.3 1.3 13 0 0 2.3
14 0 0 1.3
15 0 0 3.0
16 2.7
17 0.7
18 1.0
19 0.7
20 0
We may now apply to the results of our efficiency-of-training tables the method of measuring efficiency which was mentioned at the end of the preceding chapter as the _index of modifiability (that number of tests after which no errors occur for at least thirty tests)_. By taking the average number of tests for the several individuals in each of the Tables 42, 43, 44, and 45 we obtain the following expressions of efficiency:–
METHOD INDEX OF MODIFIABILITY (EFFICIENCY)
Two-five-test 81.7 +- 2.7
Ten-test 88.0 +- 4.1
Twenty-test 91.0 +- 5.3
Continuous-test 170.0 +- 4.8
Since the difference between the indices for the ten-test and the twenty- test methods lies within the limits of their probable errors (+-4.1 and +-5.3) it is evident that it is not significant. Except for this, I think these indices may be accepted as indications of real differences in the value of the several methods of training.
A somewhat different interpretation of our results is suggested by the grouping of individuals according to sex. In Table 47 appear the general averages for the males and the females which were tested by the several methods. The most striking fact exhibited by this table is that of the high efficiency of the twenty-test method for the females. Apparently they profited much more quickly by this method than by the ten-test method, whereas just the reverse is true of the males. I present the data of this table merely to show that general averages may hide important facts.
TABLE 47
EFFICIENCY OF TRAINING
CONDITION MALES FEMALES INDEX OF MODIFIABILITY INDEX OF MODIFIABILITY 2 or 5 tests per day 85.0 80.0 10 tests per day 72.0 104.0 20 tests per day 94.0 88.0 100 or more tests per day 160.0 180.0
From all considerations that have been mentioned thus far the reader would be justified in concluding that I made a mistake in selecting the ten-test method for my study of the modifiability of the behavior of the dancer. That this conclusion is not correct is due to the time factor in the experiments. If the dancer could acquire a perfect habit as a result of twelve days’ training, no matter whether two, five, ten, or twenty tests were given daily, it would, of course, be economical of time for the experimenter to employ the two-test method. But if, on the contrary, the two-test method required twice as many days’ training as the five-test method, it would be economical for him to use the five-test method despite the fact that he would have to give a larger number of tests than the two- test method would have demanded. In a word, the time which the work requires depends upon the number of series which have to be given, as well as upon the number of tests in each series. As it happens, the ten-test method demands less of the experimenter’s time than do methods with fewer tests per day. The twenty-test method is even more economical of time, but it has a fatal defect. It is at times too tiresome for both mouse and man. These facts indicate that a balance should be struck between number of tests and number of series. The fewer the tests per day, within the limits of two and one hundred, the higher the efficiency of the method of training, as measured in terms of the total number of tests necessary for the establishment of a perfect habit, and the lower its efficiency as measured in terms of the number of series given. The greater the number of tests per day, on the other hand, the higher the efficiency of the method in terms of the number of series, and the lower its efficiency in terms of the total number of tests. By taking into account these facts, together with the fact of fatigue, we are led to the conclusion that ten tests per day is the most satisfactory number.
If my time and attention had not been fully occupied with other problems, I should have determined the efficiency of various methods of training in terms of the duration of habit, as well as in terms of the rapidity of its formation. As these two measures of efficiency might give contradictory results, it is obvious that a training method cannot be fairly evaluated without consideration of both the rapidity of habit formation and the permanency of the habit. A _priori_ it seems not improbable that slowness of learning should be directly correlated with a high degree of permanency. By the further application of the method which I have used in this study of the efficiency of training we may hope to get a definite answer to this and many other questions concerning the nature of the educative process and the conditions which influence it.
CHAPTER XVI
THE DURATION OF HABITS: MEMORY AND RE-LEARNING
The effects of training gradually disappear. Habits wane with disuse. In the dancer, it is not possible to establish with certainty the existence of memory in the introspective psychological sense; but it is possible to measure the efficiency of the training to which the animal is subjected, and the degree of permanency of habits. The materials which constitute this chapter concern the persistence of unused habits, and the influence of previous training on the re-acquisition of a habit which has been lost or on the acquisition of a new habit. For convenience of description, I shall refer to certain of the facts which are to be discussed as facts of memory, with the clear understanding that consciousness is not necessarily implied. By memory, wherever it occurs in this book, I mean the ability of the dancer to retain the power of adaptive action which it has acquired through training.
I first discovered memory in the dancer, although there was previously no reason for doubting its existence, in connection with the ladder-climbing tests of Chapter XII. In this experiment two individuals which had perfectly learned to escape from the experiment box to the nest-box by way of the wire ladder, when tested after an interval of two weeks, during which they had remained in the nest-box without opportunity to exercise their newly acquired habit, demonstrated their memory of the method of escape by returning to the nest-box by way of the ladder as soon as they were given opportunity to do so. As it did not lend itself readily to quantitative study, no attempts were made to measure the duration of this particular habit. At best the climbing of a wire ladder is of very uncertain value as an indication of the influence of training.
Similarly, the persistence of habits has been forced upon my attention day after day in my various experiments with the mice. It is obvious, then, that the simple fact of memory is well established, and that we may turn at once to an examination of the facts revealed by special memory and re- learning experiments.
The visual discrimination method, which proved invaluable as a means of measuring the rapidity of habit formation, proved equally serviceable in the measurement of the permanency or duration of habits. Memory tests for discrimination habits were made as follows. After a dancer had been trained in the discrimination box so that it could choose the correct electric-box, white, red, blue, or green as it might be, in three successive daily series of ten tests each, it was permitted to remain for a certain length of time without training and without opportunity to exercise its habit of visual discrimination and choice. At the expiration of the rest interval, as we may designate the period during which the habit was not in use, the mouse was placed in the discrimination box under precisely the same conditions in which it had been trained and was given a series of ten memory tests with the box to be chosen alternately on the right and on the left. In order that the entire series of ten tests, and sometimes two such series given on consecutive days, might be available as indications of the duration of a habit, the mouse was permitted to enter and pass through either of the electric-boxes without receiving a shock. Had the shock been given as punishment for a wrong choice, it is obvious that only the first test of the memory series would be of value as an indication of the existence of a previously acquired habit. Even under the conditions of no shock and no stop or hindrance the first test of each memory series is of preeminent importance, for the mouse tends to persist in choosing either the side or the visual condition (sometimes one, sometimes the other) which it chooses in the first test. If the wrong box is chosen to begin with, mistakes are likely to continue because of the lack of punishment; in this case the animal discriminates, but there is no evidence that it remembers the right box. Likewise, if the right electric- box is chosen in the first test, correct choices may continue simply because the animal has discovered that it can safely enter that particular box; again, the animal discriminates without depending necessarily upon its earlier experience. I have occasionally observed a series of ten correct choices, made on the basis of an accidental right start, followed by another series in which almost every choice was wrong, because the animal happened to start wrong.
As the results of my tests of memory are of such a nature that they cannot advantageously be averaged, I have arranged in Table 48 a number of typical measurements of the duration of visual discrimination habits. In this table I have indicated the number and age of the individual tested, the habit of discrimination which had been acquired, the length of the rest interval, the result of the first test (right or wrong), and the number of errors made in each series of ten memory tests.
TABLE 48
MEASUREMENTS OF THE DURATION OF A HABIT
Memory
ERRORS
NO. AGE NAME OF TEST REST FIRST FIRST SECOND INTERVAL CHOICE SERIES SERIES
1000 25 weeks White-black 4 weeks Right 0 5 27 White-black 4 Right 5 7 210 15 White-black 8 Right 5 220 15 White-black 8 Right 4 230 15 White-black 8 Wrong 5 215 15 White-black 8 Right 5 225 15 White-black 8 Right 2 235 15 White-black 8 Right 7 410 15 White-black 8 Wrong 4 415 15 White-black 8 Wrong 6 420 15 White-black 8 Wrong 3 425 15 White-black 8 Right 3 2 28 Black-white 4 Wrong 9 7 17 Black-white 2 Wrong 1 7 21 Black-white 6 Right 1 7 27 Black-white 10 Right 1 6 998 18 Black-white 2 Wrong 3 998 22 Black-white 4 Right 0 998 28 Black-white 10 Right 5 5 13 10 Black-white 4 Right 3 14 10 Black-white 4 Right 3 15 10 Black-white 4 Right 2 16 10 Black-white 4 Right 4 1000 25 Light blue-orange 4 Right 4 2 28 Light blue-orange 2 Wrong 5 5 28 Light blue-orange 6 Wrong 4 6 3 25 Light blue-orange 4 Wrong 8 10 24 Light blue-orange 2 Right 8 10 26 Light blue-orange 2 Right 5 11 25 Light blue-orange 2 Right 6 11 27 Light blue-orange 2 Wrong 5 151 13 Green-red 2 Right 1 0 152 13 Green-red 2 Right 5 1
This quantitative study of the duration of simple habits of choice showed that in the majority of cases a perfectly acquired habit persists for at least two weeks. To be perfectly fair to the animal I must restrict this statement to visual conditions other than colors, for the dancer exhibited little ability either to acquire or to retain a habit of distinguishing spectral colors. Altogether, I made a large number of white-black and black-white memory tests after rest intervals of four, six, eight, or ten weeks. The results for the four-week interval show extreme individual differences in memory. Number 1000, for example, was able to choose correctly every time in a series of white-black tests after a rest interval of four weeks, whereas No. 5 was wrong as often as she was right after the same interval. I have placed the results for these two individuals at the head of the table because they suggest the variations which render averages undesirable. Number 1000 had a perfect habit at the end of four weeks of disuse; No. 5 had no habit whatever. I shall reserve further discussion of age, sex, and individual differences in the permanency of habits for the next chapter.
With Nos. 7 and 998 memory tests were made after three different rest intervals. At the end of two weeks the black-white habit was present in both individuals, although it was not perfect. After six and four weeks, respectively (see Table 48), it still persisted; in fact, it apparently had improved as the result of additional training after the earlier memory tests. At the expiration of ten weeks it had wholly disappeared. In her first series of memory tests after the ten-week interval No. 7 made only one error, but a chance choice of the black (right) in the first test and the subsequent choice of the box in which no shock had been received serve to account for results which at first appear to be indicative of memory. That this explanation is correct is proved by the fact that a second memory series, in which the first choice happened to be wrong, resulted in six mistakes. Evidently she had lost the habit.
In no instance have memory tests definitely indicated the presence of a habit after a rest interval of more than eight weeks. It is safe, therefore, to conclude from the results which have been obtained that a white-black or black-white discrimination habit may persist during an interval of from two to eight weeks of disuse, but that such a habit is seldom perfect after more than four weeks.
The measurements of memory which were made in connection with color discrimination experiments are markedly different from those which were obtained in the brightness tests. As might have been anticipated (?), in view of the extreme difficulty with which the dancer learns to discriminate colors, the habit of discriminating between qualitatively different visual conditions does not persist very long. I have never obtained evidence of a perfect habit after an interval of more than two weeks, and usually, as is apparent from Table 48, the tests indicated very imperfect memory at the end of that interval. It seems probable that even in these so-called color tests discrimination is partly by brightness difference, and that the imperfection of the habit and its short duration are due to the fact that the basis of discrimination is inadequate. This is the only explanation which I have to offer for the difference which has been demonstrated to exist between the duration of brightness discrimination habits and color discrimination habits.
The duration of a discrimination habit having been measured with a fair degree of accuracy, I undertook the task of ascertaining whether training whose results have wholly disappeared, so far as memory tests are in question, influences the re-acquisition of the same habit. Can a habit be re-acquired with greater facility than it was originally acquired? Is re- learning easier than learning? To obtain an answer to the question which may be asked in these different forms, ten individuals were experimented with in accordance with a method whose chief features are now to be stated. In each of these ten individuals a perfect white-black habit was established by the use of the standard series of tests the order of which is given in Table 12. At the expiration of a rest interval of eight weeks precisely the same series of tests were repeated as memory and re-training tests. In this repetition, the preliminary series, _A_ and _B_, served as memory tests, and the subsequent training series, as re-training series.
[Illustration: FIGURE 32.–Error curves plotted from the data given by ten dancers in white-black discrimination tests. The solid line ([Symbol: solid line]) is the error curve of the original learning process; the broken line (——) is that of the re-learning process, after an interval of eight weeks.]
The striking results of this investigation of re-learning are exhibited in the curves of learning and re-learning of Figure 32. These curves make it appear that the mice re-acquired the white-black discrimination habit much more readily than they had originally acquired it. But in addition to furnishing the basis for some such statement as the foregoing, the curves suggest a serious criticism of the experiment.
In the original tests, the preliminary series indicated a strong preference for black. In series _A_ it was chosen on the average 5.8 times in 10, and in series _B_, 5.7 times. This preference was rapidly overcome by the training series, and at the end of 130 tests discrimination was perfect. All this appears in the curve of learning (solid line of figure). On the other hand, these preliminary series when repeated as memory tests, after a rest-interval of eight weeks, gave markedly different results. Series _A_ indicated preference for white (5.6 times in 10) instead of black, and series _B_ indicated only a slight preference for black. In brief, series _A_ and _B_ show that the preference for black was considerably stronger at the beginning of the training than at the beginning of the re-training.
In the light of these facts it is fair to claim that the effects of the white-black training had not wholly disappeared as the result of eight weeks of rest, and that the experiment therefore fails to furnish satisfactory grounds for the statement that re-learning occurs more rapidly than learning. I accept this criticism as pertinent, although not necessarily valid, and at the same time I freely admit that the results have a significance which I had not anticipated. But they are not less interesting or valuable on that account. Granting, then, that at least some of the ten individuals which took part in the experiment had not completely lost the memory of their white-black training at the end of eight weeks, it is still possible that an examination of the individual results may justify some conclusion concerning the question which was proposed at the outset of the investigation. Such an examination is made possible by Tables 49 and 50, in which I have arranged separately the results for the males and the females.
TABLE 49
WHITE-BLACK TRAINING. TEN TESTS PER DAY
Males
TRAINING RETRAINING 210 220 230 410 420 AV. 210 220 230 410 420 AV.
A 6 5 6 6 6 5.8 5 4 5 4 3 4.2 B 6 8 8 5 1 5.6 8 4 5 4 6 5.4
1 6 7 6 2 4 5.0 3 3 4 7 3 4.0 2 4 3 1 2 3 2.6 2 4 2 5 3 3.2 3 3 1 4 3 4 3.0 1 4 1 4 1 2.2 4 5 0 3 3 2 2.6 0 1 0 1 2 0.8 5 3 0 4 1 4 2.4 0 2 0 2 0 0.8 6 2 1 4 0 1 1.6 0 1 0 0 2 0.6 7 1 0 3 1 0 1.0 0 0 0 0 8 0 0 1 0 0 0.2 0 0 1 0.2 9 0 0 0 1 0 0.2 0 0 0 10 0 0 0 0 1 0.2
11 0 0 0 0 0 12 0 0 0 0
13 0 0
14
15
Only three of the ten individuals failed to re-acquire the habit of white- black discrimination more quickly than it had originally been acquired, and, in the case of these exceptions, No. 220 required exactly the same number of tests in each case, and No. 420 was placed at a slight disadvantage in the re-learning series by an interruption of the training between the seventh and the eighth series. Had his training been completed by the sixth series he too would have had the same number of tests in training and re-training. Moreover, and this is of preeminent importance for a fair interpretation of the results, in several instances even those individuals which exhibited as strong a preference for the black in the memory series as in the preliminary series re-learned more quickly than they had learned. Number 210, for example, although he gave no evidence of memory, and, in fact, chose the black more frequently in the memory series than he did in the preliminary series, re-acquired the discrimination habit in less than half the number of tests which had been necessary for the establishment of the habit originally.
TABLE 50
WHITE-BLACK TRAINING. TEN TESTS PER DAY
Females
TRAINING RE-TRAINING 215 225 235 415 425 Av. 215 225 235 415 425 Av. A 8 4 4 8 5 5.8 5 2 7 6 3 4.6 B 8 7 6 6 2 5.8 8 5 6 4 3 5.2 1 7 6 5 6 4 5.6 4 1 5 4 3 3.4 2 5 6 4 2 5 4.4 1 1 1 2 3 1.6 3 3 3 4 3 4 3.4 1 0 3 6 0 2.0 4 2 1 3 3 3 2.4 0 0 3 3 1 1.4 5 1 3 3 3 3 2.6 0 0 died 2 0 0.5 6 2 1 1 1 0 1.0 0 1 0 0.2 7 1 1 2 3 3 2.0 0 0 0
8 0 0 2 2 3 1.4 1 0.2 9 1 0 0 1 1 0.6 0 0
10 0 2 1 0 2 1.0 0 0 11 0 3 0 1 0 0.8 0 0
12 0 0 0 2 0 0.4
13 0 0 0 0 0
14 0 0 0
15 0 0
The facts which have been presented thus far become more significant when the indices of modifiability for the learning and the re-learning processes are compared.
INDICES OF MODIFIABILITY
LEARNING RE-LEARNING
Females . . . . . . . 104 42.5 Males . . . . . . . . 72 54
The behavior of the mice in the experiments, the detailed results of Tables 49 and 50, and the indices of modifiability together justify the following conclusions. Most of the ten dancers, at the end of a rest interval of eight weeks, had so far lost the habit of white-black discrimination that memory tests furnished no conclusive evidence of the influence of previous training; a few individuals seemed to possess traces of the habit after such an interval. In the case of each group of individuals re-training brought about the establishment of a perfect habit far more quickly than did the original training. This suggests the existence of two kinds or aspects of organic modification in connection with training; those which constitute the basis of a definite form of motor activity, and those which constitute the bases or dispositions for the acquirement of certain types of behavior. There are several indications that further study of the modifiability of behavior will furnish the facts which are necessary to render this suggestion meaningful.
Closely related to the facts which have been revealed by the re-training experiments are certain results of the labyrinth experiments. For the student of animal behavior, as for the human educator, it is of importance to learn whether one kind of training increases the efficiency of similar forms of training. Can a dancer learn a given labyrinth path the more readily because it has previously had experience in another form of labyrinth?
The answer to this question, which my experimental results furnish, is given in Table 51. In the upper half of the table have been arranged the results for six individuals which were trained first in labyrinth B, then in labyrinth C, and finally in labyrinth D. Below, in similar fashion, are given the results for six individuals which were trained in the same three labyrinths in the order C, B, D, instead of B, C, D. My purpose in giving the training in these two orders was to ascertain whether labyrinth C, which had proved to be rather difficult for most individuals, would be more easily learned if the training in it were preceded by training in labyrinth C.
TABLE 51
THE INFLUENCE OF ONE LABYRINTH HABIT UPON THE FORMATION OF ANOTHER
LABYRINTH B LABYRINTH C LABYRINTH D NO. OF NO. OF NO. OF NO. OF NO. OF NO. OF NO. FIRST COR- LAST OF FIRST COR- LAST OF FIRST COR- LAST OF RECT TEST FIVE COR- RECT TEST FIVE COR- RECT TEST FIVE COR- RECT TESTS RECT TESTS RECT TESTS
76 8 14 3 19 4 7 78 5 20 6 14 4 5 86 13 22 5 12 3 9 75 4 15 8 19 4 13 77 7 11 11 29 11 12 87 12 22 9 20 4 9
AV. 8.2 17.3 7.0 18.8 5.0 9.2
LABYRINTH C LABYRINTH B LABYRINTH D
58 16 — 2 14 7 10 60 17 — 13 37 10 14 88 25 35 9 22 4 8 49 34 — 1 5 7 8 57 15 — 3 20 3 6 85 11 18 2 11 3 4
AV. 19.7 26.5 5.0 18.2 5.7 8.3
The results are sufficiently definite to warrant the conclusion that experience in B rendered the learning of C easier than it would have been had there been no previous labyrinth training. Those individuals whose first labyrinth training was in C made their first correct trip as the result of 19.7 trials, whereas those which had previously been trained in labyrinth B were able to make a correct trip as the result of only 7.0 trials. Similarly the table shows that training in C rendered the subsequent learning of B easier. To master B when it was the first labyrinth required 8.2 trials; to master it after C had been learned required only 5 trials. In addition to proving that the acquisition of one form of labyrinth habit may facilitate the acquisition of others, comparison of the averages of Table 51 furnishes evidence of the truth of the statement that no results of training can be properly interpreted in the absence of knowledge of the previous experience of the organism.
CHAPTER XVII
INDIVIDUAL, AGE, AND SEX DIFFERENCES IN BEHAVIOR
All dancers are alike in certain important respects, but to the trained observer of animal behavior their individual peculiarities are quite as evident, and even more interesting than their points of resemblance. Omitting consideration of the structural marks of individuality, we shall examine the individual, age, and sex differences in general behavior, rapidity of learning, memory, and discrimination, which have been revealed by my experiments. Observations which bear on the subject of differences are scattered through the preceding chapters, but in no case have they been given sufficient prominence to force them upon the attention of those who are not especially interested in individual peculiarities. It has seemed worth while, therefore, to assemble all the available material in this chapter for systematic examination and interpretation.
In the pages which follow, individual, age, and sex peculiarities are discussed in turn. Within each of these three groups of differences I have arranged in order what Royce has appropriately named the facts of discriminating sensitiveness, docility, and initiative. Individuals of the same age and sex no less than those which differ in sex or age exhibit important differences in ability to discriminate among sense impressions (“discriminative sensitiveness”), in ability to profit by experience (“docility”), and in ability to try new kinds of behavior (“initiative”).
Individual differences in sensitiveness to visual, auditory, tactual, and olfactory stimuli have been revealed by many of my experiments. The brightness discrimination tests conclusively proved that a degree of difference in illumination which is easily detectable by one dancer may be beyond the discriminating sensitiveness of another. Both the tests with gray papers and those with the Weber’s law apparatus furnished striking evidence of individual differences in the kind of visual sensitiveness which throughout this book has been called brightness vision. I suspect that certain of the differences which were observed should be referred to the experience of the individuals rather than to the capacity of the visual organs, for training improves visual discrimination to a much greater extent than would ordinarily be thought possible. To the truth of this statement the results of the Weber’s law experiments with No. 51 bear witness. Likewise in color discrimination there are individual differences, examples of which may be discovered by the examination of the results given in Chapters IX and X.
No differences in auditory sensitiveness appeared in my adult dancers, for in none of them was there definite response to sounds, but among the young individuals differences were prominent. I may call attention to the data on this subject which Table 5, p. 89, contains. The mice in four out of twelve litters gave no indications of hearing any sounds that I was able to produce; the remaining individuals responded with varying degrees of sensitiveness. I made no attempt to measure this sensitiveness, but it obviously differed from mouse to mouse. I feel justified, therefore, in stating that the young dancers exhibit extreme individual difference in sensitiveness to sounds.
My observations of differences in sensitiveness to other forms of stimulation were made in connection with training tests, and although they are not quantitative, I venture to call attention to them. Indeed, I am led by the results of my study of various aspects of the dancer’s behavior to conclude that the race exhibits individual differences in discriminating sensitiveness to a far greater extent than do most mammals, not excepting man. The importance of this fact (for I am confident that any one who carefully examines the detailed results of the various experiments which are described in this book will agree that it is an established fact) cannot be overlooked. It alters our interpretation of the results of training, memory, heredity, and discrimination experiments, and it leads us to suspect that the dancing race is exceedingly unstable. I do not venture to make comparison of my own observations of the dancer’s sense equipment with those of Cyon, Rawitz, Zoth, and Kishi, for the differences are too great in many instances to be thought of as other than species or variety peculiarities. It has seemed fairer to compare only individuals of the same breed, or, as I have done and shall continue to do throughout this chapter, of two lines of descent.
With respect to docility individual differences are prominent. We need only turn to the various tables of results to discover that in modifiability of behavior, in memory, in re-learning, not to mention other aspects of docility, dancers of the same sex and age differed strikingly. Let me by way of illustration cite a few cases of difference in docility. Number 1000 learned to discriminate white from black more quickly and retained his habit longer than any other dancer with which I have experimented. I should characterize him as an exceptionally docile individual. Table 44 offers several examples. Numbers 403 and 407, though they were born in the same litter and were alike in appearance and in conditions of life, acquired the white-black habit with a difference in rapidity which is expressed by the indices of modifiability 50 and 100. In other words, it took No. 407 twice as long to acquire this habit as it took No. 403. Similarly the ladder-climbing tests revealed important individual differences in ability to profit by experience. In the tables of labyrinth tests (38, 39, 40) individual differences are too numerous to mention. It required forty-nine tests to establish in No. 50 a labyrinth-C habit which was approximately equal in degree of perfection to that which resulted from twenty-two tests in the case of No. 52. The figures in this and other instances do not exaggerate the facts, for repeatedly I have tested individuals of the same litter, the same sex, and, so far as I could judge, of the same stage of development, and obtained results which differ as markedly as do those just cited. If space limits permitted, I could present scores of similar differences in docility which the problem, labyrinth, and discrimination methods have revealed.
In examining the detailed individual results of the various tables for differences of this sort, it is important to bear in mind that sex, age, and descent should be taken into account, for with each of them, as will be shown clearly later in this chapter, sensitiveness, docility, and initiative vary. I have therefore based my statements concerning individual differences in docility upon the results of comparison of mice of the same litter, sex, and age. It is safe to say that human beings similarly selected for comparison do not exhibit greater differences in ability to profit by experience than did these dancing mice.
The facts concerning individual differences in initiative which I have discovered are not less definite than those of the preceding paragraphs. From the beginning of my study of the dancer I observed that what one individual would readily learn of his own initiative another never learned. For example, in the ladder-climbing experiment No. 1000 distinguished himself for his initiative, whereas Nos. 4 and 5 never acquired the habit of escaping from confinement by using the ladder. I noticed, in this test of the animal’s ability to learn, that while one individual would be scurrying about trying all ways of escape, investigating its surroundings, looking, sniffing, and dancing by turns, another would devote all its time to whirling, circling, or washing itself. One in the course of its activity would happen upon the way of escape, the other by reason of the limited scope of its activity, not the lack of it, would fail hour after hour to discover even the simplest way of getting back to its nest, to food, and to its companions. Hundreds of times during the past three years I have noticed important individual differences in initiative in connection with the discrimination experiments. The swinging wire doors which one dancer learned to push open before he had been in the box five minutes, another might not become familiar with through his own initiative for hours or days. In fact, it was not seldom that I had to teach an individual to pass from one compartment to the other by gently pushing him against the door until it opened sufficiently to allow him to squeeze through. Occasionally a mouse learned to pull the doors open so that he could pass through the openings in either direction with facility. This was a form of individual initiative which I had not anticipated and did not especially desire, so I did not encourage its development, but, nevertheless, at least one fourth of the mice which I experimented with in the discrimination box learned the trick. The other three fourths, although they were used in the box day after day sometimes for weeks, never discovered that they might return to the nest-box by pulling the swing-door through which they had just passed as well as by entering one of the electric-boxes.
Another indication of individual initiative in action appeared in the tendency of certain mice to climb out of the experiment boxes or labyrinths. It would have been extremely easy for any of the mice to escape from the labyrinths by scaling the walls of the alleys, for they were only 10 cm. in height, and when a dancer stood on its hind legs it could easily reach the top with its nose. But, strange though it will seem to any one who has not worked with the dancer, not more than one in ten of the animals which I observed made any attempt to escape in this manner. They lacked initiative. That it was not due to a lack of the power to climb, I abundantly demonstrated by teaching a few individuals that a scramble in one corner meant easy escape from the maze of paths. I do not think any one of the mice was physically incapable of climbing, but I am confident that they differed markedly, not only in the willingness to try new modes of action, but in the readiness with which they could climb. I have already said that individuals differ noticeably in the scope of their activity. By this statement I mean that they try a varying number of kinds of activity. As in the case of men, so in mice, one individual will do a greater number of things in a few hours than another will in weeks or months. The dancers differ in versatility, in individual initiative, as do we, albeit not so markedly.
Important differences which may with certainty be described as age differences are not so obvious as are such marks of individuality as have been set forth in the preceding pages. I have noted few changes in discriminative sensitiveness, other than those with regard to auditory sensitiveness, which could be correlated with age. In certain instances adults appeared to be able to discriminate more accurately and more easily than young mice, but it is difficult to say whether this change belongs under sensitiveness or docility. I have not made an ontogenetic study of the senses, and I am therefore unable to describe in detail the course of their development and decline. Of one important fact I am certain, that discriminative sensitiveness increases up to a certain point with age and with training.
Differences in docility which are obviously to be correlated with age abound. In the prime of its life (from the second to the tenth month) the dancer is active, full of energy, quick to learn; in its senility (during the second year) it is inactive, but at times even more docile than during the period of greatest physical development. Frequently I have noticed in connection with labyrinth tests that individuals of the age of a year or more learn much more quickly than do individuals of the age of two or three months. But, on the other hand, I have contradictory observations, for now and then I obtained just the opposite result in experiments to test docility. Evidently this is a matter which demands systematic, quantitative investigation. Casual observation may suggest conclusions, but it will not justify them.
Early in my investigation of the behavior of the dancer I conceived the idea of determining the relation of modifiability of behavior (docility) to age. The question which was foremost in my mind and for which I first sought an answer may be stated thus: can the dancer acquire a given habit with the same facility at different ages? Since the visual discrimination experiment seemed to be well suited for the investigation of this problem I planned to train, in the white-black discrimination experiment, five pairs of dancers at the age of one month, and the same number for each of the ages four, seven, ten, thirteen, sixteen, and nineteen months.[1]
[Footnote 1: I have not been able thus far to determine the average length of the dancer’s life. The greatest age to which any of my individuals has attained is nineteen months.]
To test the same individuals month after month would be the ideal way of obtaining an answer to our question, but I could devise no satisfactory way of doing this. The effects of training last so long, as the results of the previous chapter proved, and the uncertainty of their entire disappearance is so serious, that the same training process cannot be used at successive ages. The use of different methods of training is even more unsatisfactory because it is extremely difficult to make accurate quantitative comparison of their results. It was these considerations that forced me to attempt to discover the relation of docility to age by carrying out the same experiments with groups of individuals of different ages.
As my plan involved the execution of precisely the same set of tests with at least seventy individuals whose age, history, and past experience were accurately known, and of which some had to be kept for nineteen months before they could be trained, the amount of labor and the risk of mishap which it entailed were great. To make possible the completion of the investigation within two years, I accumulated healthy individuals for several months without training any of them. In March, 1907, I had succeeded in completing the tests for the age of one month, and I had on hand for the remaining tests almost a hundred individuals, whose ages ranged from a few days to eighteen months. Had everything gone well, the work would have been finished within six months. Suddenly, and without discoverable external cause, my mice began to die of an intestinal trouble, and despite all my efforts to check the disease by changing food supply and environment, all except a single pair died within a few weeks. Thus ended a number of experiments whose final results I had expected to be able to present in this volume. However, the work which I have done is still of value, for the single pair of survivors have made possible the continuance of my tests with other individuals of the same line of descent as those which perished, and I have to regret only the loss of time and labor.
As I have on hand results for ten individuals of the age of one month, and for four individuals of the age of four months, it has seemed desirable to state the problem, method, and incomplete results of this study of the relation of modifiability to age. The indices of modifiability for these two groups of dancers differ so strikingly that I feel justified in persisting in my efforts to obtain comparable data for the seven ages which have been mentioned.
TABLE 52
PLASTICITY (RELATION or MODIFIABILITY TO AGE)
Number of Errors in Successive Daily Series of Ten White-Black Tests, with Dancers Four Months Old
SERIES MALES FEMALES
NO. 76 NO. 78 AV. NO. 75 NO. 77 AV. GENERAL AV.
A 7 7 7.0 4 8 6.0 6.50 B 8 6 7.0 6 5 5.5 6.25
1 5 5 5.0 5 5 5.0 5.00 2 5 4 4.5 2 2 2.0 3.25
3 4 5 4.5 2 5 3.5 4.00 4 3 4 3.5 1 1 1.0 2.25
5 5 2 3.5 0 1 0.5 2.00 6 3 2 2.5 1 0 0.5 1.50
7 2 1 1.5 1 2 1.5 1.50 8 5 1 3.0 0 0 0 1.50
9 1 3 2.0 0 0 0 1.00 10 1 2 1.5 1 0 0.5 1.00 11 1 1 1.0 0 0 0.50
12 1 1 1.0 0 0 0.50 13 0 0 0 0 0 0
14 0 0 0 0
15 0 0 0 0
[Illustration: FIGURE 33.–Plasticity curves. In the left margin are given the indices of modifiability (the number of tests necessary for the establishment of a perfect habit). Below the base line the age of the individuals is given in months. Curve for males, ——–; curve for females, – – – -; curve for both males and females,—-. When these three plasticity curves are completed, they will represent the indices of modifiability as determined for ten individuals at the age of 1 month, and similarly for the same number of individuals at each of the ages, 4, 7, 10, 13, 16, and 19 months.]
The detailed results for the one-month old individuals appear in Table 43; those for the four-month individuals in Table 52. The general averages for the former are to be found in the third column of Table 46, under the heading “10 tests per day”; those for the latter in the last column of Table 52. Mere inspection of these tables reveals the curious sex difference which goes far towards justifying the presentation of this uncompleted work. The index of modifiability for the ten one-month individuals is 88 (that is, 88 tests were necessary for the establishment of a habit); for the four-month individuals it is 102.5. The heavy solid line of Figure 33 joins the points on the ordinates at which these values are located. Apparently, then, the dancer acquires the white-black discrimination habit less readily at the age of four months than at the age of one month.
Further analysis of the results proves that this statement is not true. When the averages for the two sexes are compared, it appears that the males learned much less quickly at four months than at one month, whereas just the reverse is true of the females. The dash and dot line of the figure extends from the index of modifiability of the one-month males (72) to that of the four-month males (120); and the regularly interrupted line similarly joins the indices of the one-month (104) and the four-month (85) females. In seeking to discover age differences in docility or ability to profit by experience we have stumbled upon what appears to be an important sex difference. Perhaps I should add to this presentation of partial results the following statement. Since there are only four individuals in the four-month group, two of each sex, the indices are not very reliable, and consequently too much stress should not be laid upon the age and sex differences which are indicated.
In view of this impressive instance of the way in which averages may conceal facts and lead the observer to false inferences, I wish to remark that my study of the dancer has convinced me of the profound truth of the statement that the biologist, whether he be psychologist, anthropologist, physiologist, or morphologist, should work with the organic individual and should first of all deal with his results as individual results. Averages have their place and value, but to mass data before their individual significance has been carefully sought out is to conceal or distort their meaning. Too many of us, in our eagerness for quantitative results and in our desire to obtain averages which shall justify general statements, get the cart before the horse.
Figure 33 presents the beginning of what I propose to call plasticity curves. When these three curves are completed on the basis of experiments with five dancers of each sex for each of the ages indicated on the base line of the figure, they will indicate what general changes in plasticity, modifiability of behavior, or ability to learn (for all of these expressions have been used to designate much the same capacity of the organism) occur from the first month to the nineteenth in the male and the female dancer, and in the race without respect to sex. So far as I know, data for the construction of plasticity curves such as I hope in the near future to be able to present for the dancing mouse have not been obtained for any mammal.
At present it would be hazardous for me to attempt to state any general conclusion concerning the relation of docility to age.
The initiative of the dancer certainly varies with its age. In scope the action system rapidly increases during the first few months of life, and if the animal be subjected to training tests, this increase may continue well into old age. The appearance of noticeable quiescence does not necessarily indicate diminished initiative. Frequently my oldest mice have shown themselves preeminent in their ability to adjust their behavior to new conditions. However, I have not studied individuals of more than eighteen months in age. One would naturally expect initiative to decrease in senility. All that I can say is that I have seen no indications of it.
We may now briefly consider the principal sex differences which have been revealed by the experiments. In sensitiveness I have discovered no difference, but it should be stated that no special attention has been given to the matter. In docility the males usually appeared to be superior to the females. This was especially noticeable early in my visual discrimination tests. The males almost invariably acquired a perfect habit quicker than the females. I may cite the following typical instances. Number 14 acquired the black-white habit with 40 tests; No. 13, with 60 (Table 10, p. 109). Of the five pairs of individuals whose records in white-black training appear in Table 43, not one contradicts the statement which has just been made. It is to be noted, however, that under certain conditions of training, for example, 20 tests per day, the female is at an advantage. Recently I have with increasing frequency obtained measures of docility which apparently favor the female. That this difference in the results is due to a difference in age is probable.
In labyrinth tests the female is as much superior to the male as the male is to the female in discrimination tests. From the tables of Chapter XIII I may take a few averages to indicate the quantitative nature of this difference. A degree of proficiency in labyrinth B attained by the males after 7.0 trials was equaled by the females after 6.2 trials. In labyrinth C the males acquired a habit as a result of 18.7 trials; the females, as a result of 13.8. And similarly in labyrinth D, 6.1 trials did no more for the males than 5.9 did for the females.
That at the age of about one month the male dancer should be able to acquire a visual discrimination habit more rapidly than the female, whereas the female can acquire a labyrinth habit more readily than the male, suggests an important difference in the nature of their equipment for habit formation. One might hazard the suggestion that the male depends more largely upon discrimination of external conditions, whereas the female depends to a greater extent than does the male upon the internal, organic changes which are wrought by acts. At any rate the female seems to follow a labyrinth path more mechanically, more accurately, more easily, and with less evidence of sense discrimination than does the male.
Finally, in concluding this chapter, I may add that in those aspects of behavior which received attention in the early chapters of this volume the dancers differ very markedly. Some climb readily on vertical or inclined surfaces to which they can cling; others seldom venture from their horizontally placed dance floor. Some balance themselves skillfully on narrow bridges; others fall off almost immediately. My own observations, as well as a comparison of the accounts of the behavior of the dancer which have been given by Cyon, Zoth, and other investigators, lead me to conclude that there are different kinds of dancing mice. This may be the result of crosses with other species of mice, or it may be merely an expression of the variability of an exceptionally unstable race.
I can see no satisfactory grounds for considering the dancer either abnormal or pathological. It is a well-established race, with certain peculiarities to which it breeds true; and no pathological structural conditions, so far as I have been able to learn, have been discovered.
I have presented in this chapter on differences a program rather than a completed study. To carry out fully the lines of work which have been suggested by my observations and by the presentation of results would occupy a skilled observer many months. I have not as yet succeeded in accomplishing this, but my failure is not due to lack of interest or of effort.
CHAPTER XVIII
THE INHERITANCE OF FORMS OF BEHAVIOR
In a general way those peculiarities of behavior which suggested the name dancing mouse are inherited. Generation after generation of the mice run in circles, whirl, and move the head restlessly and jerkily from side to side. But these forms of behavior vary greatly. Some individuals whirl infrequently and sporadically; others whirl frequently and persistently, at certain hours of the day. Some are unable to climb a vertical surface; others do so readily. Some respond to sounds; others give no indications of ability to hear. I propose in this chapter to present certain facts concerning the inheritance of individual peculiarities of behavior, and to state the results of a series of experiments by which I had hoped to test the inheritance of individually acquired forms of behavior.
My study of the nature of the whirling tendency of the dancer has revealed the fact that certain individuals whirl to the right almost uniformly, others just as regularly to the left, and still others now in one direction, now in the other. On the basis of this observation, the animals have been classified as right, left, or mixed whirlers. Does the dancer transmit to its offspring the tendency to whirl in a definite manner?
Records of the direction of whirling of one hundred individuals have been obtained. For twenty of these mice the determination was made by counting the number of complete turns in five-minute intervals at six different hours of the day. For the remaining eighty individuals the direction was discovered by observation of the activity of the animals for a brief interval at five different times. Naturally, the former results are the more exact; in fact, they alone have any considerable quantitative value. But for the problem under consideration all of the determinations are sufficiently accurate to be satisfactory.
The distribution of the individuals which were examined as to direction of whirling is as follows.
RIGHT WHIRLERS LEFT WHIRLERS MIXED WHIRLERS TOTAL
Males 19 19 12 50
Females 12 23 15 50
The frequency of occurrence of left whirlers among the females is unexpectedly high. Is this to be accounted for in terms of inheritance? In my search for an answer to this question I followed the whirling tendency from generation to generation in two lines of descent. These two groups of mice have already been referred to as the 200 line and the 400 line. The former were descended from Nos. 200 and 205, and the latter from Nos. 152 and 151. Individuals which resulted from the crossing of these lines will be referred to hereafter as of mixed descent. There were some striking differences in the behavior of the mice of the two lines of descent. As a rule the individuals of the 200 line climbed more readily, were more active, danced less vigorously, whirled less rapidly and less persistently, and were in several other respects much more like common mice than were the individuals of the 400 line. It is also to be noted (see Table 5) that few of the litters of the 200 line exhibited auditory reactions, whereas almost all of the litters of the 400 line which were tested gave unmistakable evidence of sensitiveness to certain sounds. These differences at once suggest the importance of an examination of the whirling tendency of each line of descent.
The results for the several generations of each line which I had opportunity to examine are unexpectedly decisive so far as the question in point is concerned.
INDIVIDUALS OF THE 200 LINE
MALES FEMALES
First generation No. 200, ? No. 205, ? Second generation No. 210, Mixed whirler No. 215, Left whirler Third generation No. 220, Mixed whirler No. 225, Mixed whirler Fourth generation No. 230, Right whirler No. 235, Mixed whirler Fifth generation No. 240, Right whirler No. 245, Left whirler
INDIVIDUALS OF THE 400 LINE
MALES FEMALES
First generation No. 152, Left whirler No. 151, Left whirler Second generation No. 410, Left whirler No. 415, Right whirler Third generation No. 420, Left whirler No. 425, Left whirler
One line of descent exhibited no pronounced whirling tendency; the other exhibited a strong tendency to whirl to the left. Are these statements true for the group of one hundred individuals whose distribution among the three classes of whirlers has been given? In order to obtain an answer to this question I have reclassified these individuals according to descent and direction of whirling.
INDIVIDUALS OF THE 200 LINE
RIGHT WHIRLERS LEFT WHIRLERS MIXED WHIRLERS TOTAL
Males 7 6 8 21 Females 5 8 8 21 12 14 16 42
INDIVIDUALS OF THE 400 LINE
RIGHT WHIRLERS LEFT WHIRLERS MIXED WHIRLERS TOTAL
Males 4 9 1 14 Females 6 9 4 19
10 18 5 33
INDIVIDUALS OF MIXED DESCENT
9 10 6 25
Three interesting facts are indicated by these results: first, the inheritance of a tendency to whirl to the left in the 400 line of descent; second, the lack of any definite whirling tendency in the 200 line; and third, the occurrence of right and left whirlers with equal frequency as a result of the crossing of these two lines of descent.
It is quite possible, and I am inclined to consider it probable, that the pure dancer regularly inherits a tendency to whirl to the left, and that this is obscured in the case of the 200 line by the influences of a cross with another variety of mouse. It is to be noted that the individuals of the 200 line were predominantly mixed whirlers, and I may add that many of them whirled so seldom that they might more appropriately be classed as circlers.
THE INHERITANCE OF INDIVIDUALLY ACQUIRED FORMS OF BEHAVIOR
The white-black discrimination experiments which were made in connection with the study of vision and the modifiability of behavior were so planned that they should furnish evidence of any possible tendency towards the inheritance of modifications in behavior. The problem may be stated thus. If a dancing mouse be thoroughly trained to avoid black, by being subjected to a disagreeable experience every time it enters a black box, will it transmit to its offspring a tendency to avoid black?
Systematic training experiments were carried on with individuals of both the 200 and 400 lines of descent. For each of these lines a male and a female were trained at the age of four weeks to discriminate between the white and the black electric-boxes and to choose the former. After they had been thoroughly trained these individuals were mated, and in course of time a male and female, chosen at random from their first litter, were similarly trained. All the individuals were trained in the same way and under as nearly the same conditions as could be maintained, and accurate records were kept of the behavior of each animal and of the number of errors of choice which it made in series after series of tests. What do these records indicate concerning the influence of individually acquired forms of behavior upon the behavior of the race?
TABLE 53
THE INHERITANCE OF THE HABIT OF WHITE-BLACK DISCRIMINATION
Number of Errors in Daily Series of Ten Tests
MALES FEMALES
SERIES FIRST SECOND THIRD FOURTH FIRST SECOND THIRD FOURTH GENERA- GENERA- GENERA- GENERA- GENERA- GENERA- GENERA- GENERA- TION TION TION TION TION TION TION TION
No. 210 No. 220 No. 230 No. 240 No. 215 No. 225 No. 235 No. 245
A 6 5 6 7 8 4 4 7 B 6 8 8 8 8 7 6 5
1 6 7 6 5 7 6 5 4 2 4 3 1 5 5 6 4 5 3 3 1 4 5 3 4 4 3 4 5 0 3 4 2 1 3 1 5 3 0 4 2 1 3 3 0 6 2 1 4 2 2 1 1 1 7 1 0 3 1 1 1 2 0 8 0 0 1 0 0 0 2 3 9 0 0 0 1 1 0 0 0 10 0 0 1 0 2 1 1 11 0 0 0 3 0 0 12 0 0 0 0 0
13 0 0 0 0 14 0
I have records for four generations in the 200 line and for three generations in the 400 line.[1] As the results are practically the same for each, I shall present the detailed records for the former group alone. In Table 53 are to be found the number of errors made in successive series of ten tests each by the various individuals of the 200 line which were trained in this experiment. The most careful examination fails to reveal any indication of the inheritance of a tendency to avoid the black box. No. 240, in fact, chose the black box more frequently in the preference series than did No. 210, and he required thirty more tests for the establishment of a perfect habit than did No. 210. Apparently descent from individuals which had thoroughly learned to avoid the black box gives the dancer no advantage in the formation of a white-black discrimination habit. There is absolutely no evidence of the inheritance of this particular individually acquired form of behavior in the dancer.
[Footnote 1: This experiment was interrupted by the death of the animals of both lines of descent.]
INDEX
Abnormal dancers.
Acquired forms of behavior.
Act, useless, repeated.
Activity, periods of.
Affirmation, choice by.
Age, peculiarities;
maximum age;
and intelligence.
Albino cat;
dog.
Alexander and Kreidl, young dancer; behavior;
tracks of mice;
behavior in cyclostat;
behavior of white mouse and dancer; structure of ear;
deafness.
Allen, G. M., drawing of dancer;
heredity in mice.
Alleys, width of, in labyrinths.
Amyl acetate for photometry.
Anatomy of dancer.
Animals, education of.
Appuun whistles.
Audition. _See_ Hearing.
Averages, dangers in.
Baginsky, B., model of ear of dancer. Bateson, W., breeding experiments.
Behavior, of dancer;
inheritance of;
when blinded;
equilibration;
dizziness;
structural bases of;
of young;
changes in;
useless acts;
under experimental conditions;
in indiscriminable conditions;
value of sight;
in labyrinth experiments;
modifiability of;
history of;
explanations of;
individual differences in.
Blinded dancers, behavior of.
Blue-orange tests;
blue-red tests;
blue-green tests;
blue-green blindness.
Bradley papers.
Brain, structure of.
Breeding of dancers.
Brehm, A. E., “Tierleben”.
Brightness vision;
preference;
check experiments;
relation to color vision.
Cages for dancers.
Candle meter.
Candle power.
Cardboards, for tests of vision;
positions of.
Care of dancer.
Castle, W. E., drawing of mouse;
cages.
Cat, albino;
training of.
Cerebellum of dancer.
Characters, acquired.
Check experiments.
China, dancers of.
Choice, exhibition of;
by affirmation;
by negation;
by comparison;
methods of.
Circling, a form of dance.
Circus course mice.
Cleghorn, A. G.
Climbing of dancer.
Cochlea, functions of.
Color blindness.
Color discrimination apparatus.
Colored glasses.
Colored papers.
Color patterns of dancers.
Color vision, problem;
methods of testing;
tests with colored papers,
tests with ray filters,
orange-blue tests,
yellow-red tests,
light blue-orange tests,
dark blue-red tests,
green-light blue tests,
violet-red tests,
green-blue tests,
green-red tests,
blue-green tests,
blue-red tests,
structure of the retina,
conclusions,
of different animals,
Comparative pedagogy,
Comparison, choice by,
Cones, lacking in eye of dancer,
Corti, organ of, in dancer,
Cotton mouse,
Curves, of habit formation,
irregularities of,
of labyrinth habit,
of discrimination habit,
of learning and re-learning,
of plasticity,
Cyclostat, behavior of dancer in,
Cyon, E. de, dancer pathological,
behavior,
behavior of blinded dancers,
varieties of dancer,
space perception,
individual differences,
anatomy of dancer,
hearing of dancer,
pain cries.
Dancers, occurrence among common mice, varieties of,
hybrid,
Dancing,
forms of dance movement,
whirling, circling, figure-eights, manege movements, solo dance, centre dance,
direction of,
periods of,
amount of,
causes of,
sex differences in,
individual differences in,
Darbishire, A. D., breeding experiments with dancers, Deafness of dancer,
causes of,
Descent, lines of,
Development of young dancer,
Differences, individual,
sex,
Direction of movement, choice by,
Direction of whirling,
Discrimination, visual, box,
of brightness,
white-black and black-white,
of grays,
habits,
by odor,
by form,
method,
habit defined,
Diseases of dancer,
Dizziness,
visual,
rotational,
Docility,
Dog, albino,
training of,
fear of electric shock.
Ear, structure of,
structural types,
model of,
of rabbit,
functions of,
movements of,
Educability of dancer,
Education, human,
methods of,
of vision,
Efficiency of training,
Electric-box for visual tests,
Electric-labyrinth for habit experiments, Electric-shock as punishment for mistakes, Epidemic among dancers,
Equilibration in dancer,
Error curves,
form of,
Error records versus time records,
Errors, in labyrinths,
nature of,
types of,
value of,
number of,
Even numbers to designate males,
Excitability of dancer,
Experience, value of,
influence of,
Eyes, of dancer
opening of
retina of
Fear, in dancer
Females,
designated by odd numbers
dancing of
voice of
_See_ Sex
Fighting of dancers
Figure eight dance
Filters for obtaining colored light Food of dancer
Form discrimination
Frog,
reactions of
repetition of act by
Functions of eye
Galton whistle
Gestation, period of, in dancer
Gray papers
Green blue tests
Green-red tests
Grouping for averages
Guaita, G von,
breeding experiments with dancers
Haacke, W,
description of dancer,
origin of dancer
breeding experiments
Habit,
of dancing,
discrimination,
useless
labyrinth,
duration of,
reacquisition of,
relations of,
Habit formation,
and the senses,
_versus_ habit performance,
in the dancer and in the common mouse, curves of,
speed of
Habituation to sounds
Hacker, dancing shrews
Hair, appearance of
Hamilton, G V, experiments with dog Hatai, S, the dancer
Head, shape of, in dancer
Hearing,
in dancer
in young
in adult
methods of testing,
in frog
Hefner unit of light
Heredity
_See_ Inheritance
Hering, E, colored papers
History,
of dancer
of acts
Hunger as motive in experiments
Hybrid dancers
Imitation in dancer
Index of modifiability
Individuality
Inheritance
Inhibition of an act
Initiative of dancer
Insight of dancer
Intelligence,
measures of,
comparisons
Interrupted circuit for experimental use Irregular labyrinths
Janssen-Hoffman spectroscope
Japan, dancers in
Judgment in dancer
Kammerer, P, dancing wood mice,
Kishi, K,
dancer in Japan
origin of race,
equilibration,
blinded dancer,
structure of ear,
wax in ears,
tests of hearing
Koenig tuning forks,
steel bars
Kreidl, A
_See_ Alexander
Labyrinth,
forms of,
labyrinth A,
errors in,
tests,
labyrinth B,
tests,
labyrinth C,
labyrinth D,
a standard labyrinth,
regular and irregular labyrinths
Labyrinth errors and individual tendencies Labyrinth habits,
Labyrinth method,
Labyrinth path, formula,
method of recording,
Ladder climbing tests,
Landois, H, account of dancer,
Lathrop, A, dancers,
Learning, process,
methods of in dancer,
by being put through act,
by imitation,
by rote,
rapidity of,
permanency of,
learning and relearning,
curves of,
Left whirlers,
Life span of dancer,
Light, reflected,
transmitted, unit of measurement,
control of,
Litter, size of, in dancer,
Lummer-Brodhun photometer.
Males, dancing of,
fighting and killing young, designation of, voice of, _See_ Sex
Manege movements,
Mark, E L, cages,
Maze _See_ Labyrinth
Measurements, of light,
of rapidity of habit formation,
of intelligence,
of efficiency of training,
Memory, defined,
for ladder climbing,
tests of,
measurements of,
span of,
for brightness,
for color,
Method, of studying dance,
for testing hearing,
indirect,
for testing vision,
motives,
for brightness vision,
for color vision,
of shifting filters,
of testing form discrimination,
of testing Weber’s law,
development of methods,
of choice,
food box,
labyrinth,
of recording errors,
of training
problem method, labyrinth method, discrimination method, of recording labyrinth path,
qualitative versus quantitative,
of studying senses,
values of methods,
of measuring intelligence,
quantitative,
comparisons of,
Milne-Edwards, origin of dancer,
Mitsukun, K, the dancer in Japan,
Mixed whirlers,
Modifiability, of behavior,
of useless acts,
index of,
Motives, for activity,
for choice,
avoidance of discomfort,
in labyrinths,
desire to escape, to get food, to avoid pain, Motor, tendencies,
ability,
capacity
Movements,
of ears,
_Mus musculus L_,
_Mus spiciosus L_,
_Mus sylvaticus L_.
_Nankin nesumi_, name for dancer,
Negation, choice by,
Nendel, R, gray papers,
Nerve, eighth,
Nervous system,
Nest materials,
Noises, effects of,
Numbers, odd for females, even for males, reference, _See_ Bibliographic List.
Odors, discrimination by,
Old Fancier’s description of dancer, Olfactory sense _See_ Smell
Orange-blue tests,
Orientation of dancer,
Origin of dancer;
by selectional breeding;
by inheritance of an acquired character; by mutation;
by pathological changes;
by natural selection.
Panse, R.,
structure of ear;
explanation of deafness.
Papers, Nendel’s grays;
Bradley’s colored;
Hering’s colored.
Parker, G. H.
Path in labyrinth, record of.
Pathological condition of dancer.
Pedagogy, comparative.
Perception,
of brightness;
of color;
of movement;
of form.
Peru, dancers in.
Petromyzon, semicircular canals of. Photometer, Lummer-Brodhun.
Plasticity of dancer;
curves of.
Position choice by,
of cardboards.
Preference for brightness,
tests of.
Preliminary tests.
Probable error.
Problems, of structure;
of method.
Punishment versus reward.
Putting-through, training by.
Qualitative methods.
Quantitative methods.
Rabbit, ear of.
Rawitz, B., behavior of dancer;
structure of ear;
deafness of dancer;
hearing in young.
Ray filters.
Reactions, to sounds;
to disagreeable stimuli;
valueless.
Reasoning, implicit.
Reconstruction method.
Records, of markings of dancers;
of time;
of errors;
of path.
Red, stimulating value of;
vision.
Reference numbers to literature.
_See_ Literature on Dancer.
Reflected light.
Refrangibility and vision of dancer. Regular labyrinth.
Re-learning, relation to learning;
curves of.
Reliability of averages.
Repetition of useless acts.
Rest-interval.
Restlessness, of dancer;
cause of.
Retina of dancer.
Retzius, ear of rabbit.
Reward, for performance of act;
versus punishment.
Right whirlers;
behavior in labyrinth;
occurrence of;
inheritance of tendency.
Rods of retina.
Rotational dizziness.
Rubber stamps of labyrinths.
Saint-Loup, R.
Schlumberger, C.;
wood carving with dancers.
Selenka, ear of rabbit.
Semicircular canals.
Sense organs.
Senses, and habit formation;
differences in.
Sensitiveness
Sex, recognition of, designation
of, peculiarities
Shellac to coat cards
Shrews, dancing
Sight, role of, _See_ Vision,
Brightness Vision, and Color Vision Smell sense of, in labyrinth habits
Sniffing by dancer
Solutions as ray filters
_Sorex vulgaris L_
Sound, reactions to
Space perception
Spectroscope
Spectrum, stimulating value of
Standard, candle, light,
labyrinth
Stine, W M, photometrical measurements Strength of dancer
Structure, of brain,
of ear, of eye
Swinhoe, mice in China
Temperament of animal
Temperature sense
Tests, visual, number of,
per day,
Threshold of discrimination
Time records
Touch, and labyrinth habits
Training conditions of, Weber’s
law, methods of,
and retraining, in labyrinths,
efficiency of, two test,
ten-test, twenty-test,
continuous, relation to
methods, spread of
Transmitted light.
Variability of dancer,
Variable light.
Varieties of dancer
Violet red tests
Vision, brightness
vision, color vision,
training of, importance
of, conclusions concerning
Visual dizziness
Voice of dancer
Watson, J B, habit formation
Waugh, K, color vision apparatus,
retina of mouse
Wax, plugs of, in ear of mouse
Weber’s law, tests of, apparatus
Weldon, W F R, breeding experiments, Whirling of dancer
Yellow Red tests
Young dancers, killing of, by male, description of, development
of, hearing of, intelligence
of, size of
Zoth, O, origin of dancer, size
of young mice, the senses of
dancer, behavior, dancing,
equilibration, climbing
dancers, individual differences,
tests of hearing,
vision