Part 19 (1/2)
On November 20, Nos. 4 and 5 were placed in the wooden box and left there for half an hour. As they had failed to escape at the end of this interval, they were taken out of the box by the experimenter and returned to the nest-box. November 21 and 22 this test of their ability to learn to climb the ladder was repeated with the same result. On November 23 they were placed in the box with the three mice which had previously been trained to climb the ladder. The latter escaped at once. Apparently the attention of Nos. 4 and 5 was drawn to the ladder by the disappearance of their companions, for they approached its foot and No. 5 climbed up a short distance. Neither succeeded in escaping, however, and they made no further efforts that day. On the 24th, and daily thereafter until the 29th, these two dancers were placed in the box for half an hour, with negative results. At the end of the half hour on the 29th, Nos. 2 and 6 were placed in the box and permitted to go back and forth from one box to the other repeatedly within sight of Nos. 4 and 5. The latter made no attempts to follow them, although at times they seemed to be watching their movements as they ascended the ladder.
To render the results of this test of imitation still more conclusive No.
5 was given further opportunity to learn from No. 1000. Beginning December 2, the following method of experimentation was employed with these two individuals. They were placed in the wooden box together. No. 1000 usually climbed out almost immediately. Sometimes No. 5 apparently saw him disappear up the ladder; sometimes she paid no attention whatever either to the presence or absence of her companion. After he had been in the nest-box for a few seconds, No. 1000 was returned to the wooden box by the experimenter and again permitted to climb out for the benefit of No. 5.
This mode of procedure was kept up until No. 1000 had made from three to ten trips. No. 5 was left in the box for half an hour each day. This test was repeated on 18 days within a period of 3 weeks. No. 5 showed no signs of an imitative tendency, and she did not learn to climb the ladder.
To this evidence of a lack of an imitative tendency in the dancer I may here add the results of my observations in other experiments. In the discrimination tests and in the labyrinth tests I purposely so arranged conditions, in certain instances, that one individual should have an opportunity to imitate another. In no case did this occur. Seldom indeed did the animals so much as follow one another with any considerable degree of persistence. They did not profit by one another's acts.
Excellent evidence in support of this conclusion was furnished by the behavior of the mice in the discrimination experiments. Some individuals learned to pull as well as to push the swinging wire doors of the apparatus and were thus enabled to pa.s.s through the doorways in either direction; other individuals learned only to pa.s.s through in the direction in which the doors could be pushed open. Naturally I was interested to discover whether those which knew only the trick of opening the doors by pus.h.i.+ng would learn to pull the doors or would be stimulated to try by seeing other individuals do so. At first I arranged special tests of imitation in the discrimination box; later I observed the influence of the behavior of one mouse upon that of its companion in connection with visual discrimination experiments. This was made possible by the fact that usually a pair of individuals was placed in the discrimination box and the tests given alternately to the male and to the female. Both individuals had the freedom of the nest-box and each frequently saw the other pa.s.s through the doorway between the nest-box, _A_, and the entrance chamber, _B_ (Figure 14), either from _A_ to _B_ by pus.h.i.+ng the swing door or from _B_ to _A_ by pulling the door.
Although abundant opportunity for imitation in connection with the opening of the doors in the discrimination box was given to twenty-five individuals, I obtained no evidence of ability to learn by imitation. The dancers did not watch the acts which were performed by their companions, and in most instances they did not attempt to follow a mate from nest-box to entrance chamber.
These problem tests, simple as they are, have revealed two important facts concerning the educability of the dancer. First, that it does not learn by imitation to any considerable extent, and, second, that it is aided by being put through an act. Our general conclusion from the results of the experiments which have been described in this chapter, if any general conclusion is to be drawn thus prematurely, must be that the dancing mouse in its methods of learning differs markedly from other mice and from rats.
CHAPTER XIII
HABIT FORMATION: THE LABYRINTH HABIT
The problem method, of which the ladder and door-opening tests of the preceding chapter are examples, has yielded interesting results concerning the individual initiative, ingenuity, motor ability, and ways of learning of the dancer; but it has not furnished us with accurate measurements of the rapidity of learning or of the permanency of the effects of training.
In this chapter I shall therefore present the results of labyrinth experiments which were planned as means of measuring the intelligence of the dancer.
The four labyrinths which have been used in the investigation may be designated as _A, B, C,_ and _D_. They differ from one another in the character of their errors, as well as in the number of wrong choices of a path which the animal might make on its way from entrance to exit. In the use of the labyrinth method, as in the case of the discrimination method of earlier chapters, the steps by which a satisfactory form of labyrinth for testing the dancer was discovered are quite as interesting and important for those who have an intelligent appreciation of the problems and methods of animal psychology as are the particular results which were obtained. For this reason, I shall describe the various forms of labyrinth in the order in which they were used, whether they proved satisfactory or not. At the outset of this part of my investigation, it was my purpose to compare directly the capacity for habit formation in the dancer with that of the common mouse. This proved impracticable because the same labyrinth is not suited to the motor tendencies of both kinds of mice.
[Ill.u.s.tration: FIGURE 25.--Labyrinth A. _I_. entrance; _O_, exit; 1, 2, 3, 4, blind alleys.]
The first of the four labyrinths, A, appears in ground plan in Figure 25.
It was constructed of wood, as were the other labyrinths also, and measured 60 cm. in length and width, and 10 cm. in depth. The outside alleys were 5 cm. wide. In the figure, _I_ marks the starting point or entrance to the maze, and _O_ the exit through which the mouse was permitted to pa.s.s into its nest-box. Any turn in the wrong direction which the animal made in its progress from entrance to exit was recorded as an error. The four errors, exclusive of the mistake of turning back, which were possible in this labyrinth, are indicated in the figure by the numerals 1, 2, 3, and 4. By retracing its steps a mouse might repeat any one or all of these errors, and add to them the error of turning back.
In the experiments a mouse was permitted to enter the maze from a small box which had been placed by the experimenter at _I_, and an accurate record was kept of the number of errors which it made in finding its way from entrance to exit, and of the time occupied. Each of five dancers was given 31 tests in this labyrinth. The number of tests per day varied, as is indicated in Table 36, from 1 to 4. The results of the tests, so far as errors and times are in question, appear in the table. _T_ at the head of a column is an abbreviation for time, _E_ for errors.
The dancers did not learn to escape from this labyrinth easily and quickly. In fact, the average time of the thirty-first test (198”) is considerably longer than that of the first (130”). The number of errors decreased, it is true, but even for the last test it was 6.6 as compared with only a little more than twice that number for the first test. The last column of the table furnishes convincing proof of the truth of the statement that the animals did not acquire a perfect labyrinth-A habit.
Was this due to inability to learn so complex a path, or to the fact that the method is not adapted to their nature? Observation of the behavior of the mice in the experiments enables me to say with certainty that there was no motive for escape sufficiently strong to establish a habit of following the direct path. Often, especially after a few experiences in the maze, a dancer would wander back and forth in the alleys and central courts, dancing much of the time and apparently exploring its surroundings instead of persistently trying to escape. This behavior, and the time and error results of the accompanying table, lead me to conclude that the labyrinth method, as it has been employed in the study of the intelligence of several other mammals, is not a satisfactory test of the ability of the dancer to profit by experience. That the fault is not in the labyrinth itself is proved by the results which I obtained with common mice.
TABLE 36
RESULTS OF LABYRINTH A TESTS WITH DANCERS
AVERAGE TEST DATE No. 1000 No. 2 No. 6 No. 4 No. 5 FOR ALL 1905 T E T E T E T E T E T E
1 Nov 23 130” 14 100” 8 170” 13 60” 6 190” 26 130” 13.4 2 24 140 19 78 7 60 8 149 6 211 25 128 13.0 3 25 392 31 87 1 98 5 185 13 120 9 176 11.8 4 26 448 38 38 3 47 2 50 3 121 12 141 11.3 5 27 142 8 21 2 27 3 27 2 17 1 47 3.2 6 28 45 2 61 7 63 5 102 8 33 4 61 5.2 7 29 303 17 64 7 36 3 42 2 57 4 100 6.6 8 30 222 15 26 2 37 5 42 3 7 0 67 5.0 9 Dec 1 185 9 36 5 48 3 63 3 94 8 85 5.6 10 2 52 2 71 4 19 0 196 5 95 11 87 4.4 11 3 180 8 32 2 107 4 52 3 38 4 82 4.2 12 4 310 10 133 11 65 3 242 6 125 6 175 7.2 13 4 153 9 335 55 130 10 195 15 154 18 193 21.4 14 5 330 7 69 2 42 2 201 6 130 10 154 5.4 15 5 287 7 34 4 61 4 136 7 25 2 109 4.8 16 5 455 15 65 4 25 0 110 8 160 15 183 8.4 17 6 120 15 280 9 33 0 168 4 39 2 128 6.0 18 6 120 4 164 10 81 4 101 5 85 4 110 5.4 19 6 132 12 78 7 110 6 40 2 151 12 102 7.8 20 7 258 10 223 16 33 1 92 5 37 1 129 6.6 21 7 110 7 23 3 44 4 20 4 305 23 100 8.2 22 7 100 4 60 8 167 15 44 7 58 4 86 7.6 23 8 43 1 179 7 356 6 34 3 65 3 135 4.0 24 8 92 5 56 5 42 3 17 1 23 1 46 3.0 25 9 85 5 114 3 62 3 129 8 31 0 84 3.8 26 9 30 2 36 4 109 15 12 1 34 2 44 4.8 27 9 69 5 40 4 85 6 36 3 16 1 49 3.8 28 10 169 7 80 3 28 0 142 5 35 2 89 3.4 29 10 155 5 266 8 91 5 27 0 37 2 115 4.0 30 10 29 1 25 2 124 14 83 6 111 12 74 7.0 31 10 465 6 208 8 95 3 65 3 159 13 198 6.6