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The Dancing Mouse

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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




On the basis of two tests per day, two common mice, a white one and a gray
one, quickly learned to escape from labyrinth _A_ by the shortest path.
The time of escape for the gray individual (Table 37) decreased from 180"
in the first test to 21" in the tenth, and the number of errors from 6 to
1. Similarly in the case of the white individual, the time decreased from
122" to 8", and the errors from 5 to 1. A fraction of the number of tests
to which the dancer had been subjected sufficed to establish a habit of
escape in the common mouse. It is evident, therefore, that the dancer
differs radically from the common mouse in its behavior in a maze, and it
is also clear that the labyrinth method, if it is to be used to advantage,
must be adapted to the motor tendencies of the animal which is to be
tested.



TABLE 37

RESULTS OF LABYRINTH A TESTS WITH COMMON MICE

GREY MOUSE WHITE MOUSE
TEST T E T E

1 180" 6 122" 5
2 26 2 80 6
3 37 1 56 4
4 18 0 27 1
5 68 2 33 2
6 10 1 19 1
7 11 1 17 1
8 13 1 17 1
9 10 0 8 1
10 21 1 8 1



The behavior of the dancer made obvious two defects in labyrinth A. Its
passages are so large that the mouse is constantly tempted to dance, and
it lacks the basis for a strong and constant motive of escape by the
direct path. To obviate these shortcomings labyrinth B was constructed, as
is shown in Figures 23 and 24, with very narrow passages, and a floor
which was covered with the wires of an interrupted electric circuit so
that errors might be punished. The length of this labyrinth was 52 cm. and
the passages were 2.5 cm. wide and 10 cm. deep. Dancing in these narrow
alleys was practically impossible, for the mice could barely turn around
in them. In the case of all except the common mice and two dancers, a
depth of 10 cm. was sufficient to keep the animals in the maze without the
use of a cover.

As an account of the behavior of the dancer in labyrinth B has already
been given in Chapter XI, I may now state the general results of the
experiments. In all, thirty individuals were trained in this labyrinth.
Each individual was given tests at the rate of one per minute until it had
succeeded in following the correct path five times in succession. The weak
electric shock, which was given as a punishment for mistakes, provided an
activity-impelling motive for escape to the nest-box.

An idea of the extreme individual difference in the rapidity with which
the labyrinth-B path was learned by these dancers may be obtained by an
examination of Table 38, from which it appears that the smallest number of
training tests necessary for a successful or errorless trip through the
maze was one and the largest number fourteen. It is to be remembered that
each mouse was given an opportunity to pass through the labyrinth once
without punishment for errors, and thus to discover, before the training
tests were begun, that a way of escape existed. This first test we may
designate as the preliminary trial. Table 38 further indicates that the
females acquired the labyrinth habit more quickly than did the males.



TABLE 38

RESULTS OF LABYRINTH-B EXPERIMENTS, WITH TWENTY DANCERS


MALES FEMALES

NO. OF NO. OF FIRST NO. OF LAST OF NO. OF NO. OF FIRST NO. OF LAST OF
MOUSE CORRECT FIVE CORRECT MOUSE CORRECT FIVE CORRECT
TEST TESTS TEST TESTS

76 8 14 75 4 15
78 5 20 77 7 11
86 13 22 87 12 22
58 2 14 49 1 5
50 6 23 57 3 20
60 13 37 59 14 28
410 6 20 415 4 13
220 4 8 225 6 18
212 3 7 211 6 10
214 10 28 213 5 14

AV. 7.0 19.3 AV. 6.2 15.6




A graphic representation of certain of the important features of the
process of formation of the labyrinth-B habit is furnished by Figure 26 in
which the solid line is the curve of learning for the ten males of Table
38, and the broken line for the ten females. These two curves were plotted
from the number of errors made in the preliminary trial (P in the figure)
and in each of the subsequent tests up to the sixteenth. In the case of
both the males and the females, for example, the average number of errors
in the preliminary trial was 11.3, as is indicated by the fact that the
curves start at a point whose value is given in the left margin as 11.3.
In the second training test the number of errors fell to 3.3 for the males
and 2.7 for the females. The number of the test is to be found on the base
line; the number of errors in the left margin. If these two curves of
learning were carried to their completion, that for the males would end
with the thirty-seventh test, and that for the females with the twenty-
eighth.

[Illustration: FIGURE 26.--Curves of habit formation, plotted from the
data of labyrinth-B tests with ten males and ten females. The figures in
the left margin indicate the number of errors; those below the base line
the number of the test. _P_ designates the preliminary test. Males
____[solid line]; Females ----[broken line].]

Time records are not reported for these and subsequent labyrinth tests
because they proved to be almost valueless as measures of the rapidity of
habit formation. At any point in its progress through a labyrinth, the
dancer may suddenly stop to wash its face, look about or otherwise examine
its surroundings; if a shock be given to hurry it along it may be
surprised into an error. It is my experience, and this is true of other
animals as well as of the dancing mouse, that a long trip, as measured in
time units, does not necessarily indicate the lack of ability to follow
the labyrinth path correctly and rapidly. Hence, whenever it is possible
(and the experimenter can always plan his tests so that it shall be
possible), the number of errors should be given first importance and the
time of the test second place. I have presented in Table 38 the number of
the first correct test, and the number of the last of five successive
correct tests. Space cannot be spared for records of the errors made in
the several tests by each individual.

In general, labyrinth B proved very satisfactory as a means of testing the
ability of the dancer to learn a simple path. The narrow passages
effectively prevented dancing, and the introduction of the electric shock
as a punishment for mistakes developed a motive for escape which was
uniform, constant, and so strong that the animals clearly did their best
to escape from the labyrinth quickly and without errors. This maze was so
simple that it did not tend to discourage them as did the one which is
next to be described. It must be admitted, however, that, though labyrinth
B is perfectly satisfactory as a test of the dancer's ability to learn to
follow a simple path, it is not an ideal means of measuring the rapidity
of habit formation. This is due to the fact that the preliminary trial and
the first training test play extremely different roles in the case of
different individuals. A dancer which happens to follow the correct path
from entrance to exit in the preliminary trial may continue to do so, with
only an occasional error, during several of the early training tests, and
it may therefore fail for a considerable time to discover that there are
errors which should be avoided. The learning process is delayed by its
accidental success. On the other hand, an individual which happens to make
many mistakes to begin with immediately attempts to avoid the points in
the maze at which it receives the electric shock. I was led to conclude,
as a result of the labyrinth-B experiments, that the path was too easy,
and that a more complex labyrinth would, in all probability, furnish a
more satisfactory means of measuring the rapidity of habit formation.

[Illustration: FIGURE 27--A record sheet, showing the plan of labyrinth C
(as made on the sheet by means of a rubber stamp) on which the
experimenter recorded the path followed by the mouse. This sample sheet
presents the path records for the first, fifth, tenth, and eleventh tests
of No. 2 in labyrinth C. 1, 2, 3, 4, 5 designate the several errors of the
labyrinth.]

On the basis of the supposition that a maze whose path was so complex that
the animal would not be likely to follow it correctly in the early trials
would be more to the purpose than either A or B, labyrinth C was devised.
As is shown in the plan of this maze, Figure 27, five mistakes in choice
of path were possible on the forward trip. These errors, as a rule, were
more difficult for the dancers to avoid than those of labyrinths A and B.
Those which are designated by the numerals 2, 3, and 4 were especially
difficult. Error 4 was much more troublesome for left whirlers than for
right whirlers because, after turning around abruptly at the entrance to
the blind alley, the former type of dancer almost always followed the side
wall of the maze so far that it missed the correct path. Undoubtedly the
various errors are not of the same value for different individuals; but it
would be extremely difficult, if not impossible, to devise a maze which
should be equally difficult for several normal individuals.

In order that records of the path followed by a mouse in test after test
might be kept with ease and accuracy by the experimenter, the plan of this
labyrinth, and also that of labyrinth D, were cast in rubber. The outlines
of labyrinths C and D which appear in Figures 27 and 28 respectively were
made with the rubber stamps which were thus obtained. Figure 27 is the
reproduction of a record sheet which presents the results of the first,
the fifth, the tenth, and the eleventh tests of No. 2 in labyrinth C. The
path followed by this individual in the first test was far too complex to
be traced accurately on the record sheet. The record therefore represents
merely the number of errors which was made in each region of the maze. For
the fifth test, and again for the tenth and the eleventh, the path was
recorded accurately. This simple device for making record blanks which can
readily be filled in at the time of the experiment should recommend itself
to all students of animal behavior.

In labyrinth C ten pairs of dancers were given continuous training tests
at the rate of one test per minute until they were able to follow the
direct path correctly. Because of the difficulty in learning this maze
perfectly, it was not demanded of the mice that they should follow the
path correctly several times in succession, but instead the training was
terminated after the first successful trip.



TABLE 39

RESULTS OF LABYRINTH-C EXPERIMENTS, WITH TWENTY DANCERS


MALES FEMALES

NO. OF NO. OF FIRST NO. OF NO. OF FIRST
MOUSE CORRECT TEST MOUSE CORRECT TEST

2 11 29 15
30 33 49 34
50 49 57 15
52 22 59 15
58 16 215 10
60 17 415 10
76 3 75 8
78 6 77 11
86 5 87 9
88 25 85 11

AV. 18.7 AV. 13.8




The results of the experiments with this labyrinth as they are presented
in Table 39 indicate that its path is considerably more difficult for the
dancer to learn than that of labyrinth B, that the females learn more
quickly than the males, and finally, that individual differences are just
as marked as they were in the case of the simpler forms of labyrinth. It
therefore appears that increasing the complexity of a labyrinth does not,
as I had supposed it might, diminish the variability of the results.
Certain of the individual differences which appear in Table 39 are due,
however, to the fact that in some cases training in labyrinth B had
preceded training in labyrinth C, whereas in the other cases C was the
first labyrinth in which the animals were tested. But even this does not
serve to account for the wide divergence of the results given by No. 2 and
No. 50, for the latter had been trained in B previous to his training in
C, and the former had not been so trained. Yet, despite the advantage
which previous labyrinth experience gave No. 50, he did not learn the path
of C as well in fifty tests as No. 2 did in eleven. The facts concerning
the value of training in one form of labyrinth for the learning of
another, as they were revealed by these experiments, may more fittingly be
discussed in a later chapter in connection with the facts of memory and
re-learning.

[Illustration: FIGURE 28.--Plan of Labyrinth _D_, as reproduced from a
print made with a rubber stamp. _I_, entrance; _O_, exit; numerals 1 to
13, errors.]

Labyrinth C is a type of maze which might properly be described as
irregular, since the several possible errors are extremely different in
nature. In view of the results which this labyrinth yielded, it seemed
important that the dancer be tested in a perfectly regular maze of the
labyrinth-D type. The plan which I designed as a regular labyrinth has
been reproduced, from a rubber stamp print, in Figure 28. As is true also
of the mazes previously described, it provides four kinds of possible
mistakes: namely, by turning to the left (errors 1, 5, 9, and 13), by
turning to the right (errors 3, 7, and 11), by moving straight ahead
(errors 2, 4, 6, 8, 10, and 12), and by turning back and retracing the
path just followed. The formula for the correct path of _D_ is simple in
the extreme, in spite of the large number of mistakes which are possible,
for it is merely "a turn to the right at the entrance, to the left at the
first doorway, and thereafter alternately to the right and to the left
until the exit is reached." This concise description would enable a man to
find his way out of such a maze with ease. Labyrinth D had been
constructed with an exit at 10 so that it might be used as a nine-error
maze if the experimenter saw fit, or as a thirteen-error maze by the
closing of the opening at 10. In the experiments which are now to be
described only the latter form was used.

Can the dancer learn a regular labyrinth path more quickly than an
irregular one? Again, I may give only a brief statement of results. Each
of the twenty dancers, of Table 40, which were trained in labyrinth D had
previously been given opportunity to learn the path of C, and most of them
had been trained also in labyrinth B. All of them learned this regular
path with surprising rapidity. The numerical results of the tests with
labyrinths B, C, and D, as well as the behavior of the mice in these
several mazes, prove conclusively that the nature of the errors is far
more important than their number. Labyrinth D with its thirteen chances of
error on the forward trip was not nearly as difficult for the dancer to
learn to escape from as labyrinth C with its five errors. That the
facility with which the twenty individuals whose records are given in
Table 40 learned the path of D was not due to their previous labyrinth
experience rather than to the regularity of the maze is proved by the
results which I obtained by testing in D individuals which were new to
labyrinth experiments. Even in this case, the number of tests necessary
for a successful trip was seldom greater than ten. If further evidence of
the ease with which a regular labyrinth path may be followed by the dancer
were desired, it might be obtained by observation of the behavior of an
individual in labyrinths C and D. In the former, even after it has learned
the path perfectly, the mouse hesitates at the doorways from time to time
as if uncertain whether to turn to one side or go forward; in the latter
there is seldom any hesitation at the turning points. The irregular
labyrinth is followed carefully, as by choice of the path from point to
point; the regular labyrinth is followed in machine fashion,--once
started, the animal dashes through it.



TABLE 40

RESULTS OF LABYRINTH-D EXPERIMENTS, WITH TWENTY DANCERS


MALES FEMALES

NO. OF NO. OF FIRST NO. OF LAST OF NO. OF NO. OF FIRST NO. OF LAST OF
MOUSE CORRECT TWO CORRECT MOUSE CORRECT TWO CORRECT
TEST TESTS TEST TESTS

2 3 7 29 10 11
58 7 10 49 7 8
30 9 10 57 3 6
60 10 14 215 6 10
402 10 11 415 7 8
76 4 7 75 4 13
78 4 5 77 11 12
86 3 9 87 4 9
88 4 8 85 3 4
90 7 8 83 4 7

Av. 6.1 8.9 Av. 5.9 8.8




From the results of these labyrinth experiments with dancers I am led to
conclude that a standard maze for testing the modifiability of behavior of
different kinds of animals should be constructed in conformity with the
following suggestions. Errors by turning to the right, to the left, and by
moving forward should occur with equal frequency, and in such order that
no particular kind of error occurs repeatedly in succession. If we should
designate these three types of mistake by the letters _r, l_, and _s_
respectively, the error series of labyrinth C would read _l-l-r-s-l_. It
therefore violates the rule of construction which I have just formulated.
In the case of labyrinth D the series would read _l-s-r-s-l-s-r-s-l-s-r-s-
l_. This also fails to conform with the requirement, for there are three
errors of the first type, four of the second, and six of the third. Again,
in a standard maze, the blind alleys should all be of the same length, and
care should be taken to provide a sufficiently strong and uniform motive
for escape. In the case of one animal the desire to escape from
confinement may prove a satisfactory motive; in the case of another, the
desire for food may conveniently supplement the dislike of confinement;
and in still other cases it may appear that some form of punishment for
errors is the only satisfactory basis of a motive for escape. Readers of
this account of the behavior of the dancing mouse must not infer from my
experimental results that the electric shock as a means of forcing
discrimination will prove satisfactory in work with other animals or even
with all other mammals. As a matter of fact it has already been proved by
Doctor G. van T. Hamilton that the use of an electric shock may so
intimidate a dog that experimentation is rendered difficult and of little
value. And finally, in connection with this discussion of a standard
Labyrinth, I wish to emphasize the importance of so recording the results
of experiments that they may be interpreted in terms of an animal's
tendency to turn to the right or to the left. My work with the dancer has
clearly shown that the avoidance of a particular error may be extremely
difficult for left whirlers and very easy for right whirlers.

I hope I have succeeded in making clear by the foregoing account of my
experiments that the labyrinth method is more satisfactory in general than
the problem method as a means of measuring the rapidity of habit formation
in the dancer, and I hope that I have made equally clear the fact that it
is very valuable as a means of discovering the roles of the various senses
in the acquirement of a habit (Chapter XI). From my own experience in the
use of the labyrinth with the dancer and with other animals, I am forced
to conclude that its chief value lies in the fact that it enables the
experimenter so to control the factors of a complex situation that he may
readily determine the importance of a given kind of sense data for the
formation or the execution of a particular habit. As a means of measuring
the intelligence of an animal, of determining the facility with which it
is capable of adjusting itself to new environmental conditions, and of
measuring the permanency of modifications which are wrought in its
behavior by experimental conditions, I value the labyrinth method much
less highly now than I did previous to my study of the dancer. It is
necessarily too complex for the convenient and reasonably certain
interpretation of results. Precisely what is meant by this statement will
be evident in the light of the results of the application of the
discrimination method to the dancer, which are to be presented in the next
chapter. The labyrinth method is an admirable means of getting certain
kinds of qualitative results; it is almost ideal as a revealer of the role
of the senses, and it may be used to advantage in certain instances for
the quantitative study of habit formation and memory. Nevertheless, I
think it may safely be said that the problem method and the discrimination
method are likely to do more to advance our knowledge of animal behavior
than the labyrinth method.




CHAPTER XIV

HABIT FORMATION: THE DISCRIMINATION METHOD

Discrimination is demanded of an animal in almost all forms of the problem
and labyrinth methods, as well as in what I have chosen to call the
discrimination method. In the latter, however, discrimination as the basis
of a correct choice of an electric-box is so obviously important that it
has seemed appropriate to distinguish this particular method of measuring
the intelligence of the dancer from the others which have been used, by
naming it the discrimination method.

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