Sixteen Experimental Investigations from the Harvard Psychological Laboratory by Hugo Münsterberg (100 books to read .txt) 📕

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Experiments were made under uniform conditions, as follows. A subject

was taken from the aquarium and placed in a dry jar for about five

minutes, in order to increase the desire to return to the water; it

was then put into the triangular space of the experiment box and

allowed to find its way to the aquarium. Only one choice of direction

was necessary in this, namely, at the opening where one of the

passages was closed. That the animal should not be disturbed during

the experiment the observer stood motionless immediately behind the

box.

Before the glass plate was introduced a preliminary series of tests

was made to see whether the animals had any tendency to go to one side

on account of inequality of illumination, of the action of gravity, or

any other stimulus which might not be apparent to the experimenter.

Three subjects were used, with the results tabulated.

Exit by Exit by

Right Passage Left Passage.

No. 1 6 4

No. 2 7 3

No. 3 3 7

16 14

Since there were more cases of exit by the right-hand passage, it was

closed with the glass plate, and a series of experiments made to

determine whether the crawfish would learn to avoid the blocked

passage and escape to the aquarium by the most direct path. Between

March 13 and April 14 each of the three animals was given sixty

trials, an average of two a day. In Table I. the results of these

trials are arranged in groups of ten, according to the choice of

passages at the exit. Whenever an animal moved beyond the level of the

partition (P) on the side of the closed passage the trial was

counted in favor of the closed passage, even though the animal turned

back before touching the glass plate and escaped by the open passage.

TABLE I.

HABIT FORMATION IN THE CRAWFISH.¹

Experiments. No. 1 No. 2 No. 3 Totals Per cent

Open Closed Open Closed Open Closed Open Closed Open

1-10 8 2 5 5 2 8 15 15 50.0

11-20 4 6 8 2 6 4 18 12 60.0

21-30 6 3² 8 2 8 2 22 7 75.8

31-40 9 1 8 2 8 2 25 5 83.3

41-50 8 2 8 2 7 3 23 7 76.6

51-60 10 0 8 2 9 1 27 3 90.0

TEST OF PERMANENCY OF HABIT AFTER 14 DAYS’ REST.

61-70 6 4 8 2 8 2 22 8 73.3

(1-10)

71-80 6 4 8 2 7 3 21 9 70.0

(11-20)

¹The experiments of this table were made by F.D. Bosworth.

²One trial in which the subject failed to return to the water

within thirty minutes.

In these experiments there is a gradual increase in the number of

correct choices (i.e., choice of the ‘open’ passage) from 50 per

cent. for the first ten trials to 90 per cent. for the last ten

(trials 51-60). The test of permanency, made after two weeks, shows

that the habit persisted.

Although the observations just recorded indicate the ability of the

crawfish to learn a simple habit, it seems desirable to test the

matter more carefully under somewhat different conditions. For in the

experiments described the animals were allowed to go through the box

day after day without any change in the floor over which they passed,

and as it was noted that they frequently applied their antennae to the

bottom of the box as they moved along, it is possible that they were

merely following a path marked by an odor or by moistness due to the

previous trips. To discover whether this was really the case

experiments were made in which the box was thoroughly washed out after

each trip.

The nature of the test in the experiments now to be recorded is the

same as the preceding, but a new box was used. Fig. 2 is the floor

plan and side view of this apparatus. It was 44.5 cm. long, 23.5 cm.

wide and 20 cm. deep. The partition at the exit was 8.5 cm. in length.

Instead of placing this apparatus in the aquarium, as was done in the

previous experiments, a tray containing sand and water was used to

receive the animals as they escaped from the box. The angle of

inclination was also changed to 7°. For the triangular space in which

the animals were started in the preceding tests a rectangular box was

substituted, and from this an opening 8 cm. wide by 5 cm. deep gave

access to the main compartment of the box.

[Illustration: FIG. 2. Floor Plan and Side View of Labyrinth Number 2.

E, entrance chamber from which animal was started; C, cloth

covering E; M, mirror; T, tray containing sand and water; G,

glass plate; P, partition; R, right exit passage; L, left exit

passage. Scale 1/8.]

A large healthy crawfish was selected and subjected to tests in this

apparatus in series of ten experiments given in quick succession. One

series a day was given. After each test the floor was washed; as a

result the experiments were separated from one another by a

three-minute interval, and each series occupied from thirty minutes to

an hour. Table II. gives in groups of five these series of ten

observations each. The groups, indicated by Roman numerals, run from

I. to IX., there being, therefore, 450 experiments in all. Groups I.

and II., or the first 100 experiments, were made without having either

of the exit passages closed, in order to see whether the animal would

develop a habit of going out by one side or the other. It did very

quickly, as a matter of fact, get into the habit of using the left

passage (L.). The last sixty experiments (Groups I. and II.) show not

a single case of escape by the right passage. The left passage was now

closed. Group III. gives the result. The time column (i.e., the

third column of the table) gives for each series of observations the

average time in seconds occupied by the animal in escaping from the

box. It is to be noted that the closing of the Left passage caused an

increase in the time from 30.9 seconds for the last series of the

second group to 90 seconds for the first series of the third group. In

this there is unmistakable evidence of the influence of the change in

conditions. The animal after a very few experiences under the new

conditions began going to the Right in most cases; and after 250

experiences it had ceased to make mistakes. Group VII. indicates only

one mistake in fifty choices.

TABLE II.

HABIT FORMATION AND THE MODIFICATION OF HABITS IN THE CRAWFISH.

Results in Series of Ten. Avs. in Groups of 50.

Series L. R. Time. L. R. L. R. Time.

Group I. 1 9 1 45 Per Cent.

2 3 7 69

3 9 1 20

4 4 6 72

5 10 31

— —

35 15 70 30 47.4

II. 1 10 29

2 10 30

3 10 30

4 10 28.8

5 10 30.9

— –-

50 100 30

…. ….

III. 1 4 6 90 2

2 2 8 89.2 1

3 1 9 36.7 1

4 2 8 51 2

5 1 9 43 2

— — —

10 40 7 20 80 62

…. ….

IV. 1 3 7 124 1

2 2 8 44 5

3 2 8 37 4

4 10 34

5 2 8 1

— — —

9 41 11 18 82 60

…. ….

V. 1 10 44 2

2 10 35 4

3 3 7 76 3

4 2 8 50 7

5 1 9 50 4

— — —

6 44 20 12 88 51

…. ….

VI. 1 2 8 45 2

2 10 41 5

3 1 9 41.8 7

4 10 32.7 7

5 10 8

— — —

3 47 29 6 94 40

…. ….

VII. 1 1 9 39 4

2 10 38 7

3 10 30.7 3

4 10 42 6

5 10 48 4

— — —

1 49 24 2 98 39.5

R. L.

…. ….

VIII. 1 8 2 147 1

2 9 1 26

3 8 2 49 2

4 9 1 38 2

5 9 1 41

— — —

43 7 5 86 14 60.2

…. ….

IX. 1 1 9 41

2 2 8 39 1

3 10 29

4 1 9 47

5 1 9 32 1 10 90 38

— — —

5 45 2

The dotted lines at the beginning of groups indicate the closed passage.

At the beginning of Group VIII. the Right instead of the Left passage

was closed in order to test the ability of the animal to change its

newly formed habit. As a result of this change in the conditions the

animal almost immediately began going to the Left. What is most

significant, however, is the fact that in the first trial after the

change it was completely confused and spent over fifteen minutes

wandering about, and trying to escape by the old way (Fig. 4

represents the path taken). At the end of the preceding group the time

of a trip was about 48 seconds, while for the first ten trips of Group

VIII. the time increased to 147 seconds. This remarkable increase is

due almost entirely to the great length of time of the first trip, in

which the animal thoroughly explored the whole of the box and made

persistent efforts to get out by the Right passage as it had been

accustomed to do. It is at the same time noteworthy that the average

time for the second series of Group VIII. is only 26 seconds.

For Group IX. the conditions were again reversed, this time the Left

passage being closed. Here the first trial was one of long and careful

exploration, but thereafter no more mistakes were made in the first

series, and in the group of fifty tests there were only five wrong

choices.

The fifth column, R. L. and L. R., of Table II. contains cases in

which the subject started toward one side and then changed its course

before reaching the partition. In Group III., for instance, when the

Left passage was closed, the subject started toward the Left seven

times, but in each case changed to the Right before reaching the

partition. This is the best evidence of the importance of vision that

these experiments furnish.

The first experiments on habit formation proved conclusively that the

crawfish is able to learn. The observations which have just been

described prove that the labyrinth habit is not merely the following

of a path by the senses of smell, taste or touch, but that other

sensory data, in the absence of those mentioned, direct the animals.

So far as these experiments go there appear to be at least four

sensory factors of importance in the formation of a simple labyrinth

habit: the chemical sense, touch, vision and the muscle sense. That

the chemical sense and touch are valuable guiding senses is evident

from even superficial observation, and of the importance of vision and

the muscle sense we are certain from the experimental evidence at

hand.

[Illustration: FIG. 3. Path taken by crawfish while being trained to

avoid the left passage. Marks along the glass plate and partition

indicate contact by the antennae and chelæ.]

Of the significance of the sensations due to the ‘direction of

turning’ in these habits the best evidence that is furnished by this

work is that of the following observations. In case of the tests of

Table II. the subject was, after