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

with it, and it was as comfortable a habitat as could conveniently be

arranged. Usually the animals moved about almost constantly until they

succeeded in getting out, but now and then one would remain inactive

for long intervals; for this reason no record of the time taken for

escape was kept. On account of the great amount of time required by

experiments of this kind I have been unable to repeat this series of

experiments in toto on several animals in order to get averages, but

what is described for a representative individual has been proved

normal by test observations on other animals. There are very large

individual differences, and it may well be that the subject of the

series of experiments herein described was above the average in

ability to profit by experience. But, however that may be, what is

demonstrated for one normal frog is thereby proved a racial

characteristic, although it may be far from the mean condition.

Before beginning training in the labyrinth, preliminary observations

were made to discover whether the animals had any tendencies to go

either to the right or to the left. When the colored cardboards were

removed it was found that there was usually no preference for right or

left. In Table I. the results of a few preliminary trials with No. 2

are presented. For these the colors were used, but a tendency to the

right shows clearly. Trials 1 to 10 show choice of either the right or

the red throughout; that it was partly both is shown by trials 11 to

30, for which the colors were reversed. This individual has therefore,

to begin with, a tendency to the right at the entrance. At the exit it

went to the right the first time and continued so to do for several

trials, but later it learned by failure that there was a blocked

passage as well as an open one. In the tables the records refer to

choices. It was useless to record time or to lay much stress upon the

course taken, as it was sometimes very complicated; all that is given,

therefore, is the action in reference to the passages. Right in

every case refers to the choice of the open way, and wrong to the

choice of the blocked passage. The paths taken improved steadily in

that they became straighter. A few representative courses are given in

this report. Usually if the animal was not disturbed a few jumps

served to get it out of the labyrinth.

TABLE I.

PRELIMINARY TRIALS WITH FROG NO. 2.

Trials. Red on Right. White on Left.

1 to 10 10 times to red 0

Red on Left. White on Right.

11 to 20 4 times to red 6

Red on Left. White on Right.

21 to 30 3 times to red 7

To Red. To White. To Right. To Left.

Totals. 17 13 23 7

This table indicates in trials 1 to 10 a strong tendency to the red

cardboard. Trials 21 to 30 prove that there was also a tendency to the

right.

Training was begun with the labyrinth arranged as shown in Fig. 1,

that is, with the left entrance passage and the right exit passage

open, and with red cardboard on the right (red was always on the side

to be avoided) and white on the left. Table II. contains the results

of 110 trials with No. 2, arranged according to right and wrong choice

at the entrance and exit. Examination of this table shows a gradual

and fairly regular increase in the number of right choices from the

first series to the last; after 100 experiences there were practically

no mistakes.

With another subject, No. 6a, the results of Table III. were

obtained. In this instance the habit formed more slowly and to all

appearances less perfectly. Toward the end of the second week of work

6a showed signs of sickness, and it died within a few weeks, so I do

not feel that the experiments with it are entirely trustworthy. During

the experiments it looked as if the animal would get a perfectly

formed habit very quickly, but when it came to the summing up of

results it was obvious that there had been little improvement.

[Illustration: FIG. 2. Labyrinth as arranged for experiments. E,

entrance; R, R, regions covered with red; W, W, regions covered

with white. The tracing represents the path taken by No. 2 on the

sixth trial. Dots mark jumps.]

TABLE II.

LABYRINTH HABIT. FROG NO. 2.

Entrance. Exit. Remarks.

Trials. Right. Wrong. Right. Wrong.

1-10 1 9 4 6

One day rest.

11-20 2 8 5 5

21-30 4 6 7 3

31-40 5 5 6 4

41-50 5 5 6 2

(17) (33) (30) (20)

51-60 9 1 8 2

61-70 6 4 10 0

71-80 7 3 9 1

81-90 9 1 8 2

91-100 10(50) 0(10) 10(52) 0( 8)

– – – –

67 43 82 28

Other animals which were used gave results so similar to those for

frog No. 2 that I feel justified in presenting the latter as

representative of the rapidity with which the green frog profits by

experience.

TABLE III.

LABYRINTH HABIT. FROG NO. 6a.

Entrance. Exit. Remarks.

Trials Right. Wrong. Right. Wrong.

1-10 6 4 5 5

One day rest.

11-20 7 3 4 6

21-30 2 8 1 9

31-40 6 4 1 9

41-50 7 3 8 2

(28) (22) (19) (31)

51-60 5 5 7 3

61-70 6 4 4 6

71-80 4 6 3 7

One day rest.

81-90 5 5 7 3

91-100 10(30) 0(20) 8(29) 2(21)

–- –- –- –-

(58) (44) (48) (52)

Preliminary Trials.

Red on Left Partition at Exit on Right

1-5 5 times to Red 4 times to Partition.

Red on Right Partition at Exit on Left

6-10 3 times to Red 5 times to Partition.

2. Rapidity of Habit Formation.—As compared with other vertebrates

whose rapidity of habit formation is known, the frog learns slowly.

Experimental studies on the dog, cat, mouse, chick and monkey furnish

excellent evidence of the ability of these animals to profit quickly

by experience through the adapting of their actions to new conditions.

They all show marked improvement after a few trials, and after from

ten to thirty most of them have acquired perfect habits. But the

comparison of the frog with animals which are structurally more

similar to it is of greater interest and value, and we have to inquire

concerning the relation of habit formation in the frog to that of

fishes and reptiles. Few experimental studies with these animals have

been made, and the material for comparison is therefore very

unsatisfactory. E.L. Thorndike[1] has demonstrated the ability of

fishes to learn a labyrinth path. In his report no statement of the

time required for the formation of habit is made, but from personal

observation I feel safe in saying that they did not learn more quickly

than did the frogs of these experiments. Norman Triplett[2] states

that the perch learns to avoid a glass partition in its aquarium after

repeatedly bumping against it. Triplett repeated Moebius’ famous

experiment, and found that after a half hour’s training three times a

week for about a month, the perch would not attempt to capture minnows

which during the training periods had been placed in the aquarium with

the perch, but separated from them by a glass partition. Triplett’s

observations disprove the often repeated statement that fishes do not

have any associative processes, and at the same time they show that

the perch, at least, learns rapidly—not so rapidly, it is true, as

most animals, but more so in all probability than the amphibia.

[1] Thorndike, Edward: ‘A Note on the Psychology of Fishes,’

American Naturalist. 1899, Vol. XXXIII., pp. 923-925.

[2] Triplett, Norman: ‘The Educability of the Perch,’ _Amer.

Jour. Psy._, 1901, Vol. XII., pp. 354-360.

The only quantitative study of the associative processes of reptiles

available is some work of mine on the formation of habits in the

turtle.[3] In the light of that study I can say that the turtle learns

much more rapidly than do fishes or frogs. Further observations on

other species of turtles, as yet unpublished, confirm this conclusion.

[3] Yerkes, Robert Mearns: ‘The Formation of Habits in the

Turtle,’ Popular Science Monthly, 1901, Vol. LVIII., pp.

519-535.

For the frog it is necessary to measure and calculate the improvement

in order to detect it at first, while with the turtle or chick the

most casual observer cannot fail to note the change after a few

trials. In connection with the quickness of the formation of

associations it is of interest to inquire concerning their permanency.

Do animals which learn slowly retain associations longer? is a

question to which no answer can as yet be given, but experiments may

readily be made to settle the matter. I have tested the frog for

permanency, and also the turtle, but have insufficient data for

comparison.

3. Sensory Data Contributing to the Associations.—Among the most

important of the sensory data concerned in the labyrinth habit are the

visual impressions received from the different colored walls, the

slight differences in brightness of illumination due to shadows from

the partitions and the contrast in form of the two sides of the

labyrinth resulting from the use of the partitions, and the muscular

sensations dependent upon the direction of turning. The experiments

proved beyond question that vision and the direction of turning were

the all-important factors in the establishment of the habit. At first

it seemed as if the direction of turning was the chief determinant,

and only by experimenting with colors under other conditions was I

able to satisfy myself that the animals did notice differences in the

appearance of their surroundings and act accordingly. In Table IV.

some results bearing on this point have been arranged. To begin with,

the habit of going to the left when the red was on the right at the

entrance had been established; then, in order to see whether the

colors influenced the choice, I reversed the conditions, placing the

red on the left, that is, on the open-passage side. The results as

tabulated in the upper part of Table IV. show that the animals were

very much confused by the reversal; at the entrance where there were

several guiding factors besides the colors there were 50 per cent. of

mistakes, while at the exit where there were fewer differences by

which the animal could be directed it failed every time. This work was

not continued long enough to break up the old habit and replace it by

a new one, because I wished to make use of the habit already formed

for further experiments, and also because the animals remained so long

in the labyrinth trying to find their way out that there was constant

danger of losing them from too prolonged exposure to the dry air.

TABLE IV.

INFLUENCE OF CHANCES OF CONDITIONS. FROG NO. 2.

Habit perfectly formed of going to Left (avoiding Red) at

entrance and to Right at exit. Conditions now reversed. Red on

Left. Partition at Exit on Right.

Trials. Entrance. Exit. Remarks.

Right. Wrong. Right. Wrong.

1-5 3 2 0 5

6-10 2 3 0 5

Discontinued because animal remained so long in labyrinth that

there was danger of injuring it for further work. This shows

that the habit once formed is hard to change.

Given 20 trials with conditions as at first in order to

establish habit again.

1-10 9 1 8 2

11-20 10 0 9 1

Colors reversed, no other change. To test influence of colors.