Various - Harvard Psychological Studies, Volume 1

V >> Various >> Harvard Psychological Studies, Volume 1

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55

We thus return to the simple line. I have considered a series of
judgments on it, and a series on two different figures, varying in the
degree of complexity presented, in one of their fillings. It remains
very briefly to see if the introspection on the simple line furnishes
further warrant for carrying the complexities over into the simple
line and so giving additional validity to the outlined theory of
substitution. The following phrases are from introspective notes.

_A_. Sweep wanted over long part. More attention to short.
Significance of whole in short. Certainly a concentration of interest
in the short. Short is efficacious. Long means rest; short is the
center of things. Long, an effortless activity; short, a more
strenuous activity. When complex fillings are introduced, subject is
helped out; does not have to put so much into the short division. In
simple line, subject _introduces_ the concentration. In complex
figures the concentration is objectified. In _equal_ division subject
has little to do with it; the _unequal_ depends on the subject--it
calls for appreciation. Center of references is the division point,
and the eye movements to right and left begin here, and here return.
The line centers there. The balance is a horizontal affair.

_B_. Center a more reposing division. Chief attention to division
point, with side excursions to right and left, when refreshment of
perception is needed. The balance is horizontal and not vertical.

_C_. A balance with variety, or without symmetry. Centers at division
point and wants sweep over long part. More concentration on short
part. Subjective activity there--an introduction of energy. A
contraction of the muscles used in active attention. Long side easier,
takes care of itself, self-poised. Line centers at division point.
Active with short division. Introduces activity, which is equivalent
to the filling that the complex figures have; in these the introduced
activity is objectified--made graphic.

_D_. Focal point at division point: wants the interesting things in a
picture to occupy the left (when short division is also on left).
Short division the more interesting and means greater complication.
When the pleasing division is made, eyes move first over long and then
over short. Division point the center of real reference from which
movements are made.

_E_. No reference to center in making judgments; hurries over center.
All portions of simple line of equal interest; but in unequal division
the short gets a non-apparent importance, for the line is then a
scheme for the representation of materials of different interest
values. When the division is too short, the imagination refuses to
give it the proportionally greater importance that it would demand.
When too long it is too near equality. In enjoying line, the division
point is fixed, with shifts of attention from side to side. An
underlying intellectual assignment of more value to short side, and
then the sense-pleasure comes; the two sides have then an equality.

_F_. Middle vulgar, common, prosaic; unequal lively. Prefers the
lively. Eyes rest on division point, moving to the end of long and
then of short. Ease, simplicity and restfulness are proper to the long
part of complex figures. Short part of simple line looks wider,
brighter and more important than long.

_G_. Unequal better than equal. Eye likes movement over long and then
over short. Subject interested only in division point. Short part
gives the aesthetic quality to the line.

_H_. Center not wanted. Division point the center of interest. (No
further noteworthy introspection from _H_, but concerning complex
figures he said that he wanted simple or the compact on the short, and
the interesting on the long.)

These introspective notes were given at different times, and any
repetitions serve only to show constancy. The subjects were usually
very certain of their introspection. In general it appears to me to
warrant these three statements: (1) That the center of interest is the
division point, whence eye-movements, or innervations involving,
perhaps, the whole motor system, are made to either side. (2) That
there is some sort of balance or equivalence obtained (a bilateral
symmetry), which is not, however, a vertical balance--that is, one of
weights pulling downwards, according to the principle of the lever.
All the subjects repudiated the suggestion of vertical balance. (3)
That the long side means ease and simplicity, and represents
graphically exactly what it means; that the short side means greater
intensity, concentration, or complexity, and that this is substituted
by the subject; the short division, unlike the long, means something
that it does not graphically represent.

So much for the relation between what is objectively given and the
significance subjectively attributed to it. There remains still the
translation into psychophysical terms. The results on the complex
figures (showing that a division may be shortened by making the
innervations on that side increasingly more involved) lend
plausibility to the interpretation that the additional significance
is, in visual terms, a greater intricacy or difficulty of
eye-movement, actual or reproduced; or, in more general terms, a
greater tension of the entire motor system. In such figures the
psychophysical conditions for our pleasure in the unequal division of
the simple horizontal line are merely graphically symbolized, not
necessarily duplicated. On page 553 I roughly suggested what occurs in
regarding the unequally divided line. More exactly, this: the long
section of the line gives a free sweep of the eyes from the division
point, the center, to the end; or again, a free innervation of the
motor system. The sweep the subject makes sure of. Then, with that as
standard, the aesthetic impulse is to secure an equal and similar
movement, from the center, in the opposite direction. It is checked,
however, by the end point of the short side. The result is the
innervation of antagonistic muscles, by which the impression is
intensified. For any given subject, then, the pleasing unequal
division is at that point which causes quantitatively equal
physiological discharges, consisting of the simple movement, on one
hand, and, on the other, the same kind of movement, compounded with
the additional innervation of the antagonists resulting from the
resistance of the end point. Since, when the characteristic movements
are being made for one side, the other is always in simultaneous
vision, the sweep receives, by contrast, further accentuation, and the
innervation of antagonists doubtless begins as soon as movement on the
short side is begun. The whole of the short movement is, therefore,
really a resultant of the tendency to sweep and this necessary
innervation of antagonists. The correlate of the equivalent
innervations is equal sensations of energy of movement coming from the
two sides. Hence the feeling of balance. Hence (from the lack of
unimpeded movement on the short side) the feeling there of
'intensity,' or 'concentration,' or 'greater significance.' Hence,
too, the 'ease,' the 'simplicity,' the 'placidity' of the long side.

As in traditional symmetry, the element of unity or identity, in
unequal division, is a repetition, in quantitative terms, on one side,
of what is given on the other. In the simple line the _equal_ division
gives us obviously exact objective repetition, so that the
psychophysical correlates are more easily inferred, while the
_unequal_ offers apparently no compensation. But the psychophysical
contribution of energies is not gratuitous. The function of the
increment of length on one side, which in the centrally divided line
makes the divisions equal, is assumed in unequal division by the end
point of the short side; the uniform motor innervations in the former
become, in the latter, the additional innervation of antagonists,
which gives the equality. The two are separated only in degree. The
latter may truly be called, however, a symmetry of a higher order,
because objectively the disposition of its elements is not graphically
obvious, and psychophysically, the quantitative unity is attained
through a greater variety of processes. Thus, in complex works of art,
what at first appears to be an unsymmetrical composition, is, if
beautiful, only a subtle symmetry. There is present, of course, an
arithmetically unequal division of horizontal extent, aside from the
filling. But our pleasure in this, _without_ filling, has been seen to
be also a pleasure in symmetry. We have, then, the symmetry of equally
divided extents and of unequally divided extents. They have in common
bilateral equivalence of psychophysical processes; the nature of these
differs. In both the principle of unity is the same. The variety
through which it works is different.

* * * * *

STUDIES IN ANIMAL PSYCHOLOGY.

* * * * *

HABIT FORMATION IN THE CRAWFISH CAMBARUS AFFINIS.[1]

BY ROBERT M. YERKES AND GURRY E. HUGGINS.

[1] See also Yerkes, Robert: 'Habit-Formation in the Green
Crab, _Carcinus Granulalus_,' _Biological Bulletin_, Vol. III.,
1902, pp. 241-244.

This paper is an account of some experiments made for the purpose of
testing the ability of the crawfish to profit by experience. It is
well known that most vertebrates are able to learn, but of the
invertebrates there are several classes which have not as yet been
tested.

The only experimental study of habit formation in a crustacean which
we have found is that of Albrecht Bethe[2] on the crab, _Carcinus
maenas_. In his excellent paper on the structure of the nervous system
of _Carcinus_ Bethe calls attention to a few experiments which he made
to determine, as he puts it, whether the crab possesses psychic
processes. The following are the observations made by him. Experiment
I. A crab was placed in a basin which contained in its darkest corner
an _Eledone_ (a Cephalopod). The crab at once moved into the dark
region because of its instinct to hide, and was seized by the
_Eledone_ and drawn under its mantle. The experimenter then quickly
freed the crab from its enemy and returned it to the other end of the
basin. But again the crab returned to the dark and was seized. This
was repeated with one animal five times and with another six times
without the least evidence that the crabs profited by their
experiences with the _Eledone_. Experiment 2. Crabs in an aquarium
were baited with meat. The experimenter held his hand above the food
and each time the hungry crab seized it he caught the animal and
maltreated it, thus trying to teach the crabs that meat meant danger.
But as in the previous experiment several repetitions of the
experience failed to teach the crabs that the hand should be avoided.
From these observations Bethe concludes that _Carcinus_ has no
'psychic qualities' (_i.e._, is unable to profit by experience), but
is a reflex machine.

[2] Bethe, Albrecht: 'Das Centralnervensystem von _Carcinus
maenas_,' II. Theil., _Arch. f. mikr. Anat._, Bd. 51, 1898, S.
447.

Bethe's first test is unsatisfactory because the crabs have a strong
tendency to hide from the experimenter in the darkest corner. Hence,
if an association was formed, there would necessarily be a conflict of
impulses, and the region in which the animal would remain would depend
upon the relative strengths of its fear of the experimenter and of the
_Eledone_. This objection is not so weighty, however, as is that which
must obviously be made to the number of observations upon which the
conclusions are based. Five or even twenty-five repetitions of such an
experiment would be an inadequate basis for the statements made by
Bethe. At least a hundred trials should have been made. The same
objection holds in case of the second experiment. In all probability
Bethe's statements were made in the light of long and close
observation of the life habits of _Carcinus_; we do not wish,
therefore, to deny the value of his observations, but before accepting
his conclusions it is our purpose to make a more thorough test of the
ability of crustaceans to learn.

[Illustration: FIG. 1. Ground Plan of Labyrinth. _T_, triangular
compartment from which animal was started; _P_, partition at exit;
_G_, glass plate closing one exit passage. Scale 1/6.]

For determining whether the crawfish is able to learn a simple form of
the labyrinth method was employed. A wooden box (Fig. 1) 35 cm. long,
24 cm. wide and 15 cm. deep, with one end open, and at the other end
a triangular compartment which communicated with the main portion of
the box by an opening 5 cm. wide, served as an experiment box. At the
open end of this box a partition (_P_) 6 cm. long divided the opening
into two passages of equal width. Either of these passages could be
closed with a glass plate (_G_), and the subject thus forced to escape
from the box by the choice of a certain passage. This box, during the
experiments, was placed in the aquarium in which the animals lived. In
order to facilitate the movement of the crawfish toward the water, the
open end was placed on a level with the water in the aquarium, and the
other end was raised so that the box made an angle of 6 deg. with the
horizontal.

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 3 squared 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.

squaredOne 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 deg.. 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.