Harvard Psychological Studies Part 69

Secondly, four of the subjects only (_E_, _F_, _G_ and _H_) had judgments also on the side which gave the complex filling the larger s.p.a.ce; to _E_, _F_ and _G_, these were secondary preferences; to _H_ they were always primary. Thirdly, the judgments on No. III. are less, in spite of the fact that the larger component parts of No. II., might be taken as additional weight to that side of the line, and given, therefore, the shorter s.p.a.ce, according to the principle of the lever.

The subjects, then, that appear not to substantiate our suggested theory are _E_ and _H_, who in the reversed figures give the shorter s.p.a.ce to the less complex filling, and _F_ and _G_, who, together with _E_ and _H_, have always secondary judgments that allot to either complex filling a larger s.p.a.ce than to the simple horizontal.

Consider, first, subjects _E_ and _H_. For each, the difference in division of II. and III. is in any case very slight. Further, subject _E_, in judgments where the complex filling _exceeds_ the horizontal parallels in length, still gives the more complex of the two fillings markedly the shorter s.p.a.ce, showing, apparently, that its additional complexity works there in accord with the theory. There was, according to his introspection, another principle at work. As a figure, he emphatically preferred II. to III. The filling of II. made up, he found, by its greater interest, for lack of length. He here secured a balance, in which the interest of the complex material compensated for the greater _extent_ of the simpler horizontals. This accounts for its small variation from III., and even for its occupying the smaller s.p.a.ce. But in judgments giving the two complex fillings the larger s.p.a.ce, the more interesting material _exceeded_ in extent the less interesting. In such divisions the balance was no longer uppermost in mind, but the desire to get as much as possible of the interesting filling. To this end the horizontal parallels were shortened as far as they could be without becoming insignificant. But unless some element of balance were there (although not present to introspection) each complex filling, when up for judgment, would have been pushed to the same limit. It, therefore, does seem, in cases where the complex fillings occupied a larger s.p.a.ce than the horizontals, that the subject, not trying consciously to secure a balance of _interests_, was influenced more purely by the factor of complexity, and that his judgments lend support to our theory.

Subject H was the only subject who consistently _preferred_ to have all complex fillings occupy the larger s.p.a.ce. Introspection invariably revealed the same principle of procedure--he strove to get as much of the interesting material as he could. He thought, therefore, that in every case he moved the complex filling to that limit of the pleasing range that he found on the simple line, which would yield him most of the filling. Balance did not appear prominent in his introspection. A glance, however, at the results shows that his introspection is contradicted. For he maintains approximately the same division on the right in all the figures, whether reversed or not, and similarly on the left. The average on the right for all four is 67; on the left it is 74. Comparing these with the averages on the simple line, we see that the right averages coincide exactly, while the left but slightly differ. I suspect, indeed, that the fillings did not mean much to _H_, except that they were 'interesting' or 'uninteresting'; that aside from this he was really abstracting from the filling and making the same judgments that he would make on the simple line. Since he was continually aware that they fell within the 'pleasing range' on the simple line, this conclusion is the more plausible.

Perhaps these remarks account for the respective uniformities of the judgments of _E_ and _H_, and their departure from the tendency of the other subjects to give the more complex filling constantly the shorter s.p.a.ce. But subjects _F_ and _G_ also had judgments (secondary with both of them) giving to the complex filling a larger extent than to the parallels. With them one of two principles, I think, applies: The judgments are either instances of abstraction from the filling, as with _H_, or one of simpler gravity or vertical balance, as distinguished from the horizontal equivalence which I conceive to be at the basis of the other divisions. With _F_ it is likely to be the latter, since the divisions of the figures under discussion do not approach very closely those of the simple line, and because introspectively he found that the divisions giving the complex the larger s.p.a.ce were 'balance' divisions, while the others were determined with 'reference to the character of the fillings.' From _G_ I had no introspection, and the approximation of his judgments to those he gave for the simple line make it probable that with him the changes in the character of the filling had little significance. The average of his judgments in which the complex filling held the greater s.p.a.ce is 66, while the averages on the simple line were 65 on the left, and 64 on the right. And, in general, abstraction from filling was easy, and to be guarded against. Subject _C_, in the course of the work, confessed to it, quite unsolicited, and corrected himself by giving thenceforth _all_ complex fillings much smaller s.p.a.ce than before. Two others noticed that it was particularly hard not to abstract. Further, none of the four subjects mentioned (with that possible exception of _E_) showed a sensitiveness similar to that of the other five.

With the exception of _H_, and in accord with the constant practice of the other five, these subjects, too, occasionally found no pleasing division in which the complex filling preponderated in length over the horizontals. It was uniformly true, furthermore, in every variation introduced in the course of the investigation, involving a complex and a simple filling, that all the nine subjects but _H_ _preferred_ the complex in the shorter s.p.a.ce; that five refused any divisions offering it in the larger s.p.a.ce; that these five showed more sensitiveness to differences in the character of fillings; and that with one exception (_C_) the divisions of the simple line which these subjects gave were nearer the ends than those of the others. It surely seems plausible that those most endowed with aesthetic sensitiveness would find a division near the center more unequal than one nearer the end; for one side only slightly shorter than the other would at once seem to mean the same thing to them, and yet, because of the obvious difference in length, be something markedly different, and they would therefore demand a part short enough to give them sharp qualitative difference, with, however, in some way, quant.i.tative equivalence. When the short part is too long, it is overcharged with significance, it strives to be two things at once and yet neither in its fulness.

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 subst.i.tution. 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 a.s.signment 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 repet.i.tions 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 subst.i.tuted 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 quant.i.tatively 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 ident.i.ty, in unequal division, is a repet.i.tion, in quant.i.tative terms, on one side, of what is given on the other. In the simple line the _equal_ division gives us obviously exact objective repet.i.tion, 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 a.s.sumed 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 quant.i.tative 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.

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STUDIES IN ANIMAL PSYCHOLOGY.

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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 cla.s.ses 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 repet.i.tions 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 a.s.sociation 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 repet.i.tions 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.

[Ill.u.s.tration: FIG. 1. Ground Plan of Labyrinth. _T_, triangular compartment from which animal was started; _P_, part.i.tion at exit; _G_, gla.s.s plate closing one exit pa.s.sage. 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 part.i.tion (_P_) 6 cm. long divided the opening into two pa.s.sages of equal width. Either of these pa.s.sages could be closed with a gla.s.s plate (_G_), and the subject thus forced to escape from the box by the choice of a certain pa.s.sage. 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 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 s.p.a.ce 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 pa.s.sages was closed. That the animal should not be disturbed during the experiment the observer stood motionless immediately behind the box.

Before the gla.s.s 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 Pa.s.sage Left Pa.s.sage.

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 pa.s.sage, it was closed with the gla.s.s plate, and a series of experiments made to determine whether the crawfish would learn to avoid the blocked pa.s.sage 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 pa.s.sages at the exit. Whenever an animal moved beyond the level of the part.i.tion (_P_) on the side of the closed pa.s.sage the trial was counted in favor of the closed pa.s.sage, even though the animal turned back before touching the gla.s.s plate and escaped by the open pa.s.sage.

TABLE I.

HABIT FORMATION IN THE CRAWFISH.

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 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.