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

K (50) -33.72 33.72 71.33 +19.49 19.49 55.22

L (20) -39.10 45.90 33.60 -68.65 69.25 25.20

Average: - 9.61 41.20 36.85 -19.94 39.02 28.48

Normal: -64.14 67.08 33.51

The results of rotating the whole body backward through forty-five and

ninety degrees are given in the following table:

TABLE IX.

Observer. Rotation of 45°. Rotation of 90°.

C.E. A.D. M.V. C.E. A.D. M.V.

B (30) + 4.10 24.57 18.56

D (30) +291.03 291.03 61.86

G (50) +266.78 266.78 22.83 +200.16 200.16 11.00

F (60) +116.45 116.45 17.14 - 36.06 36.30 6.29

J (20) +174.30 174.63 30.94

Average: +170.53 174.69 30.66

The errors which appear in these tables are not consistently of the

type presented in the well-known rotation of visual planes

subjectively determined under conditions of abnormal relations of the

head or body in space. When the head is rotated upward on its lateral

horizontal axis the average location of the subjective horizon,

though still depressed below the true objective, is higher than when

rotation takes place in the opposite direction. When the whole body is

rotated backward through 45° a positive displacement of large amount

takes place in the case of all observers. When the rotation extends to

90°, the body now reclining horizontally but with the head supported

in a raised position to allow of free vision, an upward displacement

occurs in the case of one of the two observers, and in that of the

other a displacement in the opposite direction. When change of

position takes place in the head only, the mean variation is decidedly

greater if the rotation be upward than if it be downward, its value in

the former case being above, in the latter below that of the normal.

When the whole body is rotated backward through 45° the mean variation

is but slightly greater than under normal conditions; when the

rotation is through 90° it is much less. A part of this reduction is

probably due to training. In general, it may be said that the

disturbance of the normal body relations affects the location of the

subjective horizon, but the specific nature and extent of this

influence is left obscure by these experiments. The ordinary movements

of eyes and head are largely independent of one another, and even when

closed the movements of the eyes do not always symmetrically follow

those of the head. The variations in the two processes have been

measured by Münsterberg and Campbell[1] in reference to a single

condition, namely, the relation of attention to and interest in the

objects observed to the direction of sight in the closed eyes after

movement of the head. But apart from the influence of such secondary

elements of ideational origin, there is reason to believe that the

mere movement of the head from its normal position on the shoulders up

or down, to one side or the other, is accompanied by compensatory

motion of the eyes in an opposite direction, which tends to keep the

axis of vision nearer to the primary position. When the chin is

elevated or depressed, this negative reflex adjustment is more

pronounced and constant than when the movement is from side to side.

In the majority of cases the retrograde movement of the eyes does not

equal the head movement in extent, especially if the latter be

extreme.

[1] Münsterberg, H., and Campbell, W.W.: PSYCHOLOGICAL REVIEW,

I., 1894, p. 441.

The origin of such compensatory reactions is connected with the

permanent relations of the whole bodily organism to the important

objects which surround it. The relations of the body to the landscape

are fairly fixed. The objects which it is important to watch lie in a

belt which is roughly on a horizontal plane with the observing eye.

They move or are moved about over the surface of the ground and do not

undergo any large vertical displacement. It is of high importance,

therefore, that the eye should be capable of continuous observation of

such objects through facile response to the stimulus of their visual

appearance and movements, in independence of the orientation of the

head. There are no such determinate spatial relations between body

position and the world of important visual objects in the case of

those animals which are immersed in a free medium; and in the

organization of the fish and the bird, therefore, one should not

expect the development of such free sensory reflexes of the eye in

independence of head movements as we know to be characteristic of the

higher land vertebrates. In both of the former types the eye is fixed

in its socket, movements of the whole head or body becoming the

mechanism of adjustment to new objects of observation. In the

adjustment of the human eye the reflex determination through sensory

stimuli is so facile as to counteract all ordinary movements of the

head, the gaze remaining fixed upon the object through a series of

minute and rapidly repeated sensory reflexes. When the eyes are closed

and no such visual stimuli are presented, similar reflexes take place

in response to the movements of the head, mediated possibly by

sensations connected with changes in position of the planes of the

semicircular canals.

VII.

If eye-strain be a significant element in the process of determining

the subjective horizon, the induction of a new center of muscular

equilibrium by training the eyes to become accustomed to unusual

positions should result in the appearance of characteristic errors of

displacement. In the case of two observers, A and H, the eyes were

sharply raised or lowered for eight seconds before giving judgment as

to the position of the illuminated spot, which was exposed at the

moment when the eyes were brought back to the primary position. The

effect of any such vertical rotation is to stretch the antagonistic

set of muscles. It follows that when the eye is rotated in the

contrary direction the condition of equilibrium appears sooner than in

normal vision. In the case of both observers the subjective horizon

was located higher when judgment was made after keeping the eyes

raised, and lower when the line of sight had been depressed. In the

case of only one observer was a quantitative estimation of the error

made, as follows: With preliminary raising of the eyes the location

was +36’.4; with preliminary lowering, -11’.4.

When the illuminated button is exposed in a darkened room and is

fixated by the observer, it undergoes a variety of changes in apparent

position due to unconscious shifting of the point of regard, the

change in local relations of the retinal stimulation being erroneously

attributed to movements in the object. These movements were not of

frequent enough occurrence to form the basis of conclusions as to the

position at which the eyes tended to come to a state of rest. The

number reported was forty-two, and the movement observed was rather a

wandering than an approximation toward a definite position of

equilibrium. The spot very rarely presented the appearance of sidewise

floating, but this may have been the result of a preconception on the

part of the observer rather than an indication of a lessened liability

to movements in a horizontal plane. Objective movements in the latter

direction the observer knew to be impossible, while vertical

displacements were expected. Any violent movement of the head or eyes

dispelled the impression of floating at once. The phenomenon appeared

only when the illuminated spot had been fixated for an appreciable

period of time. Its occurrence appears to be due to a fatigue process

in consequence of which the mechanism becomes insensible to slight

changes resulting from releases among the tensions upon which constant

fixation depends. When the insensitiveness of fatigue is avoided by a

slow continuous change in the position of the illuminated spot, no

such wandering of the eye from its original point of regard occurs,

and the spot does not float. The rate at which such objective

movements may take place without awareness on the part of the observer

is surprisingly great. Here the fatigue due to sustained fixation is

obviated by the series of rapid and slight sensory reflexes which take

place; these have the effect of keeping unchanged the retinal

relations of the image cast by the illuminated spot, and being

undiscriminated in the consciousness of the observer the position of

the point of regard is apprehended by him as stationary. The

biological importance of such facile and unconscious adjustment of the

mechanism of vision to the moving object needs no emphasis; but the

relation of these obscure movements of the eyes to the process of

determining the plane of the subjective horizon should be pointed out.

The sense of horizontality in the axes of vision is a transient

experience, inner conviction being at its highest in the first moments

of perception and declining so characteristically from this maximum

that in almost every case the individual judgment long dwelt upon is

unsatisfactory to the observer. This change I conceive to be a

secondary phenomenon due to the appearance of the visual wanderings

already described.

VIII.

The influence of sensory reflexes in the eye upon the process of

visual orientation was next taken up in connection with two specific

types of stimulation. At top and bottom of the vertical screen were

arranged dark lanterns consisting of electric bulbs enclosed in

blackened boxes, the fronts of which were covered with a series of

sheets of white tissue-paper, by which the light was decentralized and

reduced in intensity, and of blue glass, by which the yellow quality

of the light was neutralized. Either of these lanterns could be

illuminated at will by the pressure of a button. All other

experimental conditions remained unchanged. The observers were

directed to pay no special regard to these lights, and the reports

show that in almost every case they had no conscious relation to the

judgment. The results are presented in the following table:

TABLE X.

Light Below. Light Above.

Observer. Const.Err. Av.Dev. M.Var. Const.Err. Av.Dev. M.Var.

C (40) +156.37 156.37 19.67 +169.85 169.85 19.22

D (20) + 39.30 43.30 17.95 + 46.65 47.35 15.41

F (30) + 19.47 19.47 8.83 + 58.37 58.37 7.83

G (50) + 66.11 112.76 14.65 +117.86 117.86 13.10

H (30) -147.63 147.63 21.07 -105.30 105.30 30.31

J (20) + 1.90 31.95 22.33 + 44.40 44.40 20.55

Average: + 22.59 85.28 17.42 + 55.30 90.52 17.74

The eye is uniformly attracted toward the light and the location of

the disk correspondingly elevated or depressed. The amount of

displacement which appears is relatively large. It will be found to

vary with the intensity, extent and distance of the illuminated

surfaces introduced. There can be little doubt that the practical

judgments of life are likewise affected by the distribution of light

intensities, and possibly also of significant objects, above and below

the horizon belt. Every brilliant object attracts the eye toward

itself; and the horizon beneath a low sun or moon will be found to be

located higher than in a clouded sky. The upper half of the ordinary

field of view—the clear sky—is undiversified and unimportant; the

lower half is full of objects and has significance. We should probably

be right in attributing to these characteristic differences a share in

the production of the negative error of judgment which appears in

judgments made in daylight. The introduction of such supplementary

stimuli appears to have little effect upon the regularity of the

series of judgments, the values of the mean variations being

relatively low: 17’.42 with light below, 17’.74 with it above.

IX.

In the final series of experiments the influence of limiting visual

planes upon the determination of the subjective horizon was taken up.

It had been noticed by Dr. Münsterberg in the course of travel in hill

country that