INTRODUCTION
To the Student:
PsYCHOLOGY is a systematic study of mental lîfe. You now turn from the study of physical forces, rocks, flowers, and animal tissues, in nature without, to a study of your own mind. You are to perform expérimenta upon yourself .
The expérimental method enables you to analyze and reduce a mental process to its simplest éléments; to control, repeat, and vary the conditions systematically ; to record the results; to trace interrelations and explanations of known phenomena; and to discover new f acts and problems.
This manual is so arranged as to furnish set exercises in which directions, aids, and explanations are given in the order needed. Only a few of the most gênerai suggestions for your guidance need be given hère.
Finish as you go along. The paragraph is the unit ; always read a paragraph at a time and perform the experiment, write the report, or master the explanation before you read the next. This is mandatory, because glancing ahead would of ten vitiate the experiment.
Take systematic notes. The directions for notes are spécifie in certain minimum requirements. Thèse notes are not primarily for the information of the instructor, or for reviews and examinations, but for the purpose
X INixlODUCTION
of clinching the observed facts and gaining practice in the recording of the results, which is an essential step in an experiment. Use loose-leaf note-books ; hand in the report for each expçriment to the instructor for inspection ; and file the notes as they are returned.
Work intensively. Seek the most thorough insight into the problem under considération ; note new observations, test ideas suggested to you, verify and check as much as tinae permits. Eeason, and thus develop confidence in your own judgment and power of observation. But always adhère to the set topic. Do not ramble, or foUow up the countless fascinating side lines which corne to view. FoUow the directions closely, then develop your original ideas.
Apply what you learn. You will learn, for example, many laws of mental economy in this course. When you hâve discovered and demonstrated such laws, use them. Economize mental energy! Psychologize in your history lesson, your literature, your material science, your athletics, — wherever you are concerned with mental processes. To educate, to heal, to govern, to please, to interpret the efforts and products of the human mind; to understand inclinations, proclivities, and capacities of your own and other minds, involves knowledge of mind, which is psychology.*
* "Only with the aid of psychology can one to the fullest possible extent reap the benefits of the study of other forms of science. Language cannot be imderstood, literature cannot be appreciated, read, and interpreted, art cannot be profoundly comprehended, and even the natural sciences cannot hâve their full import revealed, without a knowledge of the mind of man. And, indeed, how could this be otherwise, since ail science itself is only the product of the human mind?" (Ladd.)
INTKODUCTION xî
Be impartial: be not self-centered. You will be called upon to exhibit and measure jour mental capacities in varions ways, and it requires the integrity and courage of a scientist to observe and report thèse without bias.
Go only as far in an assignment as you can go thoroughly. One student may be able to proceed two or three times as fast as another. If you find that the lesson is too long for you, do not skim over any part, but proceed as far as you can and record the time limit.
In the experiments that follow, *Tor one" means that the experiments so headed may be performed by one person alone. "For two'' means that two mùst work together, one acting as expérimenter (E) and the other as observer (O). Shift in each experiment so that each one may serve in turn both as expérimenter and as observer. Eecord which one served as observer first. Each should keep the notes which naturally go into his book according to the directions. Eecord also the date, the hour of the beginning of the experiment, interruptions, and any gênerai conditions which might influence the results. Use terse language.
To experiment is to ask questions of nature. Do not simply repeat the set questions of the book, but let them open deeper and more serviceable inquiries into your mental nature. Your primary aim in this course should be, not to collect facts, but to acquire training. Carry habits of introspection, précision, analysis, and natural explanation into life and you will realize the force of our motto : Not psychology, but to psychologize.
CHAPTEE I
VISUAL AFTER-IMAGES
For One,*
MosT of US hâve observed that, if we look for a moment at a light as it is being turned out, we see an image of it a while afterward. That image is an af terimage, or after-sensation. Such images manifest themselves according to traceable laws and play an important, though seldom recognized, rôle in our expérience. We shall now make a study of some of their characteristic modes of behavior.
Suceess in this experiment dépends mainly npon concentration of attention and economy in the use of the eyes. The eyes should not be allowed to wander aimlessly over the figures, and it is well to close them for rest as often as possible. Clear images can be obtained only after steady fixation. It is easier to get the after-image with one eye alone, but in the long run it is more restful to use the two eyes together.
1. Existence, a. Brightness. — Place the black square at the center of the upper half of a white sheet of paper; fixate the center of it (i.e., look intently and
*Take from the envelope the large black and gray squares, and the following small squares: black, gray, white, red, blue, yellow, green, violet, and orange. Make a pinhole at the center of each of thèse squares.
2 VISUAL AFTEE-IMA-
steadily at the pinhole) for about fiftt i
look at the center of the lower half of i
paper and you will see a bright squ after-image. Kecord your estimate o and duration.
b. Color. — Try the red square in tj Record the color of the after-image.
An after-image is a sensory image i
the resuit of the stimulation of a i
not until after the stimulus has been is a sort of écho and bears certain rela ject of which it is a copy as regards spj i the primary impression, sensé quality, Thus, in this experiment, you saw, on the blank paper, copies of the squares p( original in every respect except brightne After-images combine certain characterii tiens and mental images and might eq called after-sensations.
The causes of after-images are preseï vision and tend to modify practically ail Yet many persons live long and happily wi i allowance for their distortions or even di.' : existence of them. Every object that we i iiïipression which may bob up as an after-i] ficiently strong and isolated. We look at black paper and the next moment we , i
*A fixation- tîme of fifteen seconds is too long too short for other observers; each wiU soon deli time is most favorable for his eyes.
f Black, white, and ail the intervening grays are t nesses. Brightness is also présent in color.
VISUAL AFTER-IMAGES 3
of it wherever we cast our eyes ; the same is true about a light, a color, an apple, a man, ac tree, a book, a house — any object which may impress the eye. The af terimages in themselves are not useful, and itis fortunate that we hâve the instinctive power to disregard them as effectively as we do. But even though we disregard them, they modify our sensory expérience and con,tinually tone the colors, lights, and shades of our environment.
After-images occur in ail the sensés, but the visual are the most conspicuous.
2. Setting. — Kepeat Exp. 1 a and observe that, when the light after-image appears, there is a change in the white surface surrounding it.* Describe the change.
When we look at an object we may secure an afterimage not only of that object but also of its surroundings within a limited field of vision. This complexity of the impression is one of the reasons why spécifie after-images are so difficult to detect and so easy to disregard.
After-images are local effects of the adaptation of the eye to changes in brightness and color. When we enter a dark room, it seems at first intensely dark, but later it assumes gray or color effects. When we pass from a dark into a light room, the light at first is dazzling, but the eye soon adapts itself so that after a while the light does not seem so bright. During adaptation ail brightnesses and ail colors tend toward
* If the white sheet is plaoed against a. dark background, the outline of the whole sheet may be seen in the after-image.
4 VISUAL L
grsij. In the above exper retina is adapted to dark to light.
3. Color. — In successive i of the five colors, blue, green, Eecord the dominating color i you formulate a law for this state it.
The after-image of any colo of rapid changes, possibly coveri but there is always one partiel inates by being the most distinct longest. This color is complément, stimulus.t Of course it is modifi tain laws, by the color and the bri^ ground upon which it is projected.
The after-image of the dark sti experiment was light; that is, antag therefore combine the observations o on color and say that the dominant cok >
of an after-image are antagonistic te ;
brightness of the stimulus. AU color a. i
involve brightness-effects. Colors are of (
after-images of non-colored objects.
4. Projectîon-background. a, Brightr. i Brightness. — Eepeat Exp. 1 a in six suce i
* Do not try thèse în too rapid succession ; it ir. intersperse them with following experiments. Be\ ing at the colors out of mère curiosity or aimlessne !
f Every color has a complementary, i.e., an opposi ; onistic color. Colors are said to be complément i neutralize each other and produce gray when mixed.
VISUAL AFTER-IMAGES 6
under uniform conditions, except that you project the image upon différent baekgrounds ; * namely, white, gray, and black, in the double-fatigue order.f Kecord the relative effectiveness of the three baekgrounds.
The clearness of an image dépends upon the brightness-difference between it and its projection-baekground. When projected upon the white ground, in this experiment, the light of the image is intensified and the darkness of the surroundings is reduced by the white; on the black ground, the light of the image is minimized and the darkness of the surroundings is enhanced by the black; while, on the gray, there is a moderate interférence with both image and surroundings. Hence brightness of the background makes comparatively little différence in the effectiveness of the after-image, although the brightness of the three images varies greatly. For a dark object the white projectionbackground is, however, usually more effective, because hère the white enhances the image of the object itself, whereas on a black projection-background it is the background of the object that is enhanced.
b. Brightness-effect on Color, — Repeat Exp. 1 6 in three successive trials, projecting the image upon white, gray, and black baekgrounds respectively. Record the effect of the background upon the color of the afterimage.
*Use the two large squares for gray and black projectîon-backgrounds.
•\ Double-fatigue order is the technical term for the giving of a séries of trials in one order and repeating them in the reverse order; thus, white, gray, black; black, gray, white. The theory is that such factors as fatigue and practice tend to even up by this order.
6 VISUAL AFTER-I]L JES
There is a distinct effect upon the brightness of the color; the actual color of the image mixes with the brightness of the background.
c. Color-effect on Color. — Project the after-image of the red square, in successive trials, upon the yellow, the blue, and the red square itself. Record the resulting color-effects.
The color of the after-image mixes with the color of the background. Thus, the resuit on the yellow is a greenish yellow; on the blue, a greenish blue; and on the red a tendency toward gray. This last trial — red upon red — explains why colors change and blur when we look intently at them; the after-image of the red disk is a pale green, and if it were projected upon a pale red of the same strength, the resuit would be to cancel both colors, according to the law of complementaries.
d. Absence of Background, — Fixate the black square as before, and then put your hands over your eyes and you will see the image projected somewhere into space.* Record your estimate of its size and distance and the relative effectiveness of this and the foregoing modes of projection.
The image may be projected anywhere — upon any color or brightness, upon any form, at any distance within sight. A glance at the setting sun produces shifting color-effects upon the object we look at immediately afterward ; the after-image of the green leaf in
* It is usuaUy better to keep the eyes open when covered by the hands; still, it makes but little différence whether they are open or closed, provided the covering is adéquate.
VISUAL AFTER-IMAGES 7
a woman's hat may be taken for a rosy blush upon her cheek.
5. Négative and Positive — Look at a lighted lamp * for half a second, and then instantly cover the eyes and observe the radical changes in color of the after-image. Record the two dominant colors in the order of their appearance.t
The positive after-image has the same relations of brightness as the stimulus, as in a photographie positive. The négative after-image has the relations of light and shade reversed, as in the photographie négative. The after-image may be of the same color as the stimulus, or it may be other-colored. There are positive same-colored and positive other-colored, négative same-colored and négative other-colored afterimages. Generally, however, positive after-images are same-colored and négative other-colored are complementary.
The positive after-image appears first and is usually very short in duration and difficult to detect. To make it conspicuous, one must employ a strong stimulus, as in this experiment. After some training one may see the positive after-image before the négative in the exposure of ordinary objects of moderato intensity.
*Any kînd: daylight does not interfère seriously.
f Positive after-images of brightness without color may be demonstrated as follows: Face some distant object, as the branching limb of a tree outlined against a clear sky; close the eyes and cover with the hands for a minute; then open the hands and eyes for a fraction of a second, and observe, immediately after elosing the eyes again, an image like the object in brightness. This is the positive after-image.
8 VISUAL AFTER-IMj9
6. Size and Distance. — In three project an af ter-image of the black squ upon backgrounds at différent distanc e.g., 1 ft., 3 ft., and 10 ft. Formul relation between size and distance.
This variation of the size with dist the after-image foUows the same optic projection as the normal retinal image i
7. Relief. — Project an after-image of globe, or any other object that présents re Is there any suggestion of relief or volum image?
The perception of relief dépends upon t. between the images in the two eyes, delica in brightness, and eye-movements, among The blurred edges, the reversai of brightn confusion of eye-muscle sensations militate perceptions of relief in the after-image. the after-image présents only the outline an suggest relief, but training and care may < to identify marks of relief.
8. Plasticity. — Project an after-image of square, into an* upper corner of the room. whether the image adapts itself to the ceiling i surfaces, or retains its flat f orm.
It may do either; which it shall do is a m apperception. Usually it adapts itself plasticall; surfaces. This is partiçularly true if the image jected upon some familiar surface, as the sleeve hand.
VISUAL AFTER-IMAGES 9
9. Movement. — Fixate the black square, as in Exp. 1 a, and project the image with eyes closed and covered by the hands, and try to keep the after-image directly before you. Does the image seem to move irresistibly ? If so, in what direction ?
It is clear by this time that the after-image moves with the eyes ; with the eyes open, we see it in whatever direction we look. But when the eyes are closed, and we are not aware of their movement, most observers find that the image h as a curiously irrésistible tendency to move upward.
