Notes in psychology on lectures supplementary to James' Psychology

Prefatory Note

The presentation to large classes in a limited period of a survey of topics in Psychology most important for introductory study requires all the pedagogical aids that can be made available. The instructor must select his material, bringing to the teaching an individual emphasis, and inevitably supplementing the text in the process. The generous use of demonstrations and charts and diagrams within the lecture hour makes large draughts upon the student's attention and interferes with his notes. The present notes are the result of these conditions. The problems of Sense- Perception are considered the standard ones for the beginning student; a comprehension of principles is regarded as fundamental. It seems better to carry a few problems to a fair degree of completeness than to attempt too broad a survey. Moreover, as these notes are supplementary to James' Psychology, they must be considered along with the text, to restore the proper perspective. Points satisfactorily covered by the text receive no comment or restatement. It has been found impracticable to include in lectures (twice a week for one semester) much of the material of the latter half of the text. The notes will be used by the author in an introductory manual in preparation, the copyright of which is held by Henry Holt & Co.

CHAPTER I. Introductory

Topic I. The Nature of Psychology. Psychology, as the science of mental functions, studies the processes that bring the individual into relation with his environment. Environment embraces the physical world, which contains various forms of energy, and the several biological factors which form the conditions of life.

A special relation obtains between the mind and the body. The nervous system represents the physiological basis of mental functions. The principle that physiological states condition mental states is illustrated by the effect of bodily injuries, and by the action of drugs, both of which show very decided changes of mental state, such as unconsciousness, lack of motor control, emotional exhilaration or depression, hallucinations, impairment of memory, etc. The same principle of relation between mental states and fluctuations in the condition of the nervous system is shown in detail in the minuter changes of condition. These are illustrated by the effects of fatigue, of hunger, of difference between morning and evening, of influences of the weather, of digestion, and of a score of the more delicate variations which make it safe to assume that to every mental state there corresponds some kind of a physiological state of the nervous system.

CHAPTER II. Sensb-Pkrception

Topic II. General Characteristics of Sensation.

Sensation represents the simplest mental process that participates in the mental life. Sensations are thus the first things in consciousness. It is possible to distinguish the bare effect on the organism of being exposed to a stimulus, and to call this the sense-impression. The stimulus is some form of energy in the outer world ; and the sense-organ represents the adaptation of a cell to receive this form of energy. Accordingly the sum total of our sensations is limited by the variety of forms of energy which we have senses to receive. All such adaptations are special, and again are limited in range. Thus: the cells of ^.he retina respond to light-vibrations, and the cells of the end-organ in the ear respond to air-vibrations. Having these specialized responsive organs, we see colors and hear sounds. But the range of color which Ave see is limited by the structure of these cells. AYe know that there are vibrations below the red and beyond the violet which are just the same kind of vibrations, but which we do not see. Similarly we can see, but not hear as sound, the vibrations of a stick which is not vibrating rapidly enough to produce an audible tone ; and we can show that when vibrations get more rapid than the upper limit of hearing, there is a rush of air, but no musical tone. Once more, we know that there are forms of physical energy, like magnetism, for which we have no sense-organs whatever ; we cannot feel the presence of a magnetic field. It may be assumed that the kind and range of our senses represents the maximum utility of sensory functions.

Topic III. Body-informing and World-informing Use of the Senses. The sensations give information regarding conditions of the body for use and protection, particularly as pain and pleasure ; and this factor remains even when it becomes secondary. The chief development of the senses is towards giving information of the outside world; and this use may be called intellectual. It results in the making of distinctions. The 1 accuracy of the sense, or its delicacy, is measured by the smallness of the distinctions which it makes. These distinctions are both in matters of degree and of kind, or quality. What we really distinguish are qualities of objects, but the information may be reduced by psychology to types of qualities, such as color and form, and again size and distance for vision; or loud and low, high and deep tones for hearing; heavy and light, hot and cold, for touch ; sour and sweet for taste ; and so on. In all these distinctions the factor of use, or pain and pleasure as protective, remains, but in many cases is slight, giving way to distinction.

Topic IV. Sensation and Action. The use of distinctions is to regulate conduct. Situations must be distinguished so that they may be appropriately reacted to. In considering distinctions, it is important to think of the situations as simply as possible, and as they commonly occur in nature. Distinctions are directed to. objects. There is a strong tendency to refer all sensations outward and in terms of meaning, to perceive objects and disregard sense-impressions. As a consequence, for the higher senses we are very little aware of sense-impressions, and at once infer the presence and nature of the objects which cause them. Hence, we often fail to realize the basis in sensation of the result which we perceive or infer. For example, we know that we distinguish the direction of sounds, but need experiment to prove that the basis of this distinction is a difference in intensity in the two ears. Again, we are very likely to infer that a light that is growing brighter is nearer. We are not usually aware that brightness is the basis of our inference of nearness. "What we seem to perceive are objects or situations in accordance with their most familiar appearance ; the basis of such perception are simple sensible qualities. Out of these sensations we at once build up objects. We seem to perceive them as a whole, and overlook the steps involved.

Topic V. Intensity. Among the qualities in common to all sensation is that of intensity, which is the simple distinction of more or less. Intensity has the advantage of being easily studied. Changes in degree, such as that of a weight growing heavier, of a light growing brighter, of a sound growing louder, are relatively simple distinctions. It is true that the sensation may change slightly in quality as the weight grows heavier or the sound louder or the light brighter; but we can distinguish the predominant element of change of degree, and can usually distinguish this from a qualitative change, such as that the tone becomes higher, or the light more bluish, or the pressure duller or sharper. Changes in intensity have been minutely studied. One of the important results is that relative! differences are shown to be more important than absolute ones. This is again in accord with natural use, and indicates that there is a standard of utility in making distinctions. It may be illustrated in terms of weight by saying that one ounce added to four or five ounces will be much more marked than one ounce added to twenty or twenty-five ounces. When this principle is made accurate, it would read that a change of one ounce in a pound would be about as perceptible as a change of two ounces in two pounds. Just how far the law holds will be seen later. The principle is clear that the perceptibility of the difference stands in very definite relation to the total impression. It is also true that sudden changes are more perceptible than gradual ones. We do not observe that a room is growing warmer as we sit in it, but someone coming from outdoors notices that it is too hot. Another general factor is contrast, which means; that the present condition of the organ affects the impression, and also that one impression affects another. Such contrast is an illustration of the fact that a sensation is relative, and its effect depends upon the total impression. Thus, if one hand be placed in hot water and the other in cold, and both transferred to the same dish of lukewarm water, it will seem cold to the hand that has been in hot water, and warm to the one that has been in cold water. Similarly, colors will have a very different effect when placed upon background or another. There are, however, many varieties of contrast to be noticed later.

(It should be noted that the general subject of this chapter is a survey of the qualities which many or all sensations have in common, and of the general processes involved in sensation.)

CHAPTER III. Vision

Topic VI. The Organ of Vision. The study of vision is best adapted to illustrate the principles of sense-perceptions. It makes it possible to trace step by step all the processes from the physical stimulus to the most complex sense-perceptions. "We must consider that the organ of vision, which is the eye, is primarily an organ for color-perception, and again an organ for the perception of form. These two orders of perception are concentrated in the retina, and specifically in a single layer of the retina known as the rod-and-cane layers. These form the end-organs of vision, and are probably at once the end-organs for color and for form. It will be altogether best to describe the structure and functions of the eye in terms of form-perception.

Topic VII. The Formation of the Image: (a) Structure of the Eye. All vision depends upon the formation of an image on the retina. Our first inquiry is as to the structure of the eye, particularly with reference to the parts that lead to the formation of the image, and the method by which each part contributes to the result.

The eye is a sphere a little deeper than broad, and flattened in front, and is about seven-eighths of an inch in diameter. It consists of three coats : the outer or sclerotic, which in front becomes vaulted and transparent, forming the cornea; the middle coat, called the choroid in back, which in front becomes flattened as the iris, with the opening in it, the pupil. Inside is the third coat, the retina alone, which stops at the margin of the ring formed by the junction at once of the retina, the choroid-and-iris, and the sclerotic-andcornea. In addition the solid or liquid contents of the eye appear first in the vitreous humor, quite the' largest in mass, filling all the space between the retina and the iris, except that there is a depression in its anterior surface in which rests the second important solid body, the lens. The space, flat in back and vaulted in front, between the iris and the choroid, is filled with a watery substance and is called the aqueous humor. In addition there are within the eye various blood-vessels, particularly in the choroid, bringing its rich blood-supply, the ligaments which hold the lens in place and which are attached to the two important ciliary muscles through the action of which the lens contracts. The eyeball as a whole is harnessed by a set of six muscles, four of which are straight, one above, one below, one external, and one internal, and two of which are oblique.

In terms of function the sclerotic coat serves as the solid wall keeping the eye in shape, and also as the points of attachment for the muscles. The cornea is of a similar structure as the sclerotic, but transparent to permit the passage of light. The lens has the important function of breaking or refracting the line of light so that the imagine falls on the retina, and not in front or in back of it, and that as well for! near, for middle, or for far distances— this process being known as accommodation. The iris contains the mechanism of light adjustment, the pupil becoming very small in strong light and expanding in weaker light. Considered generally, the eye may be regarded as the retina, which in turn is the expansion of the optic nerve, and a set of accessory mechanisms for regulating the light and forming the image, of which the chief are the lens and the iris.

Topic VIII. The Formation of the Image, (b) Processes and Conditions. While we see with nearly the entire extent of the retina, a fundamentally important condition of accurate vision is that the image shall fall on the fovea. Human vision is peculiarly foveal vision, which means that directly in the center of the retina there is a depression, or fovea, in which vision is concentrated. A ray of light entering horizontally through the exact center of the pupil, would reach the center of the fovea. The structure of the retina shows that the visual elements, or rods and cones, are most closely concentrated at this point, in extent, a space of about one-eighth of an inch. Furthermore, at this point there are cones alone, and these closely crowded. Towards the margins of the fovea there is about one cone to a circle of rods surrounding it; and in the areas farther away from the fovea in all directions the proportions of cones to rods diminish, and both elements are more and more separated by other tissue. This distribution proves that the rod-and-cone layer is the layer of visual perception, and that the cone is more intimately connected with the visual process than the rod. (For structure of retinal layers, see text.) A complementary proof is furnished by the existence of the blind spot, which is the entrance of the optic nerve. At this point, a little to the inside of the fovea, the fibres of this nerve pierce through all the coats of the eye. The retina may be pictured as the spread-out ends of these fibres. Naturally, at this point there are no rods and cones, and hence no vision. (For experiment proving the blind spot, see text.)

Topic IX. General Conditions of Vision. The conditions under which the eyes are used may be divided into "vision with the eye at rest" and "vision with the eye in motion ; ' ' again into ' • vision with one eye ' ' (monocular) and "vision with two eyes" (binocular). For purposes of exposition it is well to accept as the standard "vision with one eye at rest." This affords the simplest conditions. As a matter of experience, the use of the two eyes jointly and in constant motion is the dominant method. The largest share of information, as well as the normal use of the eyes, involves binocular vision and constantly moving vision. Conformably to the general discussion, we may call "vision with the eyes at rest," passive and "with the eyes in motion" active. It will be recalled that we have but two types of sensation: (1) the stimulation of a specialized sense-organ, or (2) the feeling accompanying the contraction of muscle. The sensibility of the retina represents the former type ; the contraction of the muscles in moving the eye, the latter. Active vision combines the two, and refers to the total sum of information which we get from the retinal images, as well as from the feeling of ocular movement.

Remembering the practical and theoretical importance of these four modes of using the eye or eyes, we ask the typical question for each sense, namely, "What are the kinds of information which the sense affords, and how do we get them?" Such analysis must be complete, must yield simple and distinctive types of information. For vision the analysis yields the following result : *

A. The Light-and-Color Sense. B. Space-Perception. These two are doubtless related to quite different phases of the visual process. The colors and the shapes of objects are seen combined; but the color factor and the space factor are readily separated mentally. We distinguish Light and Color, and subdivide the qualities of space-perception as follows :

I. Direction.

II. Form. A. Light.

III. Size. also

IV. Distance. B. Color.

V. Solidity.

YI. Movement.

What this analysis means is that the visual difference between one object and another may be reduced to differences, first, of color (as blue or red), and brightness (as light or dark) ; and secondly, to differences in space relations, of directions (as right or left, up or down), of form (as round, square, hexagonal, or again leaf-shaped, heart-shaped, etc.), of size (as large and small), of distance (as far and near), of solidity (as flat or solid, or variations in depth in the third dimension), and finally of motion (as moving or at rest). This analysis might be carried farther, resulting in fewer factors at the expense of convenience. This answers the question, "What kind of information is thus given?" The answer to the method by which we receive them involves the separate treatment of each problem.

It is further true that we may obtain these space-perceptions from the eye at rest or in motion, from the single eye or the two eyes. It is further the case that no neiv perception is added by the more elaborate visual processes; and it is likewise true that (with the partial exception of solidity) there is no form of information which is not obtainable through the single eye at rest. The difference is largely one of convenience, extent, and variety of spacial experience; but that means a great practical difference. It will be best to consider each of these factors of space-perception in terms of single vision with the eye at rest, and then observe the variations in the process due to the presence of binocular vision, and again of the movements of the eye.

Topic X. The Perception of Direction and Form. These perceptions result directly from the method of formation of the image. The perception of direction in the single eye at rest is determined by the position on the retina at which the image is formed. Owing to the inversion of the rays by the lens, the upper half of the retina corresponds to the lower field of vision, and the lower half of the retina to the upper field of vision ; similarly whatever I see on the extreme right in space falls on the inner half of the right eye, and what is to my left in space falls on the outer half of the right eye ; and again conversely, if I use the left eye alone. As all rays entering the eye cross at the nodal point, which is a little back of the center of the lens, it is easy to find the position on the retina of a point in space by simply connecting that point with the nodal point, and extending the line to the retina. Owing to this fixed relation, I come to associate definite regions in space with definite positions on the retina ; and this association is never seriously interfered with by the fact that I use two eyes, and that the eyes are in constant motion. A convincing proof of this fixed association is obtained by closing the eyes and pressing the little finger lightly against the eyeball on the inner (left) side of the right eye. This mechanical pressure will cause a dull illumination, which in turn will be referred to a region in space on the extreme right-hand side. It is thus easy to formulate the principle of direction. Objects above, like those on the ceiling, are associated with the lower part of the retina, and objects on the floor with the upper part of the retina, and so on. Direction is then due to the fixed association between position on the retina and position in space, the relation in turn determined by the inversion of the image under constant conditions.

The perception of form, or shape, is likewise determined by the formation of the image. The retinal image is a facsimile of the object seen. Its outline, or contours, will accordingly reproduce the outline or contours of the object, and this miniature will be accurate 'in light and shade, color, and form. The difference, then, between a square and a disk is in the combination of stimulated points. This convenient phrase summarizes the condition on which depends the perception of form. The accuracy of form-perception depends upon the accuracy of the mechanism of the eye in forming a sharp and distinct image. It has its limits in the power of the lens to focus for near, or in some eyes for distant objects; but given a clear image, the form-perception results. Here again, constant association through experience familiarizes and facilitates the rapid perception of distinctions of form.

It is difficult to arrange a test of the sense of direction alone, and not much .easier that of form alone, since both are so commonly involved with other perceptions. For direction, one might arrange in a dark room that a single pin-point of light shall appear for an instant, disappear, and then another reappear at a different place, and the subject be required to indicate the difference of direction between the first and the second points. For form, again, one might take a series of ellipses slightly changing the proportions of the two axes, and determine which is the more elliptical; or again, one might arrange very slight differences in irregular shapes, like inkblots, and determine how far changes could be detected. The test of the ellipses at once suggests that size, in the difference between the vertical and horizontal axes, would enter, and again that the difference between one curve and another is merely that of a difference in the arrangement of change of direction. Thus a straight line is a line that does not change its direction, and a circle is one that constantly changes its direction. None the less, direction and form, though commonly combined with other space-perceptions, are sufficiently distinct to be separately considered. Though expressible in terms of direction, form is a simple perception.

A special problem arises from the inversion of the image, and it might be supposed that to see an object erect with an inverted image requires explanation. Since, however, the whole process is a matter of association, it is just as easy to learn to associate the lower part of the retina with the upper part of the field of space as vice-versa. The demonstration given in the class showed that by means of casting a shadow on the retina, we can prove that an erect image (for the retina does not recognize the impression to be a shadow, and treats it like an image) would be projected and seen inverted.

Topic XI. The Perception of Size and Distance. While the perceptions of form and direction depend wholly upon the position and distribution of the retinal image, the perception of size depends upon it primarily but under the assumption that other relations are constant. It may, then, be said that, other things being equal, the size of the retinal image will be a sufficient clue to the size of the object. Of two objects at the same distance) from the eye, the larger will throw an image upon the retina proportionately larger than the smaller one. It is, however, obvious that other things as a rule are not equal, and that primarily the one factor making distance and size relative judgments — indeed relative to one another — is the fact that size varies with distance and distance with size. We are thus compelled to speak of the apparent and the real size of an object.

The figures shown on the blackboard illustrate how a set of objects may all be of the same size, but at different distances from the eye, and accordingly have images of different sizes; or again that three objects of different sizes may be so adjusted in their distances from the eye that all three, the nearer, the middle, and the farther object, may have a retinal image of precisely the same size. In practice, accordingly, we can distinguish three types of problems: First, with objects at the same distance, to judge of their relative size. For this the size of the image is adequate. Second, for objects at a different distance but known or assumed to be of the same size, to judge of their relative distance. Such judgment of distance would in the one eye be accomplished by the" mechanism of accommodation, as will be explained presently. Third, and most usual, objects at different distances and of different sizes, to be judged at once relatively as to their size and distance. This complex problem, involving many factors, is the one in which we gain great proficiency.

Returning to the first problem, there is little to add, since, the determination of the distance of an object being somehow accomplished, the judgment of size depends upon the size of the retinal image. However this is often so complicated by movements of the eye, by differences in shape and in direction, that it still remains true that the perception of size is as a rule not simple. The point will be considered again in connection with the movements of the eye.

The perception of distance independently of size depends upon the feeling of the set, or amount of contraction, of the ciliary muscle, which in turn sets the lens to give an accurate image upon the retina. We may call this briefly the process and the feeling of accommodation. It has its sensory counterpart in the blurredness of the image, which we disperse by changing the accommodation and thus sharpening the image. In a familiar space and within short range, say twenty feet, the shifting accommodations in order to produce clear images would sufficiently determine judgments of distance. Since both size and distance are relative and can be expressed in terms of changes of angle of vision, it follows that a much smaller change of distance at a nearer range will induce as much feeling of change as a considerably larger change of distance at a larger range. To move the finger away an inch or so at a distance of five or six inches involves far larger changes of accommodation, as well as of size of retinal image, than to move it an inch or two at a distince of twelve inches. But for every successive foot the difference in set (and in size of image) rapidly diminishes. It has been calculated that the changes of accommodation substantially stop at twenty feet, and further that within this distance the .reading distance of ten or twelve inches covers the largest changes of accommodation.

The combined problem of judging size and distance jointly is one that requires large experience to solve, and which under unfamiliar conditions we often fail to solve accurately. Experiments in the dark room show that the ordinary judgments of the distances of objects are complex, the judgment depending on their known size, on their relative position tot one another, on the cutting off of images, on the way in which the objects catch and reflect the light, and on other details. It is only when these are eliminated that we get a clear notion of the power to judge distance and size by the combined processes of size of image and of accommodation. It may be added that the question as to which factor leads in the joint process, or which step is first taken, again depends upon circumstances, and possibly individual habit. Do we first judge the distance and then determine the size, or get the size and then determine the distance? The most generally correct answer is that we shift from one to the other, and by mutual adjustment clear up the size and distance together. In this process the eyes may readily be deceived, and illusions of judgment result. This problem will be further considered under ' ' Binocular Vision. ' '

Topic XII. The Perception of Solidity. The nature of this perception is easily defined, but the variety of its appearance complicates the problem. It refers to the third dimension of objects, as well as to the relation of the parts of an object in depth, thus including perspective. At the simplest, the distinction is between a flat and a solid, and as illustrated between a disk and a hemisphere. Neglecting the matter of light and shade, and still considering vision with one eye at rest, the disk is distinguished from the hemisphere because all parts of the disk require the same accommodation, while to see the center of the hemisphere clearly requires a nearer accommodation than to see its edges clearly. If the hemisphere were a hollow half-ball, then focusing for the edges would require closer accommodation than for the center. Similarly for the skeleton pyramid as held with the larger square nearer, thus looking into the pyramid, or with the smaller square nearer, and looking down its sides, the retinal images of the single eye in the two cases may be precisely alike, yet the two appearances are instantly distinguished, and this again by the difference in the shif tings of accommodation. Such is the perception of solidity at its simplest.

Topic XIII. Vision with Two Eyes. The further consideration of solidity involves binocular vision. The first problem is the question of seeing singly with the two eyes. Clearly the images on the two retinae as formed by a single object are related ; and when the eyes are directed towards an object, the image thereof falls on the fovea of each eye at the same time. This process is called fixation, and is popularly called "looking" at an object. It is accomplished by a movement of the internal (or external) muscles.