Omissions, Difficulties and successes of the Gestalt theory of perception

Such then, is the present situation with respect to the gestalt theory of perception. In casting up the account we can’t, of course, undertake an appraisal of the gestalt system as a whole. But the agreement of the theory with facts in the realm of its own phenomenological formulation is excellent.

The researches of Kohler and Held on brain potentials in object-vision are suggestive but they do not carry us very far. In direct brain experiment, definitely adverse finding have appeared. It is fair to say that gestalt theory needs a support from psychological fact with the facts thus far have stubbornly refused to give.

On the score of the completeness of coverage of perceptual phenomena there are some notable omissions. Configurational experiences are in general well handled, and the phenomena of frame of reference also receive attention.

Kohler, in permiting his brain field to be topological rather than tied to proximal stimulus-dimension, has escaped the error of literal brain topography.  But the percept, in constancy phenomena, is fairly representative of the distal object.

Sensory qualities and dimensions seem to have been slighted in the gestalt theory of perception. Much has been said about the fact that they are affected by field changes and are subservient to the laws of the whole, but these statements do not do them justice.

They cannot be explained by isomorphism since they are merely continuances or spreads of a homogeneous quality or dimension, and they are without form or articulation.

Kohler has made an attempt to relate them to specific energies by way of chemical differences in the brain, but so far there is not much evidence for the view.

Perceptual set is recognized by gestaltists- it is even included among Wertheimer’s principle of groupings. But it does not seem to have been well integrated into the theory.

There are still further difficulties that bear upon explanatory significance. The neurological picture of the brain gives us everywhere a specificity of elements; we look in vain for something that would correspond to macroscopic fields or wholes. This fact in no way detracts from the truth or importance of the gestaltists demonstrations of a unique “whole character” in perception. The failure of the psychological and anatomical facts to conform only makes us appreciate the difficulty of the problem.      

Kohler’s theory

Wolfgang Kohler (1887-1967) was a founder of Gestalt theory. The key concept in Gestalt theory is that the nature of the parts is determined by the whole - parts are secondary to the whole. When we process sensory stimuli, we are aware directly of a configuration or overall pattern which is grasped as a whole. For example, when listening to music, we perceive a melody rather than individual notes, or when looking at a painting, we see the overall image rather than individual brush strokes. Köhler emphasized that one must examine the whole to discover what its natural parts are, and not proceed from smaller elements into wholes.

Kohler proposed the view that insight follows from the characteristics of objects under consideration. His theory suggested that learning could occur by "sudden comprehension" as opposed to gradual understanding. This could occur without reinforcement, and once it occurs, no review, training, or investigation are necessary. Significantly, insight is not necessarily observable by another person.

According to Hothersall 1995, Kohler tested Gestalt theory in regards to the transposition of stimuli by training a chicken to distinguish between two shades of gray. The chicken was then rewarded for pecking at the darker gray card but was not rewarded for pecking at a lighter gray card. After numerous trials, the chicken only pecked at the darker gray card. When the chicken was exposed to a dark gray and a black card, the chicken pecked at the black card. This experiment disproves Throndike's theory that animals learn to respond to a particular stimulus with a specific response.

Methods of adaptation level

According to Helson 1947, the subject-observer was told that he would be present with two weight I succession. After lifting the second weight he was to give a judgment of it by stating to which of the following categories it belonged;

Very, very heavy

Very heavy

Heavy

Medium heavy

Medium

Medium light

Light

Very light

Very, very light

The subject was further told that after he had judged a number of weights he would be given another set with he would judge in like manner. After a number of observations had been made he was cautioned; “be sure you judge each weight as it is and not as you think it should be”. It will be seen that there was no absolute categorizing of the meanings of the end terms or the medium of the scale. The subject was left free to interpret them as he wished. The results were presented as the average judgment of a group of subject. It should be noted, that although in presenting each stimulus a comparison or standard stimulus was also given as in psychophysical experiments, the judgment made the subject was not, as in psychophysical experiments, a comparison between second and the first stimulus, but was in term of the absolute scale for second stimulus alone, as above shown. The role of the comparison stimulus was provided for in the predictive equation. It was treated as one of the item that makes up the pool from which the adaptation level is established.

      

The mathematical procedure for handling the data of the experiment was developed from another work of the author in the field of brightness vision. That method, as applied to the brightness dimension, involved the taking of a weighted logarithmic mean of all stimuli and background in the field times a constant. For the visual problems the formula found to be adequate was as follows;

AL=K(A3/0A-)1/4

Where Al is adaptation level, K is a factorial constant, A0 is the brightness of the background, and A- is the logarithmic mean of the brightnesses of the sample on the background.

Helson’s experiments were also addressed to the testing of a number of additional theorems deduced from the general theory. These included the following deductions;

1. The predicated equivalence of absolute and relative methods for determining the adaptation level when the comparison stimulus is chosen at account the log mean of the series.
2. the minimum stimulus effective as a standard in shifting the adaptation level
3. the greater effect of a stimulus upon adaptation level when it is used as a standard than when it is used a member of the series
4. the predicted effect of various types of stimulus distribution
5. The effect of practice and past experience.

 Later he derived the formula

∆A = k(X1 + A)/2

Where k is Weber constant (p. 70) and X1 is particular stimulus

Meaning and Exemplification of adaptation level; theory of pooling and weighting

Helson criticizes current perceptual theories for their lack of the quantitative formulations that are necessary for the mature development of any science; and he suggests his method and theory may help to supply this need. One of the salient characteristic of organism, he maintains, is the tendency to categorize their experience in terms of some kind of order.

The way in which the organism achieves such an order is by establishing subjectively some neutral, indifferent, region in its quantitatively arrayed experiences. Using the whole gamut of stimulus magnitudes to which he is accustomed as a frame for his judgments, the individual established an average really a small region of magnitude, as kind of standard. Such a neutral region in the hefting of weights would be the small range of objective weight values within which the subject reported that the weight seemed neither heavy nor light but medium. This neural or medium position is called the adaptation level of the subject.

For every moment of stimulation, in Helson’s view, there is an adaptation level; and this level changes in time and with the varying conditions of stimulation.

Pooling; pooling is therefore a physiological as well as a psychological phenomena; it may occur even below the level where conscious judgments occur.

According to Eiser 1986, Helson defines adaptation level as a weighted logarithmic mean of all past and present stimulation on a given dimension. As each new stimulus is presented, it will be averaged into the computation on a new Adaptation level. 

What do you meant by perceptual norm and frame of reference?

The sensory experiences studied in psychophysics are stimulus-bound. They are based on discriminations of small intervals in a definite, controlled series of stimulus-presentations; and the capacities for the quantitative judgments required are considered as somewhat standard, that is, as pretty much the same for everybody, and as dependent upon fairly stable physiological conditions. From a phenomenological standpoint, however, dimensionalities in perception may occur that are not so closely bound to the immediate stimulus. No one can directly control or measure a percept. It has a right to be of any magnitude the individual experiences it to be; and the experience of its magnitude may at times vary considerably from what one might expect from measuring the magnitude of the stimulus. This does not mean that no measuring scale is being employed. It means only that the scale in use is, to a large extent, observer-involved. In such a situation perceived magnitude or intensity may depend to a large extent upon the subject's past, his immediate past chiefly, but also on his more remote past. It will depend also upon his range of experience with magnitudes or intensities in general. 

The prevailing set or state

It is an aspect of perception in which individual differences as well as differences in the state of an individual at different times, play an important role. It has long been known that particular sets of the individual or attitudes, either long standing or momentary affect the selection of the objects that will be perceived. Phenomenologically they also result in a greater attentive clearness or vividness of those objects. To this aspect of perception the concrete object character of the stimulus is especially relevant, for when we take the character and meaning of the object into account we can often see a relation between it and the state the individual is in. The phenomenon is most clearly shown with respect to objects that we are looking for or meaning that we are seeking to realize from stimulus-situations that are undetermined or vague.

Perceptual sets or readinesses induced by needs are both common and important. Emotional states may also determine perceptual readiness or the manner in which we perceive certain objects or relation. An illusion in which, on a dark night, one sees a tombstone in a cemetery as a ghost is a timeworn example. The way in which indefinite or ambiguous things are perceived may to some extent be influenced by the individual characteristics of the perceiver, a fact implied by the use of the Rorschach test for personality diagnosis. However, overlook the fact that the set to perceive may often be based not upon any strong motivating, emotional o personality edition, but upon nothing more dramatic that the frequency and familiarity of the object in the observers experience.       

Concrete objective character

It is a universal aspect of perception that will seem almost too obvious to mention. It is quite distinct from any of the aspects we have described, though it is related to them. Though it is not necessary to do so, let us approach the matter by beginning with sub threshold conditions. Suppose we are looking at some object, with a view to identifying it, under very brief exposures in a series of trails are then gradually lengthened or the illumination is gradually increased. We see at first a kind of reddish blur having a roundish form, but identification of the objects does not come. Exposure or illuminations are further increased and we try again. A number of trails without success or with misperceptions may occur. Then all at once, we recognize it. It is an apple. It is not a red circular disc, it not a beet or round red ball- but an apple. We can not say it is just color experience. It is not adequately characterized by its configurational or wholeness properties alone.

This aspect of perception is so universal and characteristic that it would be hard to find anything regarding the appearances of things that is more significant. Things and event appear to us not as mere qualities, dimensions or forms but as things and event. Concrete object character as we shall call it is a fundamental property of practically all our perceptions. 

Dimensional Frame of Reference

A fourth class of aspects appears when we are faced by the problem of giving absolute dimensional judgments concerning the members of a series of stimuli. This feature is not to be confused with sensory dimensionality as it was discussed in our first category where for example, brightness or loudness were estimated with reference to some objective standard. The aspects we are now considering refers, rather to the question of what we call bright or dull light or heavy loud or faint and the like with respect to stimuli that we experience. Suppose for example, that we are presented with a lot of circular discs of the same size, one after the other. Let the discs, however, be in the form of spots of light thrown on a screen and differing over a fairly large range in brightness. We are to judge for each disc whether we consider it to be bright or dim or medium. Though no standard of reference is given, there will probably be determined, after series of stimuli has been presented, a degree of brightness that looks to the observer as neutral that is a degree above to be dim. The individual, in other words, forms his own subjective scale of judgment. We shall call this phenomenon the dimensional frame of reference.

Perceptual constancy

Suppose now there is presented a circular disc, first directly before us in the frontal plane where it is of course seen as circular, and then in a position titled away from us so that the image it produces on our retinas is elliptical in shape. We still tend under the latter conditions to see the disc as circular, not as elliptical. We do not however, see it as perfectly circular, but as a compromise that favors the circular more than the elliptical form. This is the phenomenon of perceptual consistency. It preserves for us consistency of appearance and thus the means of recognizing and identifying objects when they are seen at different angles or in different distances and of colors and brightnesses under differing conditions of illumination. Cues given by the object and surroundings enter intimately into perceptual constancies. There cues seem to be utilized in agreement with past experience and for the most part they give us fairly veridical perceptions. 

Figural or configuration aspects

Our second class of perceptual phenomena contrasts sharply with the first. Though like those in the first they are experiences arising from things in the environment, they seem even less determined by the stimulus and more determined by processes inside the organism. They exhibit strongly the effect of one thing upon another in the perceptual manifold, an effect which frequently produces optical of other illusions. They are concerned mainly with the formal properties of the thing we perceive, such as shape, outline, grouping, and the like. Looking at a circle drawn with ink on a white card, we note that the appearance of its size is altered if it is placed between parallel lines or enclosed in an angle. It can be made to appear distorted into part of a spiral by a twisting line along its course and by special features in the background. A square turned up on one of its corners looks quite different fro the way it appears when its upper and lower edges are in a horizontal position. Looking at the drawing of the circle again, but without accompanying lines or angles, we see that it encloses an area that is segregated from the surroundings, and that the line of the circle itself is a contour that seems to belong to the circle as its edge and not to be the edge of a circle hole in the background. We see that circle appears as a definite “figure” standing forward clearly and that the rest of the card seems to extend beneath it as a less vivid ground.

Figure and ground are ubiquitous aspects of perceptions.  In every sense modality our word consists of figures appearing against grounds and where other aspects are not in control there are a number of rules that determine which part shall be figures and which ground. In drawings in which either portion may serve as figure or ground there is usually a shift of the percept back and forth from one figure-ground experience to the opposite.          

Sensory quality and dimension

First a small paper disc is shown on a white background. We notice that it appears red. Another disc is shown which looks blue and so on. A certain experienced quality. The tone we hear, the smell of a rose, a taste, a pain, an experience of pressure, warmth or cold are other familiar examples. We also observe that the quality has associated with it certain quantities or dimension. In vision, at lease the quality is spread out or extended, it seems to occupy space. Related to quality we have also the experience of intensity or of strength.

One gray disc looks brighter or darker then another, one red is stronger than another. Qualitative experiences also endure through time. Sensory qualities and dimension, therefore, constitute one general aspect of the way things appear to us. It is true that these qualities and dimension are often modified by the conditions or surroundings under which they are observed, such for example, as background and illumination. They may interact with one another in many ways, but the existence of qualities can never be fully accounted for by this interaction.

There has been some difficulty with classification and terminology in this field. Looking at the matter from the standpoint of pure conscious awareness Titchener regarded sensation as elements of consciousness and quality, intensity, extensity, duration and clearness as attributes of sensation. It seems better, perhaps, to-regard not sensation but the experience of quality as a basic fact in our awareness of our world, a fact contributed by the process of the organism itself to the energies received from the stimulus.             

Phenomena of perception

Perception is the state of being aware of something through senses, it is therefore an image that reflects on mind and stimulates memory. The phenomena of perception can be classified for our present purpose under six heading. The six broad classes of perceptual phenomena are below-

1. Sensory quality and dimension
2. Figural or configuration aspects
3. Perceptual constancy
4. Dimensional Frame of Reference
5. Concrete objective character
6. The prevailing set or state

Is perception innate or learned? Give the empirical evidence in support of your views

A theme running throughout the study of perception since the time of the ancient Greeks has been whether perceptual processes are learned or innate. Innate means existent or potential at birth due to genetic factors. Learned means that the ability is based on remembered past experience with similar or relevant stimuli.

One way to test these ideas is to examine humans or animals that from birth had no visual experience, and thus no opportunities for visual learning, and to test them when their sight is restored. Perceptual functions are then tested to see which, if any, are intact. This was done with human beings born blind because of cataracts before surgical methods were developed to safely remove them. Cataracts are a disease of the eye in which the crystalline lens or its capsule are or become opaque. It was found that after their cataracts were removed they were normally responsive to changes in color and light, but they were unable to tell when a figure was present, or to discriminate between simple shapes. It took a period of two to three months before they were able to perform these tasks with ease.

Along the same lines, research with animals deprived of visual experience from as close to birth as possible, finds that even without visual experience, some of the animals can perceive visual depth cues. Research also finds that animals raised without opportunities to see (for example if reared in the dark) sustain long-lasting deficits in their perceptual abilities. Indeed, such deprivation can even affect the weight and biochemistry of their brains.

Studies with human infants find that at even one or two days of age, they are able to perform detailed visual discriminations, and they show preferences for visually complex or novel stimuli. While this line of research cannot prove the ability is not learned, it does lend support to these abilities being present at birth in some form.

In sum, it seems that while some fundamental visual perceptual abilities are innate, visual experience is necessary to maintain and further develop them.