Discussion 0. How I see words in my head. A Visual Workplace is not about buckets and brooms or posters and signs or a handful of metrics. Boelhius, wrote: ;'for sighl is common to aH morta1s. There was much evidence lo the contrary Ihe snake catled lamia is seen daity by the rustics attnlcling 10 ilsetf wilh fix. O halch Iheireggs by looking al thern. Nol lO mention Ihe maidens. The organismo 10 whese needs vision is geared. When something appears or di sappears. The mosl primitive organ of sighl.
To contemplate immobile parls of lhe surroundings is more nearly a luxury. Change is absent in immobile things bul al so in things repeating the sume aClien over and over er persevering in it steadfast ly. The constant factors of a visual set- ling, e. When a person is foreed to stare al a given figure he will use any opportuoity lO change il by varying il: he may reorganize the grouping of its parts or make a reversible figure switch from one view O the other.
A color looked al steadily tends to bleaeh, and if the eye is made lO fixate a pattern without the small scanning movements that are never absent otherwise.
These reaclions to monotony go all the way from conscious defense O Ihe purely physiological wearing off of impulses gener- ated in the brain by a static situation. They are an elemenlary form of inlelligenl conlempl for indiscriminate attention. Noticed and at- tended lo is only what matlers. One refuses to be bored. Practically usefuJ though this selective attention to change is.
It makes it difficull lo become aware of the constan! This weakness shows up when the thinker or scientisl needs to consider agents Jying beyond Ihose that display observable change. In physical as well as in psychological or social malters, the constant aspects of a situation are most easily overlooked.
The characteristics of per- ceplion nOI only help wisdom, they al so reslriet iI. The eyes are movable within their sockets. Even the recording processes going on within the eyeball are highly selective. For example, since Ihe early years of the last century there have been good reasons to assume tha! This assumption, by now confirmed experimentally and anatomically, means to us that the pholochem- istry of the eye proceeds by a similar kind of abstraction by which.
Through this ingenious simplifica- tion vis ion accomplishes wilh a few kinds of transmitters a task that would otherwise require an unmanageably large number of them. We were accustomed lO believe tha! Ihe retinal receptors know of no such dislinclion. AI1 they could do was supposedly 10 register shades of color and brighlness, so thal il was left to the brain to nfer Ihe presence of movemenl from a computalion of changes occurring in masses of point-sized SpoIS.
By now, Ihe retina of the frog's eye is known lo conlain al leasl four types of receptors, responding each lo one special kind of stimulus and remaining unimpressed by alJ olhers.
Among Ihem are the "bug-detectors," which reaCI immedi- alely and exc1usively lo small crawling things. Others are geared to respond only to he movement of, or encounter with, edges OrlO Ihe onsel or end of illuminalion. In order lo accomplish these reaclions, large groups of receptors must cooperale as a leam because only in Ihat way can lhe shapes or mo- tions of extensive stimuli be apprehended. This means Ihal even al the retinal level there is no mechanical recording of elements.
II is true. Ihal like all screening, Ihis one expedites the processing of the material bul al so limits operations 10 what remains available after the screening. When a frog starves in the presence of dead. Such inbuih selectivity is useful not only because it avoids Ihe wasling of elfort bul also because, by reslricting the choice, it makes reactions faster and surer.
Striking examples of such highly selective behavior have been described by ethologists, notably Konrad Lorenz and N. Since animaJs cannot tell us what they see, we cannal be sure lo what extent the selection takes place in their perception tself ar rather in their responses to what they perceive. In any case, no stimulus can be reacted lo, unless it is distinguished in percep- lion. Most probably, lhis distinction is nol a malter of specifically primed categories of retinal receptors like those making the frog respond to crawling bugs.
The responses lo Ihese signals. The yellow bill of the herring gul! When the red spot is absent, the chick does not peck; when the chick does nOl peck, the parent does nol deliver the food. Signals of this kind meet two essential prerequisites: they are clearly identifiable by their pure color and simple shape, and they are sufficiently distinct from what el se is commonly visible in the environment.
The perception of these animaJs must be geared lO their highly selective responses. Their visual fields are likely to be hierarchic rather than homogeneous, in the sense that certain perceptual fea- lures stand out because of the needs to which they relate.
The ani- mal could nol respond lo them unless they were distinguished per- ceptually. This is an early instance of abstraction. Fixlltion solves l problem As long as such mechanisms are buih in by heredity, they rigidly apply to the species as a whole. At biologically higher levels, the choice of slimuli and the reactions to them are increasingly controlled by the individuaJ. The eye movements that help to select the targets of vision are somewhere between automatism and willful response.
Bccause retinal sensitivity i'i so restricted. This means taking up one thing al a time and distinguishing Ihe primary objeclive from ils surroundings. An object may be.. Al early organic levels.
When a slrong light enters Ihe visual field. Thc response is steered by Ihe slimulus rather than by the initiative orthe observer. How is ocular fixation accomplished?
An act of fixation can be described as a move from tension to tension rcduclion. The sti mulus enters the visual field eccentrically and thereby opposes the field's own center wilh a new and alien one.
This connict between Ihe in truding cuter world and Ihe order of the inner world crea tes a ten sion. Ihus adapting Ihe inner order to the outer. Thc relevant ilem of the outer order is now ccntnllly placed in the inner. Herc we have an clementary example of slill another aspect of cognitive behavior. AII problem solving rcquires a restrucluring of a given problem situalion.
In ocular fix alion. Ihe restrucluring needed is of the simplest kind; it is nOlhing more Ihan a shifl of the center of orientation, nol requiring any re organization of the perceptual panero itself. I shall soon give examples of problem solving by much more como plex rC'ilructuring. Bul even lhis simple example why prob- lem solving not be.. He asserts thal we do nol speak of behavior as being intelligent when human beings or animals attain their objective by a direct roule which derives naturally from their own percep- tual organization.
Bul we tend to speak of "intelligence" when, circumstances having blocked he obvious course, the human being or animal takes a roundabout path, so meeting the situation.
The mechani sm of fixation does arise naturally out of the organization of the human being or animal. And yet the shifting of the center of vis ion to the center of interest seems to me to involve, al an ele- mentary level. In both cases, the st ructural connections within he given perceptual pattem are changed in a way that yields the solution ofthe problem. The simple example of ocular fixation serves also to illustrate another point of more general relevance.
The stimulus oflhe light entering the infant's range of vis ion gives a definite, objective struct ure lO that field.
The field has a center. This discrepancy produces the tension to which the child reacts by adapting his fixation to the structure of the outer situation.
Such an interplay between the struc- ture of the given field and the demands of the observer's needs and interests is characteristic of the psychology of attention.
Williarn James, writing about attention, suggested the opposite when he wrote that without select ive interest experience would be an utter chaos. BUl truly chaolic or otherwise unstruclUred situat ions are nol typi cal, and when they prevail Ihey make it all but impossible for selective inleresl to take hold of a targel. When Ihe fie1d is homo- geneous, as in total darkness. This sort of situation is nOI charactenstic of cognitive processes. I have shown Ihal Ihe need and opportunily 10 select a largel exists in cognition even at the retinallevel.
Since acute vis ion is limited to a narrow area. It facilitates the intelligent practice of concentrating on sorne topic of interest and neglecling what is beside the point of attention. If he close-up view is sharp. Ihe back- ground is blurred, and vice versa.
This selecliveness is contrib- uted by Ihe crystalline lenses of the eyes. The accommodation of the eye lenses is an ele- menlary aspect ofselective attention. The depth dimension contri bu tes. It makes the size of objects variable and Ihereby adaptable to the needs of Ihe observer. This is so because Ihe objecl of perception does nol enter lhe eye bodily. Democ- ritus, for example, he Id that in perception a sort of decal of the object's outer sulface enters Ihe eye through the opening of the pupil- which posed the problem of how a large object could shrink sufficiently lo accomplish such a feal.
We know now that what he eye receives is not a part of the object itself bul an equivalent of it. The size of the projeclive image depends on the distance of the physical objecl from he eye. Therefore, by choosing the propcr distance, he observer can make lhe image as large or small as his purpose requires. In order lO be comfortably visible the relevanl portion of he visual field muSI be large enough lo be sufficienlly discernible in its detail and small enough to fi into the field.
Further- more, the size of the critical area also determines how much of ils surroundings will be contained in Ihe visual field at he same time. The smaller he area. The proper choice depends on the nature of Ihe cognilive task. How much detail is relevant? How much of the conlext is pertinent lO the understanding of the matter under scrutiny? Here again the correct selection at the ele- mentary perceptual level is an important part and reflection of broader cognitive strategy.
To find the appropriate range of a prob- lem is almost tantamount lo finding its solution. This strategy of thought may be hampered at its very foundation when the visual range of the situaton to be contemplated is incorreclly chosen. In praclice Ihis means, for example, Ihat the visual aid offered by an iIIustration or a television mage may be severely impaired simply because the size and range ofthe portrayed objects are inappropriate.
Since reasoning aboul an object starts with Ihe way the object is perceived, an inadequate percept may upsel the whole ensuing train of thought. SIllIpes are cOllcepts In the perception of shape lie the beginnings of concept fonnation. Whereas the optical image projected upon the retina is a mechan- ically complete recording of its physical counterpart.
The perception of shape is the grasping of structural fealures found in, or imposed upon, the stimu- lus material. Only rarely does this material conform exactly to the shapes il acquires in perception. The full moon is indeed round. Bul mosl of the things we see as round do nOI embody roundness lilerally; they are mere approxi- mations. Nevertheless the perceiver does nol only compare them with roundness but does indeed see roundness in Ihem. Perception consists in fitting the stimulus material with templates of relatively simple shape, which I call visual concepls or visual categories.
The simplicity of these visual concepts is relative, in Ihal a complex stirnulus pattern viewed by refined vision may produce a ralher inlricate shape. What matters is Ihat an objecl al which someone is looking can be said lO be truly perceived only to the extent to which it is fitted to sorne organized shape.
In addition, there generally is an amount of visual noise. There are known to be inbred responses to certain shapes.
But these mechanisms presuppose rather than explain shape perception. The red spot al he mandible or the sea gull must be apprehended as such before it can be reacted too The same would hold for Jungian "archelypes. It is rue that Ihe above-cited discoveries about the frog's sense of vision imply thal some organization into larger unils exists even al the relinal level. If the smallesl initialor of the slimulalion is nol a dol bul an objecl, such as a crawling bug or a moving edge.
Ihen a large panel of receptors mus! A dol cannOl report aboul an extended object. In other words. Ihere seem lo be responses lo shape ralher Ihan mere recordings of elements. BUl responses lO shape do nol necessarily imply con- scious perception of il; and even in the higher vertebrales similar mechanisms are likely to be rigid 10 amount 10 more than a kind of shonhand abbrevialion of sensory recording.
In order lO accounl for Ihe complexilY and flexibilily of shape perception. The shape patterns perceived in Ihis fashion have IWO properlies enabling them lO play the role of visual concepts: they have gen- erality and they are easily idenlified.
Slrictly speaking. There may be only one objecl to fit Ihal pallern or Ihere may be innumerable one". Even Ihe image of one panicular person is a view of a panicular patlern of qualilies, of Ihat kind of persono There is, therefore, no difference in principie between percepl and concept.
In order 10 be usefu!. The biological releasers can serve here again as illustration. They tend to be simple, distinct colors. One cannot recognize something as a thing known, expected, or lO be reaeted to unless ir is discriminated by its sharply defined charneter.
I am describing the perception of shape as the grasping of generic structural features. This approach derives from gestalt psychology.
There are other Iheories, notably the traditional view hat the sense of vison mechanically records the elements of stimulation, which are then suitably conglomerated into shapes on the basis of the perceiver's past experience. If the theory were true. Perception takes time Much recent diseussion of shape perception would lead one to believe that what matters mosl for its explanation is whether it occurs spontaneously. Most organic accomplishments go through a phase of learning and biologieal maturation.
What matters is what kind of leaming is nvolved. Is an nitial incapacity to see shape due to the lack of similar experience with which a present stimulus can be compared? Or is it the art of grasping the structufe of a visual pattern that takes time to perfect? Perceptual acquisition in the lalter sense was the subject of studies by German psychologists on what they called Akwalgenese.
One of their approaches was to reconstruct the elusive and often all loo rapid process by presenting a pattern insufficiently, e. Under such conditions, perception tends to start with a diffuse, undifferentiated whole. In order to show how little these processes resemble a mechan- ical recording of stimuli, I will translate Ihe summarizing statement of one of these researchers.
Gottfried Hausmann: The experimental silUtttion conveyed 10 Ihe observers Ihe clear conviction Ihal whal we popularly call perceplual cognilion cannol be described as a simple, immediate, purely sensory mirroring. Instead, it originates in a process of mani fold, mutually intenwined. The course taken by such a process may be eilher organically consequent or intricale. Sometimes fancy will leave the gjven dala behind, bUI when Ihe process runs organicaJly.
Geslalt psychologists. What is Irue of shape. I menlioned earlier Ihat physiologically the many wavelengths of lighl corresponding lO differenl shades of hue are dealt with by a few types of receptor, each sensitive to one color or a range of colors. In the psychological realm. JUSI as perceived shapes are more or less complex elaborations of simple shapes.
Here and Ihere. Sorne of these com- binations are sufficiently precise in Ihemselves to function as visual concepts in Iheir own right. In the system of colors. Ihese secondary concepts serve as transitional links between the primaries. There is considerable evidence to indicate that the graspability of shapes and colors varies, depending on the species, the cultural group, the amount of training of the observer.
What is rational for one group, will be irrational for another, i. There are differences in this respect between different species of animals, between man and ani- mal.
A rat does not seem to perceive the difference between a circle and a square. For sorne per- sons, a pentagon is a perfectly graspable visual figure whereas it is a roundish thing of uncertain angularity for others. Children have trouble with the identification of certain colors, which have a clear character oftheir own for adults. Sorne cultures do nol put green and blue under separate perceptuaJ headings. Within iimits. The task is that of developing devices that can read such shapes as letters or numhers.
What is invariant about a 3 or a B must be picked out, regardless of the particular shape it takes. The machine Slarts out by doing exactly what Ihe eye does: it cut s up the continuous stim- ulus pattern into a mosaic of discontinuous bits, each recorded by a separatc photoeJectric ceH. This is an act of so-called digital cod- ing, which transforms the stimulus into an assembly of di screte units, each reportng the presence or absence of a particular oplical quality.
The mosaic preserves or indicates no pattern whatsoever, except that the dots are nol scattered at random but mainlain their particular location relative 10 their neighbors.
Putting all similar elements together and separating them from dissimilar ones, the machine obmins a rough pattem, which then it can be asked to clean up by eliminating small irregularities, dropping isolated particles.
This is the sort of blnd fitting togelher of pieces which does nol go beyond discover- ng similarilY or dissimilarily among adjacent elements and in which Ihe resulting shape comes as a surpnse-ralher as though a child were to draw a line along numbered dOls and find Ihat il adds up 10 the outline of a rabbit. In Ihis procedure shape is derived from the analysis of the pat- terno Bul the machine can also be handed certain shapes ofwhole or par!
This sort of codification works by analogue, Ihat s, il compares shape with shape. Here a pre-establi shed concept is rigidly identi- fied with one particular realization. It is a melhod Ihal works well when Ihe task is limited to the reading of a slandardi zed sel of shapes, for instance. The syMem will allow for a certai n amount of broadmindedness in Ihat Ihe machine can be made lo measure the amount of area which a given patlern has in common with a givcn templale.
In this way. Change of size is one of these dimensions: change of proportion. Ihat is. When allowance is made for rotatian in space, a diamond may be recognized as a square turned A more radical transformation is the tilt that changes lhe angles. Such flexibility makes it possible for the machine lO isolal e the "opologi cal" properties-such as louching. When the task ealls for nothing better than identication by what- ever means.
We may identify a person by nothing more than Ihe ring he is wearing or by his name. Rats seem 10 identify sorne pattems by simply diseovering a certain comer in a particular loeation. A scanning machine may slide a nar- row slit across a blaek shape and thereby identify it through a se- quence of slices of changing lenglh without any realization thal the panern is the profile silhouette of a human head.
A brain-i njured per- son suffering from agnosia may identify a reetangle by eounting the number of eorners. For most practical tasks, however, il is necessary to understand the overall visual struclure of an object to be handled, and for the purpose of the scientist or artist a grasp of the object's visual charaeter is essentiaL In principie. Chinese ideographs are a greater challenge than the Roman alphabet lo practice. Numerals and letters, for example, have evolved histori- eally as the results of the search for seIs of shapes simple enough to be easily produced, perceived, and remembered, yet as cJearly dis- tinel from each other as possibJe.
Nature accommodates this need for simple shapes essentially in two ways. They come about in evo- ution as signals for organisms endowed with the sense of sighl. Quite independently from sight, the tendency towards teosioo re- duetion in the physical world will produce the simples! Even so, most of Ihe shapes and combinations of shapes presented to the eyes by nature are much more complieated than letters.
In maoy such instances. A box. This means thal perceptual organizalion does not limil itself to the material directly given but enlists invisible extensions as genuine parts of the visible.
What happens here is not thal Ihe be holder com- pletes by non-visual knowledge Ihe fragment he actually sees. Herc again invisible parts of the object supplement the visible ones in arder to produce a complete shape. The distinction between complete and incomplete shape as well as the pertinent rounding off take place wilhin perception itself. B P R Figure I The cognitive feat nvolved in such a process consists in rejecting the wholeness of a shape that presenls itself and in re-inlerpreting il instead as a part of a larger and structurally betterwhole.
Examples of similar procedures in scientific problem solving and everyday reasoning witl come readily to mind. A particularly striking example of shrewd restructuring by com- pletion in perception can be found in the phenomenon of trans- parency. Suppose a pattern consists of Ihree shapes, a red one. The distribution of colors suggests an order based on three separate, contiguous units. The character of the shapes sug gests two overlapping units.
How can this ntrinsic confiict be brought to a satisfactory solution? If the color of the central unit is reasonably accommodating, i. It will be seen as two colors, one behind the other-a transparency effect. This ingenious soluton adapts lhe order of the colors to the order of the shapes. In this case the perceptual solution of Ihe problem tends to presenl itself with great immediacy, and there can be no question but thal Ihe intelligent rearrangement of an unsatisfactory stimulus organization occurs in the act of perception itself and not in sorne secondary elaboration of the perceptual product.
Under natural condtions, vision has to cope with more than one or two objects at a time. More often than not , lhe visual field is overcrowded and does not submit to an integrated organization of the whole. In a typical ife situation, a person concentrates on sorne seJected areas and items or on sorne overall features while the slruclure of the remainder is sketch y and loose. Under such circumstances, shape perception operates partially.
It is in works of art. When an artist chooses a given site for one of hi s landscapes he not only selects and rearranges what he finds in nature; he must reorganize the whole visible matter 10 tit an order discovered, in- vented, purified by him.
And jusI as the invention and elaboration of such an image is a long and often toilsome process, so the per- ceiving of a work of art is not accomplished suddenly. More typi- cally. When the exploration is successful, the work is seen to repose comfortably in a congenial structure, which iIIuminates the work's meaning to the observer. Such an ex- perience is [he purest and strongest example of chat active explora- tion of shape and visual arder which goes on when anybody looks al anylhing.
The Intelligence oi Visual Perception i Visual perception, I tried to show, is nOI a passive recording of stimulus material bul an active concern of he mind. The sense of sight operales selectively. The perception of shape consists in the application of form categories, which can be caBed visual concepts because of their simplicity and generality, Perception involves problem solving.
Next I 5hall discuss a somewhat more subtle per- ceplual operation. The size of a retinal projection vares. There- rore. For example, an object actually maintaining its size may be reported to the eye as changing il during movemenl. The same is true for shape. The retinal pro jection of an object vares depending on its locaton relative to the observer. There are other such perceptual modifications. The brightness and the color of an object depend in pan on the brightness and color of the source illuminating il and on the spatial location of the object relative 10 light source and observer.
Intertwined' though he two appear, one can attempt lo tease them apart, espeeially by watching the same object in different contexts and the same contexl acting on different objecls. The object under observation must. This can be done in two fundamentally different ways. The observer may wish to peel off the context in order to obtain the object as it is and as it be ha ves by itself. This may seem to be the only possible way of per- forming an abstraction.
Here lhe abstraclion. The two procedures serve different purposes. In spile of retinal variations and en- vironmental nfluenees.
There seems 10 be wide- spread agreement on Ihis, although there is sorne controversy on how Ihe feat is accomplished. Nevertheless this view is quite re stricted and one-sided.
This is evi dently true for the size of objeets. Since biological orientation requires a stable world in whieh objeets preserve their identity. There is. Most ofhe psyehologieal diseussions have started from the noti. Does the mind perhaps average alJ Ihe projections statisticaJly and settle for a median size? Surely not, because in that case a pad of writing paper would be seen roughly the size of a building since on the average the projections of both kinds of object occupy a similar amount of space in the visual field.
In facI, all objecls would converge toward one average size because, as I mentioned earlier, one tries to look at any thing from the distance al which it offers an image of convenient size, nol too large and nol too smaJl.
Perceived size is related rather to perceived distance. No matter how large or small the physical projection on he retina. Helmholtz maintained that the effect was brought about by what he cal1ed "unconscious judgment. The theory has been attacked on three grounds. First, Helmholtz assumed that these correclions are based mainly on knowledge previously acquired and imported into the perceptual situation by the observer.
This assumption seems to me untenable, but there is no need to argue the point here. Helmholtz has been blamed for postulating the existence of "primary" percepts which nobody has ever experi- enced. This argument has losl its force since we have come to realize how much perception takes place below the level of awareness.
The kind of reactive computation and correction, needed to straighten out the retinal distortions, is wel1 within the capacity of the nervous system and rather similar to maoy other mechanisms Ihat keep the organism goiog without conscious awareness or intervention. Helmholtz's recourse to "judgment" seemed objectionable. Was il permissible lo assume Ihat the highest mental processes are involved in elementary perception?
Actually, Helmholtz had no in- tentioo of intellectualizing perception. I nstead he believed. The properties ofany part ofthe visual field must be seen in constant relation to corresponding properties of the field as a whole.
The perceived brightness of, say, a piece of paper is derived from its place on the scale of brightness that reaches from the brightest lo the darkest value visible in the field.
Whal is being received is not an absolule but a relative value. I must repea! Quile likely il takes time lo learn to see things in relation. Whal matters is that the cognitive process which produces the so-called constancies is of a very high order of intelligence since il must evaluate any particular entity in relation to an intticate con- texto and that this feat is performed as an integral part of ongoing perception.
The accomplishment is spectacular enough whcn a given range of brightness holds good for the total field and determines the appear- ance of any objecl. Quite often. This sort of situation is brought about by uneven il lumination.
Perception has to cope here. Perceived size. The farther away an object is seen. At the same time. Ihat observersjudge sizes as though Ihe horizon were only from fifty lO three hundred feel away. But whether or nOI the out come is correct is a question Ihat does not touch the intelli- gence of the perceptuaJ performance.
Notice here also lhal as dis- lance determines size. Dislance in depth has no direct equivalent in the two-dimensional projection of Ihe retinal image. The image registers only a gradient of diminishing sizes. Such observation by indirection is an ingenious device, also used more consciously in order 10 measure the inaceessible Ihrough sorne correlated variable.
In the retina! The two components, united in the image, can be sepa- raled in perceplion because, and lo Ihe extenl to which. Only because the brightness or color values of a given context are perceived as an organized sca!
Similarly, only because an object has a grasp- able shape in itself can this shape be distinguished from the deforma- tioos that an equall y well organized system of perspective imposes upon il.
The les s c1early organized are he context and the object in themselves. In other words, perception can abstrae! I said earlier tha! Ihere are two different ways of describing the outcome of a perceptual abslraction. So far I have Ireated the so- called constaneies as though perception stripped the object of the "conlaminations" to which il is subjected by its surroundings, and showed it in isolalion. According to such a description, Ihe object is reduced lo ils invariants, the context and its effects drop out of sight, and constaney means invariabilily of appearance.
The great variety of shapes. I suggest Ihat such stability is compatible wth a much richer perceptual ex- perience than Ihal envisaged by rigid "eonstaney. First of all, the variety of object sizes is not a lawless assonment of separate tems. On the contrary. James J. Gibson has strongly emphasized this fact. What is more. Ihe projective sizes of ,,11 of its con- stituents ehange in accord. The setting as a whole is subjeeted 10 a unified and consistent modification of size.
Now it is quite true Ihat under ordinary living conditions the con textual modifications of Ihe object remain largely unobserved: ils size. This typicallack of awareness. InSlead il is. I believe. To perceive an object as immutable is lo abstract it at the highest level of generality, and that level is appropriate for all those many situations in which vision is used for the purpose of handling objects physi;:ally.
In the physi;:al world the ;:ontextual modifications observed in perception either do not exisl or do nol matter. But a person who needs the awareness of size differences-a painler. Three altitudes Experimental findings on the ";:onstandes" have nol been as dear- cut as the usual psychological trealmenl ofthe subjecI would demando The average resull for a large number of observers will indeed in- dieate a fairly high degree of constancy, bul individual reactions vary all the way from complete, or more than complete, constancy to hardly any al all.
There appear to be three altitudes. One kind of observer perceives the contribution of the contexl as an attribute of the object itself. He sees, more or less, whal a photogmphic camera records, either because he stares restrictively and unintelligently at a particular target or because he makes a deliberate effort 10 ignore the context and to concentrate on the local effect. An example is the training needed for reali stic painting. It requires Iha! Ihe student learn 10 praclice "reduction," Ihat s, 10 see a given color value as il would look through a narrow peephole.
The diffi- culties met in such training show how unnatural it is 10 see out of contexl. However, if such a reductive altitude is attained. The Impressionists Iried to replace local with context-bom color, so Ihat one and the same objecl. Under certain conditions, such reduclion 10 appearance can make identifi cation difficult. Ir 1 may use an example from a very different field of cognition: an observer watching an individual in various social situations may be unable lo grasp he character of the person as such because of hi s constantly changing behavior.
One of them, airead y mentioned, seeks to peel off the nfluence of the context in arder to obtain the local object in its pure, unimpaired state. The resultant object is constant, excepl for whatever changes it ni tia tes by itself. The observer perceives Ihe spatial location, iIJumination and so on, of Ihe objecl and uses Ihis informalion lo sublract the effect of the context from the character of the object as such.
Dynamic effect : Visual weight is always a dynamic effect, but the tension [it produces] is not necessarily oriented along a direction within the picture plane. According to the lever principle, the weight of an element increases in relation to its distance from the center. Why is that? Perhaps due to a counterbalancing effect to foreshortening. Intrinsic interest : Because of its formal complexity, intricacy, or other peculiarity, a visual area may look heavier.
Isolation : Makes for weight; e. Compactness, i. Weights attraction : Attraction exerted by the weights of neighboring elements. Structural skeleton : Directions along the axes of the structural skeleton of a shape. Subject matter : E. Movement : E. That is, weight in the upper part of perceived space counts more than in the lower part. Environmental orientation : The objective, physical vertical gravitational direction.
If we invert them, i. Even if the horizontal and vertical lines have the same length, the vertical one appears much longer see Fig.
The diagonal that runs from bottom left to top right is seen as ascending, the other as descending. Any pictorial object looks heavier at the right side of the picture. The observer subjectively identifies with the left, and whatever appears there as- sumes greater importance. Pictorial movement toward the right is perceived as being easier.
Principle 1. What is Shape? Perceptual shape may change considerably when its spatial orientation or its environment changes. Visual shapes influence one another. The shape of an object is determined not only by its boundaries; the skeleton of visual forces created by the boundaries may, in turn, influence the way boundaries are seen.
The shape of an object is depicted by the spatial features that are considered essential. Example 2. The number of angles enclosed within the figure. The number of different angles divided by the total number of angles. The number of continuous lines. Furthermore, it is not absolute simplicity that we are interested in, but relative simplicity which implies parsimony and orderliness.
Principle 2. Note that, distance in time as much the same effect as distance in space. Leveling involves a reduction of the tension inherent in the visual pattern.
Sharpening increases the ten- sion inherent in the visual pattern.
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