Visual Perception

Searching for Patterns

This discussion of visual perception is part of an introduction to media theory. The prime concern here is with how mediated our experience of the world is. The study of visual perception offers considerable evidence that the world or the image is not 'given', as people sometimes say, but constructed. In visual perception we are not like passive cameras, and even the idea that the mind takes selective 'snapshots' underplays our active interpretation of the world. These notes focus on key factors which contribute to shaping what we see.

The distinctiveness of human vision

It is worth reminding ourselves that 'the world' which we often regard as objectively 'out there' is experienced in very different ways by other creatures.

Sight dominates the way we 'see' the world. It even dominates our descriptive vocabulary. We don't know how other creatures see the world, though we do know how eyes differ in the animal kingdom amd we know that different animals vary in their reliance on vision. Of course, some creatures don't 'see' the world at all. And many creatures rely far less on vision than we do (e.g. bats, dolphins). Most mammals live in more of a world of scent than of sight. We share our reliance on sight more than scent with other primates. However, of all vertebrate animals, birds are the most dependent on sight.

Flies have what are called 'compound eyes', but it's likely to be a myth that they see multiple images. However, if we had the eyes of a fly we would see television images as separate frames, since TV images are displayed at 25 frames per second, which for the rapid scanning eye of the fly is quite slow. Although the image can be misleading, our eyes are typically described in contrast to 'compound eyes' as being 'camera-style' eyes. Animals with such

eyes comprise less than 6% of the species in the animal kingdom; more than 77% are insects and crustaceans with compound eyes.

Animals differ in visual acuity. Insects are short-sighted whereas a kestrel can spot a mouse from 1.5 km up. Hawks can spot prey 8 times further away than human beings can. The range of distances that animals can focus on is measured in dioptres. We have a good focal range (or 'accommodation') compared with most mammals. A child's range is about 14 dioptres, though an old person's is about 1 dioptre. Many creatures have poor accommodation or none. A dog copes with 1 dioptre. However, diving birds have 50 dioptres - the greatest of all animals.

Most invertebrates don't need to accommodate - sight involves short focal length and great depth of field - keeping everything in equal focus (though without much fine detail). A bee can see things from an inch or so away whereas we can't focus on things much under 6 inches away (without a magnifier). The 'f-number' of human eyes is about 2.55, whilst a standard camera lens has an f-number of 1.8. The most sensitive is a deep-sea crustacean, Gigantocypris (f-0.25), but its eyes are small, and so the quality of vision is limited.

The position of the eyes on the head also varies amongst animals. Eye position controls the extent of the field of view when the head is stationary, and also the possibility and extent of binocular vision. When the eyes are on either side of the head, the view is almost panoramic, but there is a loss of stereoscopic depth perception. Hunting animals tend to have a broader field of binocular vision. Hunted animals tend to have a far broader field of view. Hunters tend to have a much larger 'blind area' behind the head than hunted animals do. Humans have a total field of view of somewhere between 160-208 degrees, about 140 degrees or so for each eye and a binocular field of 120-180 degrees. A dog has a total field of view of about 280 degrees, 180-190 degrees for each eye and 90 degrees of binocular field. A hare has a total field of view of 360 degrees, 220 degrees for each eye, with only 30 degrees of binocular field in front and 10 degrees behind the head.

Some humans can distinguish 250 colours. Whilst some mammals are colour-blind, birds probably see more colours than we do. The desert ant has the most refined colour system amongst insects and can discriminate between colours we can't see. As we age our lenses grow more yellow and filter out some of the violet. Many insects are sensitive to ultraviolet light; vertebrates are not. We know that the colour vision of bees is different from ours, bees being highly sensitive to ultraviolet light and insensitive to red light. Many

insects, fish and birds can see beyond violet into ultraviolet radiation. Ultraviolet light gives flowers such as the yellow daisy a bright glowing core for honey-bees. At the other end of the spectrum of electromagnetic energy, some snakes are sensitive to infra-red which they use to detect the presence of warm-blooded animals. Some freshwater fish can see far further into the red or longer wavelength part of the spectrum than we can. If our eyes were as sensitive as those of goldfish we'd see the infra-red beams that control our TVs and videos. Whilst we are not sensitive to polarized light, many other animals are, and must therefore see the sky as having a far more intricate pattern than we are aware of. Of course, we can use tools to temporarily extend the visibility of the spectrum.

No creature sees fine detail in darkness, but some other creatures have far better 'night sight' than we do (e.g. foxes, cats and owls). Creatures with good night sight typically have the reflective 'eye-shine' that we often notice. It is this which allows them to make the most of whatever light there is. Owls have a sensitivity to low light intensities 50-100 times greater than that of unaided human night vision. Cats' eyes catch 50% more light than ours and are eight times more sensitive than ours at night. But such sight is typically supplemented by other senses. And even within vision, movement is the key for some creatures: the eyes of such creatures as the bee and the frog are very sensitive to movement.

Different creatures vary in the amount of the brain which is devoted to vision. Over half of the brain of the octopus and the squid is devoted to vision. But we still don't know how other creatures make sense of what their eyes detect. No single creature can see all that others can. We often forget that the human world of sight is only one such world.

Ocularcentrism

Amongst the senses, Plato gave primacy to sight. When he decided that we had five senses, Aristotle ranked sight over hearing: 'Of all the senses, trust only the sense of sight'. Plato and Aristotle closely associated vision and reason. This has been a persistent bias in Western culture. Thinking is associated with visual metaphors: 'observation' privileges visual data; phenomenon (Greek: 'exposing to sight'); definition (from definire, to draw a line around); insight, illuminate, shedding light, enlighten, vision, reflection,

clarity, survey, perspective, point of view, overview, farsighted. Other words associated with thinking also have visual roots: intelligent, idea, theory, contemplate, speculate, bright, brilliant, dull. And there is no shortage of commonly-used phrases which emphasize the primacy of the visual:

Seeing is believing Let me see, I see I'll believe it when I see it with my own eyes Seeing eye to eye It's good to see you Love at first sight What does she see in him? In the mind's eye Draw your own conclusions See what I mean?

When students in one study were asked to list the sense they'd least like to lose, 75% listed sight.

It is likely that the spread of literacy in modern times has helped to privilege sight.

Homo signifificans

I have emphasized that the world is 'seen' in different ways by different creatures, and that human beings in the modern world have come to give primacy to the visual. We do not always 'believe our own eyes' - we know that a pencil in a glass only appears to be bent, that the moon only appears to be larger when it is near the horizon and that there are such things as optical illusions.

Now I would like to emphasize that we seem as a species to be driven by a desire to make meanings: I suggest that we are, above all, Homo significans - meaning-makers. This fundamental concern underlies the process of human visual perception. Faced even by 'meaningless' patterns the mind restlessly strives to make them meaningful. Look at this image for a few moments...

It is hard not to start 'seeing things' in this abstract geometrical arrangement. The spacing is even, but we may start to see rows, or columns, or small groupings - such as of 4 black squares. We restlessly shift from one way of patterning to another - in this case none is likely to seem much more meaningful than another so we quickly tire of looking at such a frustrating image. (Yes, and you can see grey areas at the intersections - a point to which I will refer in a later lecture).

Here is another repetitive arrangement...

This time, you are more likely to impose a particular grouping on what you see. People tend to refer to five pairs of lines which are close together with fairly broad gaps between them. You are less likely to group together the lines which are further apart, perhaps partly because this would leave lonely lines on each side of the image, but also (as we will see in a later lecture) because we seem to have a predisposition to associate things which are close together.

At this stage, it is useful to note that theories about perception tend to emphasize the role of either sensory data or knowledge in the process. Some theorists adopt a data-driven or 'bottom-up' stance, according to which perception is 'direct': visual data is immediately structured in the optical array prior to any selectivity on the part of the perceiver (James J Gibson is the key proponent of 'direct perception'). Others (e.g. Richard L Gregory) adopt a

'constructivist' or 'top-down' stance emphasizing the importance of prior knowledge and hypotheses. Both processes are important: if we were purely data-driven we would be mindless automatons; if we were purely theory-driven we would be disembodied dreamers.

We have all heard of the psychoanalyst's 'Rorshach Inkblots'. These were of course intended to be very much open to interpretation. The idea was that what people reported seeing in these images involved some projection of their own deep concerns. Here is one such blot...

We all seem to 'see things' in inkblots, flames, stains, clouds and so on. Some of us may, of course, be more 'suggestible' than others...

Hamlet: Do you see yonder cloud that’s almost in shape of a camel?Polonius: By the Mass, and ‘tis like a camel indeed.Hamlet: Methinks it is like a weasel.Polonius: It is backed like a weasel.Hamlet: Or like a whale?Polonius: Very like a whale.

Hamlet (Act II, Scene II)

Some images are more open to interpretation than others. Most of us would see no 'intended reading' in such natural phenomena as flames and clouds (though this wouldn't stop us seeing meaningful patterns in them). We would generally accept that there is typically less openness to interpretation when it comes to images deliberately designed by human beings. The declaration that a road sign is 'open to interpretation' is not likely to be much of a defence for ignoring its intended meaning in the eyes of the law! On the other hand, we would usually feel free to be fairly free-ranging in our interpretation of an image which we knew to be intended as a work of art.

Here is another black and white image. For some people it will be immediately obvious - others may not instantly recognize it.

Familiar as this image is, whilst we may recognize it as a map, we may not immediately recognize it as representing the world (upside down, according to the way we're used to seeing it). However, once we 'know what to look for', we have no difficulty seeing it as a map of the world which happens to be upside down.

The illustration below is well-known from psychology textbooks, so most students will already know what to look for in it.

Those who haven't seen it before shouldn't have too much difficulty if they are told that there is a dalmation dog nosing around on a path near a tree. The dog is in the centre of the picture, facing the top-left corner. Often, significant details seem to suddenly lead to the 'click' of recognition, at which point it is hard to understand why we hadn't seen the 'hidden' image in the first place.

On subsequent occasions we see the image without any of our initial difficulty.

Sometimes images are neither open to almost any interpretation nor constrained to a single 'preferred interpretation'. Some of the images used in the study of visual perception have been carefully designed to be interpreted in two different but specific ways. Look at the following example, for instance.

At first sight, this may seem to be either a seal or a donkey (alternatives which we would be unlikely to confuse in real life). Here, you will initially see either a seal or a donkey, but not both at once. You bring your own preferred interpretation to the image - a phenomenon known to psychologists as perceptual set (this will be discussed in a later lecture). In cases where one alternative interpretation repeatedly elicits far more support than the other, it might be said that the image itself has a preferred interpretation (though this might be culturally-specific).

Here is another example, though this may be more well-known from psychology textbooks...

Here the intended alternatives are a duck and a hare. What do you see first? Such examples demonstrate that your own preferred interpretation is part of

what you bring to making sense of an image. In the context of media theory, the relative openness of images to interpretation can serve as a reminder that the 'meaning' of an image cannot be simply equated with a universal, unitary, fixed and objective 'content' - meaning is not 'extracted' but is constructed in the process of interpretation. But such constructed meanings are not unconstrained: if you reported in all seriousness that your interpretation of the image shown above was an elephant, you would be in danger of being regarded as either mentally deficient or insane.

Selectivity and Perceptual Constancy

Categorization is a key 'top-down' process which is involved in perception. Categories simplify. Categorization has a number of functions:

it makes complexity manageable; it speeds up recognition; it reduces effort and learning; it makes the most of past experience; it enables the inferences about further attributes (going beyond what is 'given'); it makes events predictable; it supports systematization; it bonds social behaviour (providing shared frameworks); it tailors the world to our purposes; it makes the world seem more meaningful.

The cost of these advantages is a loss of particularity and uniqueness in perception and recall. For Romantics, it is also regarded as inducing a sense of distance from the world. The way we categorize phenomena seems to be a 'natural' 'reflection of reality', leading us to forget the role of categorization in constructing the world.

Probably the most well-known example of the cultural diversity of categories is that Eskimos have dozens of words for 'snow' - an assertion which is frequently attributed to Benjamin Lee Whorf. Actually, Whorf seems never to have claimed that Eskimos had more than five words for snow (Whorf 1956, 216). However, a more recent study - not of the Inuit but of the Koyukon Indians of the subarctic forest - does list 16 terms for snow, representing these distinctions:

snow deep snow falling snow blowing snow snow on the ground granular snow beneath the surface hard drifted snow snow thawed previously and then frozen earliest crusted snow in spring thinly crusted snow snow drifted over a steep bank, making it steeper snow cornice on a mountain heavy drifting snow slushy snow on the ground snow caught on tree branches fluffy or powder snow (Nelson 1983, 262-3)

I do not intend to discuss the controversial issue of the extent to which the way we perceive the world may be influenced by the categories which are embedded in the language available to us. I have discussed the so-called Sapir-Whorf hypothesis elsewhere. Suffice it to say that words can be found in English, as above, to refer to distinctions which we may not habitually make, but that this does not rule out the possibility that the categories which we employ may not only reflect our view of the world but may also sometimes exercise subtle influences upon it.

There is research evidence that verbal labels may influence the recall of visual images. In a well-known experiment by Carmichael, Hogan and Walter (1932), observers were shown simple line drawings each of which was associated with either of two verbal captions - e.g. a drawing of two circles linked by a straight line bore either the caption 'eye-glasses' or the caption 'dumb-bells'. The observers were then asked to reproduce the drawings. Their reproductions showed a strong tendency to distort the original image to make it closer to the verbal label which had been attached to it.

The Stroop Colour-Word Test can be used to illustrate the difficulties which we can experience in separating labels from what they refer to (see below). Try counting the number of green words, for instance.

red green blue green red yellow blueyellow red blue yellow green red blueblue yellow yellow blue red blue yellow

red green green red green green greengreen blue blue yellow yellow yellowyellow red green yellow blue green redblue green red red green red green bluered yellow yellow red blue yellow blueyellow blue red blue green green yellowgreen red yellow blue yellow blue redblue red blue green red yellow bluegreen green red yellow blue yellow blue

A well-known study demonstrating the influence of language on recall is that of Elizabeth Loftus (1974 & 1979). She showed observers a short film of a traffic accident and asked how fast the cars had been going. However, the wording of the question differed between the two groups asked. Those in one group were asked 'About how fast were the cars going when they hit each other?' whilst those in the second group were asked 'About how fast were the cars going when they smashed into each other?' Those who had been asked the question with the term smashed gave higher estimates of the cars' speeds than the others did. A week later, the same observers were asked whether they had seen any broken glass (there had been none). More than twice as many of those questioned with the word 'smashed' reported seeing the nonexistent glass as those questioned with the word 'hit'.

It is not only with respect to categorization thay perception is described as 'selective'. Recovering his sight after 30 years of blindness, one man reported:

When I could see again, objects literally hurled themselves at me. One of the things a normal person knows from long habit is what not to look at. Things that don't matter, or that confuse, are simply shut out of their seeing minds. I had forgotten this, and tried to see everything at once; consequently I saw almost nothing. (Muenzinger 1942)

Perception is unavoidably selective: we can't see all there is to see. There are of course physiological limits (both for the human species and for individuals); some argue that there are limits to cognitive capacity. And then there are the constraints of our locational viewpoint: we can't see things from every angle at once. But in addition to such physical limits we focus on salient features and ignore details which are irrelevant to our current purposes or interests. Selectivity thus involves omission. Some commentators use the 'filter' metaphor - we 'filter out' data, but this suggests a certain passivity: we may also 'seek out' data of a certain kind.

Selective attention is assisted by redundancy: we don't always need much data in order to recognize something. Often we can manage with minimal visual data, making use of what is called 'redundancy'. You may know those 'blocky' pictures of famous people in which you can just about recognize who it is. Our schemata allow us to 'fill in gaps' because we know what should be there. So selectivity also involves addition.

Selectivity also involves organization: foregrounding, backgrounding and rearranging features. Objects, events or situations are 'sized up' in relation to our frames of reference, and these influence how perception is structured (Newcomb 1952, 88-96).

Gordon Allport and Leo Postman (1945; Newcomb 1952, 88-96) offered a classic account of the selectivity of perception in their study of rumour. Whenever an event is open to divergent interpretations, reporting it involves transforming it. The selection, retention, reporting and retelling of events routinely involves several kinds of transformations. All of these involve simplifying events to make them more meaningful in terms of personal interests, needs and experience. The process is exaggerated where memory and retelling are involved, but it is already at work in the selectivity involved in the initial perception of an event.

Contrary to the popular idea that rumours ‘snowball’, becoming more elaborate in the telling, psychological studies suggest that retelling tends to make accounts shorter, more concise, more easily grasped and told. There is an increasing tendency to use fewer words. Levelling is the selective process by which certain details are omitted. However, items of particular interest to the reporters, which confirm their expectations or help to structure their reports, do tend to persist.

Sharpening is the reciprocal selective process of levelling. Alongside the loss of some details, there also tends to be a pointing-up of a limited number of details which caught the individual’s attention, often including attention-grabbing words. Temporal sharpening involves a tendency to describe events in the present tense. Movement is often emphasized or introduced. Items prominent because of their relative size or quantity tend to be retained. Labels tend to persist. Primacy effects may lead to the retention of items coming first in a series. Familiar symbols are also likely to be retained. Explanations may be introduced, especially to produce ‘closure’.

Underlying the selective processes of levelling and sharpening, and of transpositions, importations and other transformations involved in retellings,

Allport and Postman (1945) argue, is the process of assimilation. This involves the influence of habits, interests and sentiments on reporters and listeners. Aspects of a story are sharpened or levelled to make them more consistent with what is seen as the principal theme of the story, thus making the story more coherent and ‘well-rounded’. Items relevant to the theme may be imported and those irrelevant to the theme may be omitted. Apparent ‘gaps’ may be filled. And some details may be changed to make them more consistent.

Assimilation by condensation involves fusing several details into one. Assimilation to expectation involves transforming details into what one’s habits of thought suggest they usually are.

Assimilation to linguistic habits involves fitting phenomena into the familiar frameworks of conventional verbal categories.

Assimilation to interest involves retellings from the perspective of the particular occupational interests or roles of the teller (especially where these interests are shared with listeners), giving primary attention to details which reflect such interests.

Assimilation to prejudice may simply involve assimilation to expectation or to linguistic categories, but it may also involve deep emotional assimilation to hostility based on racial, class or personal prejudices.

Selective perception is based on what seems to 'stand out'. Much of this 'standing out' is related to our purposes, interests, expectations, past experiences and the current demands of the situation. However, some seems more widely-shared - throughout a culture or even across the human species. For instance, we seem to have a general preference for features which are large and/or bright and/or moving, for the novel, the surprising and the incongruous, and for what is meaningfully complex ('looking like things'), and our fixation tends to be on discontinuities, corners and contours. We will turn to such apparently universal features of human perception in discussing Gestalt theories.

Some aspects of perception can be usefully discussed in terms of 'selectivity', but to see perception purely in terms of selectivity would be reductive. It would court the danger of implying that perception is relatively passive and would downplay the active construction of reality.

This is related to what psychologists refer to as perceptual constancy. Our perception of objects is far more constant or stable than our retinal images. Retinal images change with the movement of the eyes, the head and our position, together with changing light. If we relied only on retinal images for visual perception we would always be conscious of people growing physically bigger when they came closer, objects changing their shapes whenever we moved, and colours changing with every shift in lighting conditions. Counteracting the chaos of constant change in retinal images, the visual properties of objects tend to remain constant in consciousness. We are not usually conscious of people appearing to get bigger as they approach us or of things appearing to change shape according to the angles from which we view them. In relation to visual perception, key 'constancies' are: size, shape, lightness and colour.

The following illustration demonstrates how a door appears to change shape as it is opened. Shape constancy ensures that we are not typically conscious of this.

With regard to shape constancy, R H Thouless published a paper entitled 'Phenomenal regression to the "real" object' in the British Journal of Psychology in 1931. He reported an experiment in which he exposed a circular disc at various angles and asked observers to judge its shape each time. The observers did so by selecting a matching disc from a series of circular and elliptical ones which they had been given. When the disc was directly in front of them and in a vertical plane the judgement was easy, of course. But when Thouless rotated the disc away from the observer so that it appeared elliptical, the task was more difficult. Judgements of shape reflected a compromise between the shape as displayed at an angle (an ellipse) and the actual shape of the object (the circle). Observers did not see the shape as it would be on the retina but instead exhibited a 'phenomenal regression' - the phenomenal or apparent shape was inbetween the tilted shape and the vertical shape. This has been called a 'perceptual compromise'.

Familiarity of shape is also an explanation of the illusion generated by a special 'room' called 'the Ames Room' (students in Wales: note that there is an Ames Room at Techniquest in Cardiff). Observers peer through a single hole in a wall of this structure (thus having only monocular cues to depth, as in looking at a photograph or painting, rather than a space around which one could move). Two people of similar size within this special room would look very different in size to observers as indicated in the following illustration.

The reason for this strange illusion is to do with the extraordinary construction of the room, the lefthand wall of which actually goes far further back than the righthand wall, for instance. We are so used to rooms being rectangular that we intepret everything within it on this assumption. The Ames Room represents the mind making a habitual bet, and only getting it wrong because of a careful conspiracy.

Context and Expectations

Someone once said that there is no meaning without context. Various kinds of context are important in shaping our interpretation of what we see. As a reminder of the importance of making clear what is meant by the importance of 'context' in perception I briefly list here several very different uses of the term. However, I would not suggest that in practice tidy distinctions can always be usefully made.

The largest frame is that of the historical context of perception. Some theorists, such as Marshall McLuhan (1962), Walter Ong (1967) and Donald Lowe (1982), have argued that there have been shifts over time in the human 'sensorium' - that is, in the 'balance' of our senses or the priority which we give to some compared with others. Such argue that in western urban cultures we have come to rely more on sight than on any other sense (this was referred to in Visual Perception 1 as 'ocularcentrism').

Another major framework is that of the socio-cultural context of perception. Just as there may be subtle differences in human perception over time there may also be differences attributable to culture. Some of these were alluded to in Visual Perception 3. Constance Classen (1993) in her book Worlds of Sense shows that different cultures accord priority to different senses - the Ongee of the Andaman Islands, for instance, live in a world ordered by smell.

A native American Indian writer called Jamake Highwater, who is of Blackfeet/Cherokee heritage, draws attention in the following extract to radically different ways of seeing the world:

Evidence that Indians have a different manner of looking at the world can be found in the contrast between the ways in which Indian and non-Indian artists depict the same events. That difference is not necessarily a matter of 'error' or simply a variation in imagery. It represents an entirely individual way of seeing the world. For instance, in a sixteenth-century anonymous engraving of a famous scene from the white man's history an artist depicted a sailing vessel anchored offshore with a landing party of elegantly dressed gentlemen disembarking while regal, Europeanized Indians look on - one carrying a 'peace pipe' expressly for this festive occasion.

The drawing by an Indian, on the other hand, records a totally different scene: Indians gasping in amazement as a floating island, covered with tall defoliated trees and odd creatures with hairy faces, approaches.

When I showed the two pictures to white people they said in effect: 'Well, of course you realize that what those Indians thought they saw was not really there. They were unfamiliar with what was happening to them and so they misunderstood their experience.' In other words, there were no defoliated trees, no floating island, but a ship with a party of explorers.

Indians, looking at the same pictures, pause with perplexity, and then say, 'Well, after all, a ship is a floating island, and what really are the masts of a ship but the trunks of tall trees?' In other words, what the Indians saw was real in terms of their own experience.

The Indians saw a floating island while white people saw a ship. Isn't it also possible - if we use the bounds of twentieth-century imagination – that

another, more alien people with an entirely different way of seeing and thinking might see neither an island or a ship? They might for example see the complex networks of molecules that physics tells us produce the outward shapes, colours and textures that we simply see as objects. Albert Einstein showed us that objects, as well as scientific observation of them, are not experienced directly, and that common- sense thinking is a kind of shorthand that attempts to convert the fluid, sensuous animation and immediacy of the world into illusory constructs such as stones, trees, ships and stars.

We see the world in terms of our cultural heritage and the capacity of our perceptual organs to deliver culturally predetermined messages to us. (Highwater 1981, 6-8)

Both the historical and socio-cultural context of perception are vast themes which will not be explored further here, but such studies do help to emphasize that 'the world' is not simply indisputably 'out there' but is to some extent constructed in the process of perception. Within a given socio-cultural context, there are widely-shared interpretive conventions and practices. Whilst the basic processes of human perception are largely universal there is scope for subtle but significant variations over space and time.

Several other kinds of context are commonly referred to. I have referred already, in Visual Perception 3, to the importance of individual factors which can have an influence on perception. An emphasis on the individual as a context emphasizes the role of the various long-term characteristics of individual perceivers such as values, attitudes, habits and so on. An emphasis on the situational context considers such transitory situational factors as goals, intentions, situational constraints and contextual expectancies. Finally, an emphasis on the structural context stresses structural features and relationships (such as the relationship between one line and another) 'in' what is perceived - though the extent to which there is agreement about even such low-level formal features may vary.

Five main definitions of the scope of the term 'context' have been listed here in relation to their potential influence on perception:

historical socio-cultural individual situational

structural

Whilst it may be useful to be alert to the very different meanings that the word 'context' can have, disentangling them is problematic.

A very well-known study by Bugelski and Alampay (1961) can be seen as showing the importance of situational context. Their experiment is often used as an example of the influence of what psychologists call 'perceptual set': a predisposition to perceive something in relation to prior perceptual experiences. Perceptual set is broader than situational context, since it may involve either long-term (for instance, cultural) prior experience or, as in this case, short-term or situational factors (Murch 1973, 300-301). Groups of observers in the experiment were shown an ambiguous line drawing which was designed to be open to interpretation either as a rat or as a bald man wearing spectacles. Prior to seeing this image, two groups were shown from one to four drawings in a similar style. One group was shown drawings of various animals and the second group was shown drawings of human faces (see illustration below). A control group was shown no pictures beforehand. 81% of the control group reported seeing the ambiguous image as a man rather than a rat. The more pictures of animals that the 'animal' group had seen, the more likely they were to see a rat rather than a man (with 4 prior images of animals 100% then saw a rat). From 73-80% of the 'faces' group subsequently saw a man rather than a rat.

The influence of perceptual set has also been explored in relation to the famous image shown below:

This image was designed to be interpreted as either a young woman or an old woman. It was introduced into the psychological literature by Edwin G Boring (1930) (though it was published by the British cartoonist W E Hill in 1915, and is thought to be based on a French version of 15 years earlier). It is sometimes given the chauvinistic label of 'The Wife and the Mother-in-Law'. In order to study the role of perceptual set Robert Leeper (1935) had the image redrawn in two 'biased' forms: one which emphasized the old woman and the other which emphasized the young woman (see image below).

Leeper varied the conditions of viewing for five groups. A control group was shown only the ambiguous drawing, and 65% of this group spontaneously described the image as that of a young woman. The second and third groups were first given a verbal description of the old woman and the young woman respectively. The fourth and fifth groups were first shown the 'old' version and the 'young' version respectively. Groups 2 to 5 were then shown the original ambiguous image. Leeper found that each of the primed groups was 'locked-in' to their previous interpretation. 100% of group 5, which had seen the young version first, interpreted the ambiguous image as a young woman. 94% of group 4, which had seen the old version first, reported seeing the old woman in the ambiguous image. The percentages opting for each interpretation amongst those given verbal descriptions were much the same as for the control group. Gerald Murch (1973, 305) was unable to replicate these findings (94% of his control group first saw the young woman) and suggested

that the image was by then so well-known that this may have influenced the results.

Particular situational contexts set up expectations in the observer. Bruner and Postman (1949) conducted an experiment in which playing-cards were used, some of which had the colour changed from red to black or vice versa. The cards were exposed in succession for a very short time. Subjects identified them as follows:

some normalized the colours of the anomalous cards; some normalized the suits to make them compatible with the anomalous colours; some compromised and saw the anomalous cards as brown or purple.

Interpretation here was dominated by what the situational context suggested that people ought to be seeing. A shorter time of exposure was necessary for people to name the normal cards than the anomalous ones.

In one experiment, Steven Palmer (1975) first presented a situational context such as a kitchen scene and then briefly flashed on a target image. When asked to identify a loaf-like image, people who had first seen the kitchen correctly identified it as a loaf 80% of the time. Obviously, a loaf of bread is the kind of thing you’d expect to find in a kitchen. They were asked to identify an image like an open US mailbox and an image resembling a drum - two objects not usually associated with the kitchen. The images were a little ambiguous: the mailbox was a little like the shape of a loaf with a slice of bread lying next to it, and the drum could have been interpreted as the lid of a jar. People who had first seen the kitchen only identified these as a mailbox and a drum 40% of the time. The ability to identify objects was affected by people’s expectations concerning what is likely to be found in a kitchen.

I have mentioned that situational contexts generate certain (short-term) expectations but it is worth noting in passing that expectations may also be set up by longer-term influences - such as by stereotypes, prejudices and past experience.

To return to contexts, here is an example of structural context. This pattern of circles is known as the Ebbinghaus (or Titchener) illusion. It is an illusion of relative size (or more strictly, area). Here the formal relationship between the parts of the image leads the small white circle (which is the same size in both images) to seem larger in the structural context of the tiny black circles than amongst the large black circles. There is no shortage of examples of the role of structural context amongst the geometrical illusions which can be found in psychology textbooks so no further examples of the role of structural context will be discussed here.

At this point it is useful to introduce schema theory briefly. A schema (plural 'schemata' or 'schemas') is a kind of mental template or framework which we use to make sense of things. Particular circumstances seem to activate appropriate schemata, which set up various standard expectations about such contexts. Such schemata develop from experience. They help us to ‘go beyond the information given’ (as Jerome Bruner famously put it) by making assumptions about what is usual in similar contexts. They allow us, for instance, to make inferences about things which are not currently directly visible. The application of schemata and the expectations which they set up represents 'top-down' processes in perception (whilst the activation of schemata by sensory data is a 'bottom-up' process). A good example of the role of top-down processes is where you think that you recognize someone in the street and then realize (from sensory data) that you are wrong. We are often misled in this way by situational contexts, by wishful thinking and so on, ignoring contradictory sensory data in favour of our expectations.

In an experiment by Brewer and Treyens (1981), individual participants were asked to wait in an office. The experimenter said that this was his office and that they should wait there whilst he checked the laboratory to see if the previous participant had finished. After 35 seconds, he returned and took the participant to another room where they were asked to recall everything in the room in which they had been waiting. People showed a strong tendency to recall objects consistent with the typical ‘office schema’. Nearly everyone remembered the desk and the chair next to it. Only eight out of the 30 recalled the skull (!), few recalled the wine bottle or the coffee pot, and only one recalled the picnic basket. Some recalled items that had not been there at all: 9 remembered books. This shows how people may introduce new items consistent with the schema.

In an experiment by Baggett (1975) participants were shown a series of simple line drawings telling a story. One story showed a long-haired man

entering a barbershop, then sitting in the barber’s chair, and finally leaving the shop with shorter hair. In a later test they also saw a picture showing the actual haircut, which had not been present originally. People were fairly good at remembering that this picture had not been present if the test followed immediately after the initial showing. However, if the test occurred a week after the initial presentation most people claimed that they had seen the haircutting picture in the original sequence. This shows the way in which we incorporate in our memories inferences derived from our schemata. This experiment was concerned with memory rather than perception, but it is difficult to separate these processes if you take the stance that no perception is 'immediate'.

References and Suggested Reading

Anderson, Joseph and Barbara Fisher. "The Myth of Persistence of Vision Revisited," Journal of Film and Video, Vol. 45, No. 1 (Spring 1993): 3-12. URL Bazin, André (1967), What is Cinema?, Vol. I, Translation. Hugh Gray, Berkeley: University of California Press

Cook, David A. (1981), A History of Narrative Film, New York, W. W. Norton & Company

Haber, Ralph Norman and Maurice Hershenson (1980), The Psychology of Visual Perception (second edition), London: Holt, Rinehart and Winston.

Kline, K. AO Holcombe, DM Eagleman - (2004) "Illusory motion is caused by rivalry, not by perceptual snapshots of the visual field" Vision Research 44, URL http://nba.uth.tmc.edu/homepage/eagleman/papers/KlineHolcombeEaglemanVisRes2004.pdf

Koningsberg, Ira (1997), The Complete Film Dictionary (Second Edition), London: Bloomsbury.

Metz, Christian (1991), Film Language : A Semiotics of The Cinema, translated by Michael Taylor, Chicago: University of Chicago Press.

TABLE OF CONTENTS

Searching for Patterns

The distinctiveness of human vision

Ocularcentrism

Homo significance

Selectivity and Perceptual Constancy

Context and Expectations

References

Organizations run due to the attitudes and behavior of the employees. Whatever the action comes that brings an output may positive or negative depends upon the commitment or negligence of the employees that is mainly based on his or her behavior towards the job and team members.

Therefore, the importance of Organizational behavior can not be denied. The study of the subject gives a complete picture of the respond ness of the subordinates to the managers so that they may take right decisions at the right time.

In this regards an assignment has been successfully accomplished by our group members. We our work would be appreciated.

Our group is very obliged and thankful to SIR.MUHAMMAD ZUBAIR KHAN for his congenial support and guidance that enabled us to prepare an assignment about the Visual Perception.

PREFACE

We tried our level best to thoroughly overlook the topic in a quite comprehensive way.

Thank You, Sir & May God Bless You.

M.RIAZ KHAN

Organizational Theory & Behavior

His Excellency:

SIR. MUHAMMAD ZUBAIR KHAN

By: MUHAMMAD RIAZ KHAN ( MBA 2nd Term)