Introduction Click here
History of understanding visual perception Click here
Visual perception mechanisms and models Click here
Environmental psychological approaches to perception Click here
Conclusions Click here
References Click here
Psychology is the science of the mind and its functions, especially in relation to behavior. It covers human senses, perceptions, emotions, cognition and action and is based on empirical, objectively derived and verifiable evidence from observation, testing and evaluation of the human condition.
Arising out of natural philosophy in the late nineteenth century, it focused initially on the faculties of the mind and sought to understand how the physiological processes of the senses were translated by the brain into sensations and perceptions.
During the nineteenth century, experimental psychology began the study of how sensory experience is dependent on stimulation of the sense organs (Boring, 1990). Psychophysics is the link between physiology and psychology and has been of considerable importance in the contemporary studies of aesthetics.
In the early twentieth century in Germany, Gestalt theory developed to cover the psychology of perception. It built on the concept that the whole is more than the sum of the parts; actually, Gestalt postulated that the whole is different than the sum of the parts. This is a highly relevant concept for landscape quality where aesthetic delight derives from the whole landscape.
In the latter decades of the twentieth century, increasing numbers of psychologists reflected the growing community concern for the environment and expanded environmental psychology into new areas of research such as environmental attitudes, aesthetics, urban design, crowding, environmental stress, restorative influence of nature, coping with natural disaster management, environmental cognition and mental maps.
This theme examines various human world views which form the basis of perception. An historical briefing is followed by a review of visual perception mechanisms and models and a summary of environmental psychological approaches to perception. The contemporary contributions made by environmental psychology to perception and the relevance to landscape of the perception theories are reviewed.
HISTORY OF UNDERSTANDING VISUAL PERCEPTION
Plato, Aristotle and Euclid
Plato believed that the eye projected a fiery emanation outwards to objects in view where this fire coalesced with the object, and sensations were thus conveyed to the mind (Uttal, 1983). Aristotle roundly rejected Plato’s emanation model, instead arguing that vision resulted from an emanation from the object being transmitted to the eye where it was absorbed. Plato’s emanation theory blocked progress in the understanding of perception until about 1,000 AD when discoveries of the physics of light shifted the focus to the Aristotelian theory. Parallels can be drawn between these theories with the philosophy of beauty, contrasting beauty being an objective physical quality (cf Plato’s fiery emanation) versus beauty being in the eye of the beholder (cf Aristotle’s absorption by the eye).
The mathematician, Euclid, established seven postulates which provide the basis of geometrical optics and form perception. One of these is the law of visual angle or retinal size: The things seen under a larger angle appear larger, those under a smaller angle appear smaller, and those under equal angle appear equal. (Uttal, 1983).
The influence of anatomical studies by Arab scholars together with increasing interest in Euclidean geometrical and perception models led to the flourishing of scientific and artistic endeavors during the Renaissance. Perspective in painting was understood for the first time. Kepler (1571 – 1630) solved the problems of optics as applied to the retinal image and permanently laid Plato’s emanation theory to rest. Rene Descartes (1596 – 1650) dissected an ox’s eye and detected an image upon the retina when light was passed through the lens. Rather than simply regarding sight as the imprint of the physical image upon the retina, Descartes realized that it is the result of brain activity, an intellectual leap that parallels the contemporary subjective view of aesthetics. He even proposed that some form of coding of the visual image occurred prior to its interpretation by the brain.
The British empiricist philosophers, including Locke, Berkeley and Hume, addressed visual perception as a key question of philosophical inquiry. In his famous book Essay Towards a New Theory of Vision (1709), Berkeley argued that as vision provides only two-dimensional images, it is inadequate for correctly perceiving the world and that the process of association is necessary. He differentiated between mediate visual stimuli which included depth perception, and immediate or innate stimuli, such as width or color. Perception of mediate stimuli required indirect evaluation, while immediate stimuli could be perceived directly. Berkeley also believed that mediated precepts involve learning; for example, depth perception requires tactile experience.
Both Descartes and Kant disputed the empiricist’s view that the mind was a tabula rasa (blank slate), Descartes arguing that it possessed innate ideas about form, size and other properties of objects, while Kant believed the mind imposed its own internal conception of space and time upon the sensory information it receives (Rock, 1984). The Gestaltists were the direct heirs of this approach. They argued that, although our senses perceive chaotic messages, there is a process of perceptual organization in the mind that brings order out of this chaos to organize them into distinct and segregated units such as objects with specific shapes separated from a background.
Knowledge of the anatomy and physiology of the brain increased during the eighteenth century. The theory of Johannes Muller (1801 – 1858) that sensations or signals encode the shape and quality of stimuli and passed from the retina to the brain transformed the debate from philosophy to science. He defined ten laws of the sensory process which can be summarized as three main generalisations (O’Neil, 1977):
- Regardless of how a sense-receptor is activated – whether by light, sound, chemical substances, mechanical pressures or electrical stimuli – it will yield, if an experience results, a given type of ‘secondary’ quality;
- All that we are directly aware of in sensation is the state of the sensory nerve – the neurophysiological effect;
- Although sensations are subjective in that they are received by the senses, they seem objective.
Muller’s laws dominated early experimental sensory psychology in the nineteenth century. Vision was regarded as a process within the brain and was analyzed in terms of neural networks.
In the nineteenth century, psychology sought to pattern itself on the physical sciences and hypothesized that there was a one-to-one correlation between experience of the external world and the stimulation of the mind. This was the constancy hypothesis – that given a particular stimulus, the same response will occur independent of other conditions (Wolman (a), 1973). It parallels the principle of uniformitarianism in the earth sciences, that the physical processes occurring today are identical to those that occurred in past ages. During the nineteenth century, the empirical approach dominated, based on analysis of observable events and processes, resulting in attempts to understand the components of perception through an introspective method.
In the second half of the nineteenth century, Hermann von Helmholtz (1821 – 1894) undertook extensive research on sensory processes, perception and physiological optics. He believed that experience provides us with the understanding of objects from which we infer their nature and described this unconscious inference: The sensations of the senses are tokens for our unconscious, it being left to our intelligence to learn how to comprehend their meaning (Rock, 1984).
The science of psychophysics originated in 1860 when the German physicist, Gustav Fechner (1801 – 1887) published Elemente der Psychophysik in Leipzig. Psychophysics is the science of the measuring the influence of the information received by the senses (sight, sound, taste, smell and touch) on the brain, connecting the publicly observable world and a person’s privately experienced impression of it (Wikipedia, 2013). Building on previous work by Ernst Weber, his major contribution was the Weber-Fechner scale which quantified the relationship between a sensation and the stimulus it provides to the brain; as the intensity of the sensation increased arithmetically, the stimulus increased geometrically: S = K log I (i.e. Sensation S = Constant K multiplied by the logarithm of the Intensity I). Together with William Wundt (1832 – 1920) and Hermann von Helmholtz he established the scientific basis of psychology, overturning beliefs by Kant and others that it was impossible to quantify psychology.
Psychophysics of space perception is based on seeking correlations between the information received through retinal projection and perception of the environment. This involves exhaustive research of the stimuli. James Gibson, the foremost contemporary advocate of this view, rejects the approach based upon the processing of individual chunks of information and postulates that information is viewed holistically as meaningful entities, paralleling the Gestaltists, who worked on the total image.
Atomistic (or structuralist) psychology taught that:
“all psychological facts (not only those in perception) consist of unrelated inert atoms and that almost the only factors that combine these atoms and thus introduce action are associations formed under the influence of mere contiguity” (Kohler, 1959).
This approach used analytic introspection to relate the association of experience to the stimulus energies they provoked. However, the atomistic approach could not explain depth and shape; neither could it explain significant changes to a scene that result from changes in its parts.
Gestalt psychology developed from the realization in the late nineteenth century that the atomistic approach to psychology and perception which reduced phenomena to their smallest possible quanta failed to explain characteristics that could derive from the individual parts. This approach assumed that sense data comprised pointillist mosaic of bits and pieces that were then aggregated into larger entities (Ehrenzweig, 1967). A similar atomistic approach characterizes many contemporary landscape analyzes, e.g. Shafer et al, 1969, Daniel & Boster 1976, Dearden 1980. Typically these divide a landscape into its constituent parts, assess responses to the parts and then recombine them.
In 1890, Christian von Ehrenfels identified the form quality or Gestaltqualitat as a key aspect of features. Form qualities are properties of a whole or an entity which does not reside in its constituent parts (Wolman (a), 1973). A square is more than the sum total of four equal lines and four right angles; its most important characteristic is its squareness. A melody is not just a collection of notes but a set of certain notes in a particular order and style. If the relationship between the notes changes, so too does the tune, but significantly the melody is retained if it is transposed into another key. Similarly, a square shape retains its essential form regardless of size. Fractals have the same property of being an identical form at varying scales. An idea can be expressed in different languages but remain identifiable.
Thus the Gestaltqualitat is retained provided the relations between the elements remain unchanged. Transferability does not depend on having common elements, as under the atomistic approach, but rather they have similar formal or structural properties. Relationships of elements and transposability are key properties of form qualities. Von Ehrenfels advocated the inclusion of form qualities along with sensations to understand the perception of forms, music and movement.
In 1900, Friedrich Schumann demonstrated the subtlety of form qualities; for example, he showed that rotating a square through 45º produces a diamond, still a square but, in contrast to the stable and substantial square, a rather unstable delicate form.
Abandonment of the constancy hypothesis followed research by Max Wertheimer (1880 – 1943) at the University of Frankfurt and later together with Wolfgang Kohler (1887 – 1967) and Kurt Koffka (1886 – 1941). All three rejected the atomistic approach.
In 1912, Wertheimer published the paper that gave birth to the Gestalt movement. It was a paper on the phi phenomenon – the projection of two slightly separated spots of light in succession on a screen to give the impression of a single spot of light moving across the screen. Although the individual images remain stationary, there is an “apparent movement” that does not derive from a series of sensations but is a new outcome from the effect of two stimulus events working in cooperation. The effect is similar to that of motion pictures where the viewer actually sees a series of discrete images. Wertheimer deduced that the apparent movement was the result of a sequence of successive images and that this occurred outside the perceptual field.
In the German, “Gestalt” has two meanings (Kohler, 1947):
- It connotes a shape or form as an attribute of things;
- It has the meaning of a concrete entity per se, that has, or may have a shape as one of its characteristics.
Kohler recognised, however, that the use of the term has extended well beyond the content of shape, such as learning, recall, thinking, acting, and biology.
Wertheimer’s definition of Gestalt is broader and allows for its wider use:
In contrast to the atomists, the Gestaltists made organization the key. They examined the organization of whole objects – music, forms, faces – concentrating on mental processes as being dynamic, structural units rather than bundles of sensations linked by association or imagination. The Gestaltists likened the atomistic model to a telegraph exchange, and their own model as the distribution of stresses on soap bubbles (Hochberg, 1974); the atomistic object containing myriads of operations each operating independently without affecting others, the Gestalt object comprising a form dependent totally on the contribution of each element to the whole.
Wertheimer, Kohler, Koffka and other Gestalt psychologists extended the approach to other areas of perception: problem solving, learning and thinking. Kurt Lewin applied it to social psychology, motivation and personality, Kohler to animal behavior, while others applied it to economic behavior and aesthetics. Rudolf Arnheim (1974) who was prominent in art and aesthetics considered that the foundations of our present knowledge of visual perception were laid down in the laboratories of the Gestalt psychologists.
The Gestalt approach of holistic perceptual processing, as distinct from an elementalistic approach, has gained support over recent decades. Nevertheless, the dominant theories of form perception have tended to be elementalistic and neuro-reductionist in concept and language (Bruce & Green, 1990).
Gestalt and its relevance to aesthetics is examined in more detail here.
Early in the twentieth century, J. B. Watson developed behavioral psychology which replaced introspective terms such as sensations and perceptions with objectively observable discriminative responses (Bruce & Green, 1990). The behavioral approach focused on observation of behavior rather than understanding internal processes. Contemporary psychology is still dominantly behavioral in orientation, although verbal explanations of subjects’ experiences are regarded as legitimate.
Whilst behaviorism developed in the United States of America, the Gestalt psychologists in Europe developed the phenomenological approach (i.e. that perceptual experience was nativist, innate to the individual).
In the mid-twentieth century, greater recognition of the complexity of human perception saw growth in the transactional functionalism approach which emphasized perceptual experience in interpreting images, and the new look which emphasized individual differences in motivation, emotion and personality in influencing what is seen (Bruce & Green, 1990).
From the 1950s, a revolution in psychology occurred as it moved from the behavioral approach to the cognitive information processing model, a shift from focusing on the external behavior to the internal processes within the brain. Brains do not simply respond to the stimuli of the senses; they also process the information received and decide what to do and what to retain in memory. Neither the perceiver’s visual experience nor his overt responses are immediate results of stimulation. They are consequences of processes, or a sequence of processes, each of which takes a finite amount of time (Haber & Hershenson, 1973)
During the 1950s and 1960s, psychologists viewed the brain as a computer, with its various functions – input, central processing, memory, output (Figure 1), but because the computer analogy does not explain how the process works, use of this analogy has diminished.
Just as the computer codes information, stores and processes it and produces an output, so environmental information is received by the senses and then processed by various systems, including perception, sensory memory, short-term and long-term memory which transform the information and upon which the brain then acts. Visual information received by the eye is coded into electrical neural activities, which are stored by the brain and used, for example, in reading.
Human cognitive ability relies on the brain’s information processing capability and the knowledge it has stored in its short and long-term memory. The short-term memory has a limited capacity of about seven pieces of information, but the long-term memory appears to have no limit. Some models also include a sensory memory component which holds information from the senses for a very short period before processing, and a working memory component.
There are many variations of the information processing model, but the common features are:
- Environmental inputs via the five senses;
- Sensory memory which processes the sensory information in 0.5 – 3 seconds and transfers it to the short-term memory. Sensory memory also selects information from the senses, for example, focusing on one conversation in a noisy room rather than on all the other conversations;
- Short-term memory and working memory which receive the sensory information and gives it meaning through organization and inference, compares it with knowledge from the long-term memory, and if necessary, initiates action. The short-term memory retains information for only 5 – 15 seconds after which it is either forgotten or transferred to the long-term memory (Table 1). Repeating the information, such as rehearsing a telephone number between looking it up and dialing it, appears to be essential for the information to be retained by the short-term memory. The duration of short-term memory is longer when rehearsal is used.
- Long-term memory, a permanent repository which passively holds acquired knowledge. There is no practical limit to the capacity of long-term memory, the brain containing approximately 100 billion (1011) neurons each capable of storing a reasonable amount of information. Retrieval of information from long-term memory is rapid, despite the billions of choices available (Lindsay & Norman, 1977).
Table 1 Forms and functions of memories
The information processing approach to perception arose from the realization that a perceptual experience does not comprise simply viewing an object or scene – which ends as the viewing ceases – but includes the ongoing human processing at the source of the stimulation. This continuum of experience is a major assumption of the information processing approach. An analogy is the memories associated with going on a holiday, firstly, the anticipation, secondly the holiday, and thirdly the recall of it afterwards. All comprise the holiday memory.
Figure 2 illustrates the components of the information processing model. It includes a separate cognitive processing component which some models include (e.g. jaredmgriffin. wordpress.com). Memory is a storage function, not an executive function which logically must be separate. Relatively little is known about the cerebral mechanisms involved in processing information at the various stages, although research indicates that many parts of the brain are working conjointly and continuously – not separately and at different times. The process is not necessarily entirely linear as the model may suggest: different stages affect one another (Spoehr & Lehmkuhle, 1982). The model differentiates between the reception of the sensory information and its immediate internal representation (Kant also distinguished between the actual scene and the mind’s eye representation of it). Although the model indicates that some information is lost through forgetting, some savants can recall every feature of houses on a road along which they walked decades previously. In addition, events which are no longer cognitively retrievable may be recalled through hypnosis so it is possible that nothing is lost.
By the latter twentieth century, information processing was the dominant psychological approach to perception.
Environmental psychology grew out of the work of Edwin Boring at Chicago in the 1940s and in Kansas, the work of Roger Barker during the 1950s and 1960s at the Midwest Psychological Field Station. Boring and Baker initiated research into the influence upon people of their surroundings and “legitimized psychological research conducted in real-world settings as well as in the psychological laboratory” (Holahan, 1982). Describing their work as ecological psychology they demonstrated that behavior could not be predicted upon the basis of individual differences in background or personality alone but had to take account of the environmental setting.
Various psychologists studied aspects of this and in the 1960s, these interests coalesced into the distinct and independent area of environmental psychology. This was applied in architecture, interior design and city planning. However, professionals working in these areas were frustrated by the psychologist’s inability to apply their limited research findings to practical issues of design. During the late 1960s, growing numbers of psychologists reflected the increasing community concern about the environment and extended environmental psychology into new areas of research such as environmental attitudes and perception, urban design, crowding, environmental stress, coping with natural disasters, environmental cognition and mental maps. By the 1970s, environmental psychology became an accepted field within the social and behavioral sciences (Holahan, 1982).
A growing number of psychologists have studied human behavior and environmental preferences within an outdoor setting, where the complexity of the environment makes it difficult to evaluate the contribution of the various stimuli. An armory of sophisticated public survey instruments and statistical analysis tools have been developed to apply in such settings.
VISUAL PERCEPTION MECHANISMS AND MODELS
One of the consequences of psychophysical research is that its focus upon the processes and measurement of perception has been at the expense of research into the content of perception – content free understanding. An information-processing approach does not in itself demand attention to the perceived qualities of the visual world. … many of the models … have no components that are concerned with the way things look (Haber & Hershenson, 1973). This qualification is important in the study of landscape.
In this section, the laws governing perception are summarized, the concept of visual space and perception of visual form examined, and the principles of perception defined. We start by looking at the physics of the eye.
Physics of the Eye
Of prime importance in viewing landscapes is the application of the information processing model to the dominant sense of sight. The following summarizes aspects of the physics of the eye. The physical characteristics of the eye together with its neuro-physiology are not examined as there are many references available to provide details; for example, Brown, Riggs & Hsia in Graham, 1965; Haber & Hershenson, 1973; Spoehr & Lehmkuhle, 1982; Bruce & Green, 1990.
The Lambert is the luminance of any extended source or surface emitting or reflecting one lumen per square centimeter of its surface. This is equivalent to the luminance of a perfectly reflecting and diffusing surface at a distance of one centimeter from a point source of one candlepower. A millilambert is 0.001 Lambert (Graham, 1965).
The eye responds to light levels over a range of 1013 millilamberts (ml), extending from below the intensity of starlight on white paper (10-6 ml), through moonlight on white paper (10-2 ml), comfortable reading light (1 ml), sunlight on white paper (104 ml), a tungsten filament (107 ml), to the intensity of light on the surface of the sun (1010 ml) (Graham, 1965).
The visual field of the human eye is about 200º, (i.e. extending slightly behind through peripheral vision) (Figure 3). The normal visual acuity of the eye, the ability to resolve small stimuli, is 0.5 seconds of arc, which is equivalent to a line 1 mm wide at a distance of one kilometer (Day, 1969). Under ideal conditions, the eye can detect a candle at the distance of 31 miles (50 km), and a 20 cent coin can be seen at 6 miles (10 km) distance (Haber & Hershenson, 1973). Visual angles of some common objects: sun and moon 30 minutes of arc each, a thumbnail at arm’s length is 1.5º to 2º arc, a 4-letter word in a book at 50 cm is about 0.7º (Haber & Hershenson, 1973).
Eyes are in constant movement, not just following events in one’s surrounds but also making small jiggling movements called physiological nystagmus. Several types of movements can be identified: one is very small and fast with the eye moving in angles of 20 seconds of arc, 30 – 70 times a second; another is a large oscillatory motion; and yet another is a slow drift of a few minutes of arc one way or another. There are also rapid jerks, with an amplitude of 5 minutes of arc, often correcting for the slow drifts (Lindsay & Norman, 1977). In viewing a scene, the eye moves in a series of discrete jumps called saccades from one part of the scene to another. This can occur four or five times per second. Saccadic eye movements take about 200 milliseconds to complete.
Sensory information storage
At this stage, the multiple information outputs from the retina are coded “visually” for internal representation purposes. The nature of this coding and storage is not yet understood. The speed of saccadic movements of the eye gives the viewer about ¼ second in which to process the information prior to its transference to more permanent storage. The sensory information store is a very short-lived type of memory – perhaps 0.1 – 0.5 seconds. It enables visual information to be retained after the subject has disappeared (Spoehr & Lehmkuhle, 1982). Retention of such information by rehearsal cannot be undertaken as it is in the short-term memory store. More information is stored in the sensory information store than can be extracted, implying some sort of limit by later stages. For example, the memory retains that which is of value (Lindsay & Norman, 1977).
Visual Image Representation
Information about the scene passes to the short-term memory and also to the visual image’s representation – the mind’s eye of what is seen by the eye. Successive saccades of the scene are integrated with previous ones to construct an integrated image. This is not a photographic image but one that follows the rules of perceptual organization. These include figure-ground segregation and the Gestalt perceptual laws which include proximity, similarity, symmetry, closure and continuation.
Concept of Visual Angle (Euclid’s Law)
Figure 4 illustrates the concept of the visual angle. The angular size of the object is inversely proportional to the distance of the physical object from the eye – this is Euclid’s law of the visual angle. An object of given height will subtend a larger angle when viewed from nearby than when viewed from a more distant location. Foreshortening occurs when an object such as a book is not on a frontal plane (i.e. at right angles to the line of sight) but rather is angled backwards so that the image of the book is smaller and its shape distorted.This explains the convergence of parallel lines formed by roads, railways and fences, which are not on a frontal plane and also why the individual components in an area of brick paving or leaves on the ground become increasingly compressed with distance. The visual angle subtended by the objects and by the separation of spaces between objects decreases with distance (Rock, 1984).
The geometry of Euclid’s law is that for the visual angle Ø: Tan Ø/2 = h/2d
where h is the size of the object and d is its distance from the eye
Where Ø is small (i.e. so that tan Ø = Ø) then Ø = h/d in radians or Ø = 57.3 h/d in degrees. Thus if Ø is 10º, this equation will overestimate it by only 1% (Graham, 1965).
Law of Size Constancy (Emmert’s Law)
Size constancy (i.e. an object is the same size regardless of the size of the image) links with the concept of shape constancy (i.e. that an object has the same shape despite changes in the shape of its image) and orientation constancy (i.e. that an object is the same despite its orientation).
The law of size constancy (Figure 5) indicates that the perceived size of an object of constant angular size is directly proportional to its apparent distance. The term ‘apparent distance’ means its perceived distance, which is not necessarily the same as its actual distance. Similarly, size is as perceived rather than necessarily its actual size.
Perception of visual space is highly relevant to the perception of physical landscapes as it involves the perception of various subtle cues (e.g. depth and perspective) which give the landscape its characteristic dimensions. Three-dimensional space is considered by some to be paralleled by an internal representation that orients visual objects and even imaginary objects, including the viewer’s own body relative to the axes of this internal three-dimensional space (Attneave, 1972). A similar view is that relations in perceived space determine perception; perceived space being an internal representation of space that provides an internal frame of reference. There has been some experimental evidence in support of the idea of internal representation of three-dimensional space (Kaufman, 1979).
Berkeley (1709) believed that the depth in a scene was not based on anything in the scene itself; rather depth was learnt (e.g. tactually). It is now known that Berkeley was wrong, in that cues in the scene indicate its depth. However, he was correct in that cues have to be learnt. Cues to depth in a scene include those shown in Figure 6.
The hidden figure in the interposition case in Figure 6 is considered to be more distant than the one that hides it. The reason the interposition cue is seen as two circles rather than a circle and a crescent is explained by the Gestalt law of good continuation, which holds that we tend to minimize change or discontinuity. Hochberg established a similar principle, that when a figure allows for alternative descriptions, we perceive the simplest one (Kaufman, 1979). Interposition can also enable one to judge the relative distance of an object, in contrast to its absolute or actual distance. How distance is perceived and used to calibrate the representation of space is one of the challenges facing research in perception.
There are additional cues to those illustrated:
- Aerial perspective Distant objects are tinged with blue coloration such as the haze of distance which is so evident in Australia. The cue involves conditions in which the requisite visual contrasts are absent (Graham, 1965).
- Detail perspective The loss of visible detail of distant objects because of limitations of visual acuity and the scattering of light by the atmosphere is known as detail perspective. Detail perspective and aerial perspective were cues used by Leonardo da Vinci and other painters of the Renaissance to give the impression of depth in paintings (Rock, 1984).
- Texture gradient The image of a large number of regular textures receding into the distance creates a gradient of image size (Bruce & Green, 1990).
- Shadows on the sides of hills and valleys provide an impression of depth; attached shadows reflect the depth of within an object itself while cast shadows are those that fall on surrounding surfaces. Attached shadows give a strong sense of depth, while cast shadows are somewhat divorced from the object itself and provide little or no cue to depth (Rock, 1984).
- Motion perspective This is a kinetic cue which involves distant objects appearing to be virtually stationary when one moves past them, while nearby objects move swiftly past. “Objects nearby seem to be moving away from you at a velocity that increases the closer the objects are” (Kaufman, 1979).
- Kinetic cues Movement provides information about depth and distance that is not evident from a single static view. People with monocular vision estimate depth by movement.
- Familiarity of objects Familiar objects such as a person, a car, electricity pole or a tree can provide a yardstick against which the distance and size of other nearby objects can be estimated.
The presence of several cues provides the brain with strong evidence of depth, although the means by which cues are interpreted collectively is not understood.
Through working with student air pilots during the Second World War and finding that the tests for cues for depth gave no indication of their success or failure in the air, James Gibson realized that the traditional list of cues for depth was inadequate. He came to believe that the whole theory of depth perception was false. In its place, in 1950, he developed a ground theory of space perception, to be differentiated from the traditional theory, which he termed air theory. He considered that there is literally no such thing as perception of space without the perception of a continuous background surface (Gibson, 1979). Thus the world did not comprise bodies in the empty air (such as aircraft) but rather a basic surface with adjoining surfaces. The character of the visual world was given not by objects but by the background of the objects. The parallel with the figure/ground principle of Gestalt psychology is obvious.
Perception of Visual Form
Definition of forms
The dictionary defines form as the visible aspect of a thing (Shorter Oxford Dictionary), but in psychological terms, it is difficult to provide a precise, quantifiable definition. Uttal, an authority in perception research, admits that the scientific community has not succeeded in defining precisely what it is that we mean by the word ‘form.’ We have progressed only modestly beyond the Gestalt notion that form is ‘any segregated whole or unit’ (Uttal, 1983). There have been attempts to specify forms statistically as classes of forms. Following a comprehensive review of the literature, Zusne proposed as an interim definition “… form may be considered both a one dimensional emergent of its physical dimensions and a multidimensional variable” (Uttal, 1983).
Homogeneous fields prevent discrimination of objects, although such fields are relatively rare in nature (e.g. pitch-black night, dense fog, snow storm or sand storm). Objects are commonly seen against a background or a surface, providing an inhomogeneity in the retinal projection that results in a perceptual segregation of the visual field into figure and ground. This is the first stage in the organization and synthesis of form.
Characteristics of the figure compared with the ground are summarized in Table 2. The structure of the figure derives from its contour; the strength of its contour will determine the degree by which the figure stands out from the ground.
Table 2 Figure and ground characteristics
Based on Haber & Hershensen, 1973; Bruce & Green, 1990; Graham, 1965.
Visual fields that are completely homogeneous are called Ganzfelds (e.g. looking through a dense fog without borders, edges or bright areas). Closing the eyelids forms Ganzfelds, reducing stimulation – after a few minutes, the neural excitation leaving the retina is reduced to negligible levels. Ganzfelds research has shown the importance of spatial inhomogeneity – variations across the visual field, and temporal changes in the field. Contours or variations are indispensable for form perception.
Earlier reference was made to saccades (small movements of the eye). Such movements enhance the sensitivity of the visual system (Haber & Hershenson, 1973). It has been found that when the visual image upon the retina is stablized, perception diminishes quickly but that perception is reinstated by movement, by changing the stimulus over time or by brightening the luminance.
The research suggests that variation in stimulation of the retina is necessary for perception to occur.
Principles of Perception
Irvin Rock (1975) defined nine principles of perception. The term ‘proximal stimulus’ refers to the retinal image of a particular surface (i.e. that which the eye sees).
- The proximal stimulus array must be considered to be ambiguous as to what it represents in the world.
- Perception begins with a process of grouping and figure-ground organization of the proximal stimulus.
- The organization achieved is based on a selection, decision, or preference for certain outcomes on the part of the perceptual system.
- The central events that lead to particular perceptions are not themselves subjectively experienced (i.e. they are not conscious).
- As a rule, what is perceived does not simply correspond directly with the relevant feature of the proximal stimulus (e.g. perceived size with the object’s visual angle).
- The facts of perception cannot be fully explained by the operation of physiological detector mechanisms such as are triggered by a particular stimulus impinging upon the retina.
- What is perceived is generally, although by no means always, veridical (veridical means truthfully reflecting the objective state of affairs rather than illusory).
- Perception generally is not influenced by knowledge (in contrast to sensory information), i.e. what we perceive is not determined or affected by what is known about the object.
- Vision is dominant over other sense modalities so that not only does it tend to determine what is perceived when a sensory conflict occurs, but it also tends to ‘capture’ and thereby distort the very experience of the object as given by that other modality.
In summary, what we see is perceptually organized and scaled, is the objective (not illusory) fact, is not influenced by prior knowledge, and takes priority coming from the other senses.
ENVIRONMENTAL PSYCHOLOGICAL APPROACHES TO PERCEPTION
The development of environmental perception grew out of the interest of psychologists in the environment in the 1960s and 1970s, although one of the earliest, James Gibson, began to develop his theory in the 1940s. The Gestalt theory is also a precursor to environmental psychology. The Gestalt emphases on perception as a holistic process and on the dynamic, organizing aspect of perception have influenced much of the later research and theorizing in this area (Holahan, 1982). Some of the following examples stray into the area of environmental aesthetics.
The term distal stimulus describes what is being viewed such as a landscape, while proximal stimulus is the image of the view by the retina of the eye. A percept is the brain’s reconstruction of the landscape.
James Gibson (1904 – 1979)
James J. Gibson’s Ecological Theory proposes that environmental perception is entirely a function of the stimulation received from the environment (i.e. humans do not interpret and construct meanings from this interaction). In Gibson’s terms, humans receive information direct from the environment and view it holistically as a meaningful entity rather than in a disaggregated way. An environment’s permanent physical properties are termed affordances, denoting the functional properties that an object affords (e.g. a sturdy, non-porous object with interior space affords shelter; flat surfaces raised off the ground affords sitting). As we explore and experience an environment, we become aware of affordances that help us make use of the environment.
Gibson attributes the origin of the concept of affordances to Koffka, the Gestalt psychologist who described the “demand character” of an object:
To primitive man each thing says what it is and what he ought to do with it … a fruit says “Eat me”; water says “Drink me”; thunder says “Fear me”; and woman says “Love me” (Gibson, 1979).
Gibson’s concept is that perception is based upon the use of elements (i.e. their affordances) rather than their form, color and other attributes. Buildings are not seen as forms but rather as functional spaces in which we work and live. The environment offers affordances to animals or humans. Gibson states: This is a radical hypothesis, for it implies that the ‘values’ and ‘meanings’ of things in the environment can be directly perceived. Affordances are very varied:
“Surfaces afford posture, locomotion, collision, manipulation, and in general, behavior. Special forms of layout afford shelter and concealment. Fires afford warming and burning. Detached objects – tools, utensils, weapons – afford special types of behavior to primates and humans.”
Gibson believes that animals, including humans, have evolved ways of detecting invariant information about the environment, which enables them to perceive affordances. These do not derive from memory but from the perceptual system, which has evolved to “resonate” with this information. Gibson leaves vague the notion of resonance (Bruce & Green, 1990).
Gibson’s approach is a radical departure from the mainstream perceptual psychology.
“Traditional perceptual theory holds that perception is indirect and mediated by higher cognitive processes. We do not ‘just see’ the world but actively construct it from fragmentary perceptual data. Gibson is a ‘direct realist’. He holds that perception is direct and unmediated by inference and problem solving” (Bruce & Green, 1990).
His theory focuses attention on the environment but has generally been regarded as inadequate to explain human/environment interactions. Jay Appleton’s prospects and refuges may be regarded as affordances.
Egon Brunswik (1903 – 1955)
Egon Brunswik’s lens model of environmental perception describes the interpretative role the individual plays in perceiving a scene – a process whereby the scattered environmental stimuli (the objectively measurable characteristics of a scene) are recombined by the viewer as a lens focuses light. It emphasizes the individual’s active interpretation of sensory information received from the environment. Such information is never perfectly correlated with the real environment and complex and sometimes misleading cues can be received (e.g. the human eye has to judge how far away an object is based upon the size of the object and the setting). Brunswik’s model is also known as a Probabilistic Functionalism model. Figure 7 illustrates the lens model, showing the zones of ambiguity between the distal variable on the left and the judgement on the right.
We make a probabilistic estimate of the distance that is a ‘best bet’. Brunswik described it thus:
“The best (the individual) can do is to compromise between cues so that his posit approaches the ‘best bet’ on the basis of all the probabilities or past relative frequencies or relevant interrelationships lumped together” (Ittleson, 1974).
Perception involves extracting useful cues from a scene of many potentially confusing cues. The individual thus plays an active role in interpreting information from the environment based on a repertoire of probabilistic statements from many settings. As there are many possible environments, judgements about any particular environment cannot be absolutely certain – only probabilistic estimates.
While there are many representations of the model, all contain the following seven elements:
- The distal variable which is the object of view and of judgement;
- Cues or proximal variables;
- Judgement about the distal variable based on the cues;
- Cue validities between the cues and the distal variable which are imperfect;
- Cue utilizations, also imperfect, between the cues and the judgement;
- Interrelationships between the cues;
- The relation between the cue and the judgement known as accuracy or achievement.
Figure 8 illustrates the subjective assessment of a landscape, through the integration of its distal and proximal cues to provide the observer’s perception of the scene.
The probabilistic model is rather more widely accepted than Gibson’s ecological model. Ames’ transactional psychology takes Brunswik’s model further by emphasizing the dynamic and creative role of the individual in environmental percep-tion. Each individual builds a unique store of environmental interactions – “the world each of us knows is a world created in a large measure from our experience in dealing with the environment” (Holahan, 1982). The probabilistic model is a basis for research on organism-environment relationships in which greater emphasis than is usual is placed on situation sampling rather than subject sampling so that the environment’s influence on behavior might be better understood.
Anton Ehrenzweig (1908 – 1966)
Ehrenzweig addressed aesthetics through combining the Gestalt and psychoanalytical approaches. He drew from Nietzsche’s book, “The Origins of the Tragedy from the Spirit of Music” in which Nietzsche laid down the principles of Apollonian and Dionysian form.
While the Dionysian principle stands for chaos and destruction, the Apollonian stands for order and beauty which “have been transfigured into the sublimity and grace of ‘classical beauty’.” In Gestalt terms, this is equivalent to the operation of the Prägnanz principle (see Gestalt) bringing balance and order.
The classical Apollonian order of landscapes has been very influential in public taste since the eighteenth century when the “picturesque” style was introduced based on Italian art, in particular, that of Claude Lorraine, who painted elegant pastoral landscapes of the golden classical age (see theme: Landscape art). The creation of imagined classical order from chaos and degradation, reflected the influence of the Prägnanz principle.
The Dionysian influence has the power to excite but after the excitement passes it can become ugly and “old fashioned,” much like Victorian clothes and ornate manner of style. Over time, however, the Prägnanz effect of “bump erasing” removes the unnecessary detail and crystallizes a new, simple line and stylistic purity from the old, an example of good Gestalt. While Lorraine’s exaggerated stylistic detailing of classical landscapes is no longer appreciated, a simplified form that captures the essential elements of his style continues to the present day.
Daniel Berlyne (1924 – 1976)
In contrast to Gibson and Brunswik, Daniel Berlyne focused on neither the individual nor the environment in isolation but rather on their interaction. He found that aesthetic preferences are related to the complexity of a stimulus. Like an inverted U (∩), as complexity of a scene increases so too does its attractiveness up to a point beyond which increased complexity is viewed as less pleasant. Many experiments have been undertaken to investigate the optimum levels of stimulation (Holahan, 1982). Berlyne suggests an environment’s stimulation to derive from the characteristics which cause the observer to compare or investigate further – which he termed its collative stimulus properties. These properties include:
- Complexity – a large variety of elements in the display;
- Surprisingness – unexpected elements;
- Novelty – newness to the observer;
- Incongruity – something out of place.
These properties influence an observer’s aesthetic judgements about a scene and also their desire to explore. Berlyne considered that aesthetic judgements and exploration are a combination of two factors:
- Hedonic tone: degree of pleasantness or beauty;
- Uncertainty-arousal: the inverted U (∩).
As uncertainty increases, hedonic tone (i.e. pleasantness) first increases then decreases (Figure 9).
People appear happiest at intermediate levels of stimulation or uncertainty and do not like excessive stimulation or excessive arousal. Therefore, one might expect that landscapes that are intermediate in complexity, novelty, incongruity, and surprisingness would be judged the most beautiful, whereas landscapes that are low or high in these collative properties would be regarded as less attractive.
While Berlyne’s theory has appeal, it is not supported by the evidence of viewing natural landscapes. Studies have supported the ‘∩’ in relation to non-environmental stimuli (e.g. paintings, music) and possibly for urban environments, however, Wohlwill, Kaplan and others contend that in natural environments, preferences increase linearly with complexity (Wohlwill, 1976). Somewhat surprisingly, the researchers found it impossible to find natural scenes containing the degree of complexity comparable with the human-made environment at the upper end of the scale (Figure 10). In the mixed set, the relationship did not appear to be consistently related to complexity.
The findings support research findings (notably by Stephen and Rachel Kaplan) that the significant variable was between natural and human-made, there being a higher preference for natural scenes compared with human-made scenes. Joachim Wohlwill has considered the environment as a source of affect producing feelings of pleasure or aversion. Stimulus attributes – complexity, incongruity, novelty, familiarity and variety produce these feelings. Wohlwill suggests that fittingness, or how well an element (e.g. a house) suits a certain setting (e.g. wilderness) is an additional collative property.
Stephen and Rachel Kaplan
Stephen and Rachel Kaplan employ an information processing approach to explain the interactions between humans and the landscape. The Kaplans hypothesize that “the perceptual process involves extracting information from one’s environment” (Kaplan, Kaplan & Brown, 1989). They identify four predictor variables, two of which (coherence and legibility) help in understanding the environment, and the other two (complexity and mystery) encourage its exploration. The Kaplans contend that humans seek to make sense of the environment and to be involved in it.
Underlying the Kaplan’s approach is an evolutionary view that human preferences derive from the adaptive value offered by particular settings (Kaplan, S, 1987). One of the supporting factors cited is the preference for savannah landscapes over other biomes found among young children (Balling & Falk, 1982). A further factor is that manipulated landscapes such as ornamental gardens and municipal parks tend to reflect the scattered trees of a savannah landscape. A third strand of evidence cited by Kaplan is Appleton’s prospect and refuge theory (1975), the notion of seeing without being seen, in which preferences are for those settings which provide advantage for hunting or hiding. The Kaplan’s theory is detailed in Theory of Landscape Aesthetics.
A somewhat piecemeal picture of the psychology of perception emerges because perception has not had a single stream of development growing and becoming more sophisticated in its evolution but rather is characterized by varying approaches. In more recent decades, there has been considerable fundamental research of the neurophysiology of perception, far removed from environmental perception. The abundance of competing theories of perception and environmental perception, in particular, are indicative of any developing field of inquiry. It is doubtful whether this is likely to change soon.
Regarding the contribution of psychology to the study of beauty, Sachs (1951) remarked with prescience:
“The great bulk of investigation about the nature of beauty has been piled up by metaphysical speculations or elaborated as part of some system of philosophy. As everyone knows, the approach by observation of facts and by experiment is a comparatively modern innovation, and this is especially true in matters concerning the mind; anything so obviously connected with a man’s soul was considered the exclusive domain of philosophy, metaphysics and theology. Psychology, the latest of the late, was welcomed not too warmly when it tried to squeeze itself into an already overcrowded space. The bias of this present attempt (i.e. Sachs’ book) is clearly on the side of psychology, trying to get elbow-room for it, even at the cost of some older occupants.”
Despite being a relative newcomer compared with philosophy, psychology has contributed profound insights and knowledge to the understanding of aesthetics.
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