Background Information on Visual Perception

Look at the picture above. What do you see? To most people, the picture initially appears as a meaningless array of shadings and dots. With time, however, people begin to organize the elements of the picture and they eventually recognize the figure of a dog hidden within the shadings and dots of the picture. This example demonstrates that sometimes we cannot perceive things that actually exist.

Now look at the picture above. Do you see the white triangle in the center of the image? The foreground of the image, the reversed upside-down triangle and the three black circles, highlights the white triangle, making it hard to miss. Now imagine the picture without the three packman-like figures surrounding the white triangle. Do you still see the white triangle? This example demonstrates that sometimes we perceive things that do not actually exist.

The preceding demonstrations are examples of perceptual illusions. Perceptual illusions are errors of perception, which occur when we perceive stimuli as something other than what they really are. “The existence of perceptual illusions suggests that what we sense (in our sensory organs) is not necessarily what we perceive (in our minds)” (Sternberg 111). Research on perceptual illusions, and their associated perceptual errors, has shown the act of sensation is not the same as the act of perception.

Sensation is the process by which sensory information from the environment stimulates the appropriate sensory receptors of our eyes, ears, nose, skin, and mouth (113). While perception is the “set of processes by which we recognize, organize, and make sense of the sensations we receive from environmental stimuli” (Epstein & Rogers, 1995; Goodale, 2000a, 2000b; Kossyln & Osherson, 1995). A brief review of James Gibson’s (1966, 1979) concepts of distal object, information medium, proximal stimulation, and perceptual object will provide a framework for understanding how the distinct processes of sensation and perception function as part of a perceptual continuum through which environmental stimuli are senses and perceived.

Gibson proposed that distal objects, which are objects in the external world, “impose patterns on an informational medium” (Sternberg 113). When the informational medium, which is the patterns of sound waves, chemical molecules, tactile information, or reflected light coming from the distal object, contact the appropriate sensory receptors of the eyes, ears, nose, skin, or mouth, proximal stimulation occurs (113). Lastly, perception occurs when an internal perceptual object reflects, in some degree, the distal object. The following example illustrates how visual information moves through this framework.

The red refrigerator pictured above is an example of a distal object. Although we are not consciously aware of it, the refrigerator is reflecting patterns of light; visible electromagnetic waves, the informational medium, convey these patterns to our eyes. When those waves contact the sensory receptors of our eyes, proximal stimulation occurs and our rods and cones are stimulated. At this stage, we are not consciously aware of what we are seeing. Finally, visual perception recognizes the waves and organizes them into a mental replication of the distal object, making us consciously aware that we are looking at a red refrigerator. The specific processes by which visual perception recognizes and organizes visual stimuli, which ultimately determines what we perceive, are not really known. It is important to note that visual perception does not just recognize and organize visual stimuli coming from objects, which we consciously look at; rather, visual perception processes all visual sensations.

The sensory receptors of our eyes are continually bombarded by visual stimuli from the environment. Very little of what is sensed by our sight receptors, however, is consciously perceived by the brain. D. E. Berylne suggests that “…only a minute proportion—certainly less than 1 percent—of the information coming in from the environment...” is consciously perceived by the brain (Berylne 98). This is because visual perception, in its processes of reorganization and organization, decides which visual stimuli are relevant and should be perceived and rejects visual stimuli that are irrelevant. We know that this regulatory aspect of Contextual perception exists to prevent us from overloading the limited capacity of our nervous systems and to enable us to efficiently select the most vital visual information from our environment so that we can quickly respond in a manner which is beneficial to our survival (97-98). We do not know, however, the processes by which visual perception decides which visual stimuli are to be perceived and which is to be ignored.

Theories of Contextual Perception

In general, the various theories of Contextual perception seek to explain the processes by which visual stimuli are recognized, organized, and consequently perceived. There are two main classes of perception, each with their own theories:

BOTTOM-UP
Bottom-up theories propose that perception starts at the bottom with, “the physical stimulus—the observable form or pattern—being perceived and then working their way up to higher-order cognitive processes, such as organizing principles and concepts” (Sternberg 126). Bottom-up theories do not require higher cognitive processes.

Five main Bottom-up theories:

Direct perception
The information contained in our sensory receptors, including the sensory context, is all wee need to perceive anything. No higher cognitive processes or internal representations are necessary.

Template/Exemplar theories
We mentally store examples of all the objects we have seen as templates, which are detailed models of patterns we might encounter. We recognize a pattern by comparing it with our stored templates and choosing an exact match.

Prototype theories
In place of rigid templates, we store a prototype, which is the most recognizable example of an object. We compare a perceived object to these prototypes until we find the closest match.

Feature theories
Perception results from matching features of an object with features stored in memory.

Structural description theory
We observe the lines and corners of objects and use this information to deconstruct them into their basic geometric shapes, called geons. We perceive objects by matching those geons with our stored geons.

TOP-DOWN
Top-down theories propose that higher-level cognitive processes, such as knowledge and context, are employed to make meaning out of basic features.

The primary top-down theory is constructive perception.
We construct “a cognitive understanding (perception) of a stimulus, using sensory information as the foundation for the structure but also using other sources of information to build the perception.” (Sternberg 113).

Background on How We Assign Value and Meaning

Berlyne back in the 1970s analyzed hedonic properties of artwork and objects and “linked hedonic value to three main classes of stimulus variable: collative variables (particularly novelty and complexity), psychophysical variables (such as intensity and brightness) and ecological values (meaningfulness and associative values)”(Russell, 2003). In this website we are mainly concerned with exploring what Berlyne termed ecological values, and how the context or environment of an object affects this assigning of meaning and value.

The Hedonic Theory

Explanatory Information, Meaning Making and Value
One of the contextual variables in an object or art viewing environment, is the amount of information or background you are given regarding the item. For example, when you are viewing a painting do you know the title? What does it tell you about the painting or the artist’s intention? Are you aware of any additional information such as what the impetuous behind the painting or what was going on in the personal life of the painting? Phil Russell conducted experiments to test the hypothesis that giving individuals additional information in the form of a title or background notes would increase the meaning and hedonic value of the object for the viewer. Meaning in this context is defined as being able to “understand the painting, make sense of it, and see what it represented” (Russell, 2003). This point was illustrated using abstract art or ambiguous art? Title and background notes can tell the viewer what the artist intended. The viewer then feels he/she is more able to understand the object and its meaning, personally and culturally. Furthermore, understanding the context for creation increases this understanding and meaning. Art is a means of communication between the artist and the viewer of the artwork. Viewers that do not understand or feel they understand, what is being said, are frustrated and will not value or assign personal or cultural meaning to the object.

An interesting note concerning the increase of hedonic value associated with additional interpretive information, are the positive or negative connotations of the information. The hedonic value may actually go down if the viewer feels the additional information associates negative feelings or thoughts with the object. For example, learning that a photograph or painting was created by mass murderer would lead a viewer to feel differently about an object regardless of its artistic merits.

Contextual Variables Such As Contrast Effects
Context dependency for information perception and interpretation has also been explained by what are termed “contrast effects and halo effects”. The contrast effect is essentially the idea that all stimuli are judged relative to the stimuli around them. Contrast effects were first experimentally supported in 1958 by Sherif, Taub and Hovland. They had subjects lift weights in different orders and then rate them according to their perception of heaviness. If the subject lifted a heavy weight before a lighter weight, he would rate the second weight as lighter than those rating them in the reverse order. This effect is generalized to all of our sensual perceptions and the ecological values associated with them.

Plous also experimented with contrast effects in relation to “inferring what you want from what is available” (Plous, 1997). How do the selection of objects and their qualities affect your judgment? If there is only one type of wine on a shelf and it seems reasonably priced, you may be satisfied with the item. Suppose there are several other wine bottles added to the shelf and now the initial bottle appears to be the most or least expensive, does it change the value you associate with it? What if some appear physically more attractive than others? What if some are given endorsements?

Codes for Context
When observing a specific object, how does the physical context or environment influence how you value the object financially, personally or culturally? As members of a specific culture existing in a specific time and place, we design and agree upon a set of rules or code “to define what is and is not art and design and to distinguish one form of art or design from another”(Barnard, p. 125). What are some external (referring to outside the object) cues involved in this process of interpretation? Two of the most important are time and place. When an object is viewed in a garage sale or even a landfill we assess its value in a different way than if it is displayed in an art gallery or museum. These places denote that certain conditions have been met that ascribe to agreed upon codes in our culture. The more valuable an object is to us financially, personally or culturally, the more resources we will put into insuring its preservation, and prominence. We put the most resources into a museum, or a gallery. An object in a garage sale signals that the value of an object has diminished enough that it can be disposed of with very little compensation. Finally, if an object is in a landfill, we assume that an object has gone through several levels of evaluation and no longer has value on any level for members of our society.

There are also internal codes within the art and design of an object that strongly influence the impression or meaning it has for the viewer. Designers or artists usually subscribe to these internal codes in order to communicate their message, their meaning, or their use. These internal codes may be determined by their physical properties but also may have evolved over time. For example, “visible brushstrokes in a painting may signify an expressionist, rather than a realist, painting” (Bernard, 126). Once we determine according to the internal codes that a painting is expressionistic, we will interpret the meaning of the painting accordingly. We may assume that the scene represents an expression of the artist, not necessarily a duplication of the visual stimulus for it.

Coded Signs and Symbols
Just as there are agreements about time and place, there are cultural, societal and group agreements about images or objects and the ideas they represent. An image or object can retain the same physical properties but function differently based on the context in which it exists. The use of the rainbow is an illustration of this idea.

Physiology
In both bottom-up processes and top-down processes, cognitive processes are employed to help us organize and recognize patterns of Contextual stimuli. Because these processes affect how we sense visual stimuli, they also affect how we perceive visual stimuli. Lateral inhibition is one cognitive process which we use. When light enters the eye, it travels through the eye until it hits the photoreceptor cells in the rear of the eye. Once excited, the photoreceptors then inhibit the bipolar cells, which then excite the ganglion cells. When the ganglion cells are excited, however, they also inhibit neighboring ganglion cells, in proportion to their own excitation. For example, consider the following situation where ganglion cell “A” is excited by 4 neurons and ganglion cell “B” is excited by 2 neurons. A will subtract 25% of 4 from B (4 x 0.25 = 1 unit inhibition); thus B sends signal (2 photons - 1) = 1). Likewise, B subtracts 25% of 2 from A (2 X 0.25 = 0.5 unit inhibition); and A sends signal (4 photons - 0.5) = 3.5. Thus, lateral inhibition causes the actual illumination of 4:2 to be perceived as 7:2 by the brain; thereby intensifying the differences in the visual field.