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VISUAL PERCEPTION
Visual perception is the end product of vision, consisting of the ability to detect light and interpret (see) the consequences of light stimuli. The resulting perception is known as eyesight, sight or naked eye vision. Vision has a specific sensory system, the visual system.
The visual system
The eye focuses light on the retina, which turns light into neural impulses and performs the first stages of processing on those signals. The remaining stages include the lateral geniculate nucleus, and the primary and secondary visual cortex of the brain.
A recent University of Pennsylvania study calculated the approximate bandwidth of human retinas as 8.75 megabits per second, whereas guinea pig retinas transfer at 875 kilobits. [1]
Theoretical perspectives in the study of visual perception
The major problem in visual perception is that what people see is not simply a translation of retinal stimuli (i.e., the image on the retina). Thus people interested in perception have long struggled to explain what visual processing does to create what we actually see.
Unconscious inference
Hermann von Helmholtz is often credited with the founding of the scientific study of visual perception. Helmholtz held vision to be a form of unconscious inference: vision is a matter of deriving a probable interpretation for incomplete data.
Inference requires prior assumptions about the world: two well-known assumptions that we make in processing visual information are that light comes from above, and that objects are viewed from above and not below. The study of visual illusions (cases when the inference process goes wrong) has yielded a lot of insight into what sort of assumptions the visual system makes.
The unconscious inference hypothesis has recently been revived in so-called Bayesian studies of visual perception. Proponents of this approach consider that the visual system performs some form of Bayesian inference to derive a percept from sensory data. Models based on this idea have been used to describe various visual subsystems, such as the perception of motion or the perception of depth. An introduction can be found in Mamassian, Landy & Maloney (2002). See here [2] for a non-mathematical tutorial on these general ideas.
Gestalt theory
Gestalt psychologists working primarily in the 1930s and 1940s raised many of the research questions that are studied by vision scientists today.
The Gestalt Laws of Organization have guided the study of how people perceive visual components as organized patterns or wholes, instead of many separate parts. Gestalt is a German word that translates to "configuration or pattern". According to this theory, there are six main factors that determine how we group things according to visual perception.
- Proximity – the objects closest together are more likely to form a group.
- Similarity – objects similar in size or shape are more likely to form a group.
- Closure – our brains add missing components to complete a larger pattern.
- Symmetry – symmetrical items are more likely to group together.
- Common fate – items moving in the same direction are more likely to group together.
- Continuity – once a pattern is formed, it is more likely to continue even if the elements are redistributed.
It has also been shown that certain individual differences such as impairment of sight and spatial skills can also affect our visual perception. There are also other factors that influence how we perceive things such as personality, cognitive styles, gender, occupation, age, values, attitudes, motivation, beliefs, etc.
Ecological psychology
Psychologist James J. Gibson developed a theoretical perspective on vision that is radically different from that of Helmholtz. Gibson considers that enough visual perception is available in normal environments to allow for veridical perception (accurate perception of the world). Gibson replaces inference with information pickup. Although most researchers today feel closer to Helmholtz's unconscious inference theory, Gibson has done much in identifying what sort of information is available to the visual system.
References
- Arnheim Rudolph (1954). Art and Visual Perception: A Psychology of the Creative Eye. Berkeley: University of California Press.
- Barlow H, Blakemore C (1990/1991) Images and Understanding, Cambridge, UK, Cambridge University Press.
- Helmholtz Hermann Von (2000), reprinted from 1865/1866 edition, The Treatise On Physiolological Optics, Thoemmes Continuum.
- Kleine-Horst Lothar (2001). Empiristic Theory of Visual Gestalt Perception. Hierarchy and Interactions of Visual Functions. Koeln: Enane. ISBN 3-928955-42X
- Palmer Stephen E., (1999) Vision Science: Photons To Phenomenology, Bradford Books.
- Purves D, Lotto B, (2003) Why We See What We Do: An Empirical Theory of Vision, Sunderland, MA: Sinauer Associates.
- Rodieck RW, (1998) The First Steps In Seeing, Sunderland, MA: Sinauer Associates.
See also
Types of visual perception
Disorders/Dysfunctions
Related Disciplines
Other
External links
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