Decision Theory of Perception vs Visual Theory of Perception - Essay Example

Theories of Perception Decision Theory of Perception Vs. Visual Theory of Perception Perception involves classification in terms of categories that can be applied to a plurality of objects that makes us aware of affordances with regard to epistemic operations like induction, object recognition, and object comparison, and it is consciously presented and recorded in memory in a way that makes it possible to recall the experience to consciousness. (Matthen, 2005, p. 271) The key theories of perception adopt two possible approaches in order to justify the analysis of explaining its child theories or sub theories. There are many perceptual researchers who believe that the essence of visual perception is that it is a knowledge-driven process. Perception is essentially a constructive process. Other workers have assumed that perception is largely the product of innate brain processes. Currently, there are many who claim that perceptual processes cannot be adequately understood until the intimate relationship between perceivers and the environment. (Gordon, 2004, p. 2) Decision Theory is all about making of decisions under conditions of uncertainty. In this case the format is not visual but is based upon noisy conditions sensed by the environment that gives rise to uncertainty. For example the static on a telephone line generate uncertainty by interfering with the ability of a receiver or an observer to detect a signal (a human voice). On the other end signal detection within us provides us with the opportunity to measure sensitivity independent of any predispositions for an observer to respond one-way or the other. Visual Theory according to Gestalt is based on two modes of perceiving, unhesitation and forceful everyday experience. To this end Koffka asked what has become the most famous question in the history of perception: ‘Why do things look as they do?’ In other words, what must be explained by perceptual theories is the stability and coherence of the world of everyday experience, the world in which surface colors are stable under different illuminants and familiar things do not change size as they recede. (Gordon, 2004, p. 14) Thus Visual Theory is a world of objects, which cannot be uncertain because it is based upon solid objects while decision theory is composed of signals and sensations, which leads us in a mode of taking decision, certain and mostly uncertain. For example, some psychologists feel that perception is direct (e.g. Gibson) and all the information needed is contained in the visual format while others believe that the brain uses past experience and other influences to construct a version of reality (e.g. Gregory). (Rookes & Willson, 2000, p. 14) Both the theories are all about the contrast of the stimulus patterns wavers between the ‘visible’ and the ‘non visible’. While taking the example of “bottom-up and top-down processing” theory of perception, we can compare and contrast between the two theories (decisive and visual) in the following manner: “Seeing is believing”, how one can recognize an object like chair, without reference to stored knowledge. Surely we only understand the concept of a chair because of our experience of seeing chairs in the past and our experience of sitting on them. All theorists, acknowledge that there has to be some matching process between sensory information and stored mental representation in order for final identification (naming) to take place. We can only know the word ‘chair’ because it is stored in memory. The difference is that data-driven theorists assume that the matching process itself operates until a match is found. The concept-driven theorists, on the other hand, assume that stored knowledge is required throughout the matching process. In other words, the question is whether our visual perceptive system can recognize a chair after analyzing its individual features like four legs, differentiating it from other objects with four legs (e.g. a table, a dog, etc.), or whether our knowledge and experience with chairs in terms of factors, such as where they are likely to be found and the different shapes they can be, helps us to recognize the object. No single theory that takes an extreme view on the use of the two processing approaches can explain all the evidence from perceptual studies. Now, if we examine the scenario from the aspect of decision theory, the question arises when the brain receives output signals of being recognized an object or a chair, how and in what circumstances the decision is taken to accept or reject the output. In this context signal detection theory tells us that we should also take into account an observer’s correct and incorrect responses when the stimulus is absent (catch trials). In this way we can directly compare the proportions of correct and incorrect responses (hits versus false alarms). Decision theory refers to report or not to report a signal relative to some level of background noise irrespective of whether or not the signal is actually there. Decision theory not only takes decisions with the help of signals including false alarms, miss or hits, it also takes into account the noises and voices and retains it while taking decision while Visual theory is not liable to take decisions as the image is already captured in the mind. If we analyze both the theories from the aspect of “sensory modalities”, which involves the contribution of five senses out of which seeing and hearing are the two basic ones, we see that each modality, whether it is ‘seeing’ or ‘hearing’ is gradually replaced with the idea of ‘sets’ of qualities. When we listen to music, we not only discriminate between them in terms of loudness or softness, but also whether they are higher or lower on a musical scale (pitch). Similarly when we look at objects, we not only discriminate whether some are brighter than others, but also according to their color and hue. Light is the stimulus for visual perception and the eye is the organ which responds to light energy. While examining two contemporary developments from the heritage of perception that are actively being pursued, we see that one concerns advances in our understanding of the nature of the stimulus-visual optics while the other is close to hearing as to how the perceptive system responds to decision making neurophysiology. The image-forming properties of the eye are quite well understood, and most aberrations of the eye can be corrected optically. One of the ways of measuring the performance of the visual system is to treat it as a physicist would a lens, by determining how faithfully it can transmit patterns of light incident upon it. One outcome of this approach has been the suggestion that the visual system is most sensitive to sharply defined contours and also to spatially periodic patterns of parallel lines (referred to as gratings). (Broerse, 1999, p. p3.28) Similarly sound is the spur of hearing which is truly a distal sense, which allows an organism to detect objects and events before they can be seen or come into physical contact, we can say that hearing is the perception which involves the dimension of ‘space’. With the possible exception of some of the most recent high-technology films and the invention of multichannel ‘surround sound’, the complementary nature of the relationship between seeing and hearing is largely lost in art and representation. When seeing and hearing are considered as distal senses, the complimentary relationship between these modalities becomes more apparent. Objects and their location are often heard long before they are seen. Even they can be heard when seeing is not possible. Perception of object characteristics needs to conform to the frame of reference within which behavior takes place, which will normally be the surface of the earth. We refer to such perceptions as geocentric. An active perceiver, whether human or animal, must recover the geocentric properties of objects, despite self-motion. Information is coded in terms of the coordinate system of the retina. Retinocentric information describes image characteristics with respect to retinal coordinates, but it is not necessarily localized in the retina. The fact that a response occurs in the visual cortex, or elsewhere, need not preclude it from being retinocentric in character. The term retinocentric expresses the nature of the information, and not its anatomical site. Information about the location of objects can only be expressed in terms of a particular frame of reference. The retina generates neural signals that carry information about the location of stimulation with respect to a retinal frame of reference. Such information is then potentially available at any later stage in the visual system, and remains retinocentric unless transformed into another frame of reference. (Swanston & Wade, 2001, p. 217) This retinocentric level is essential for vision but it cannot serve as a basis for object perception or recognition because we have two eyes and both of them move. The same function is performed by ears but in different context. The next frame of reference uses an integrated binocular signal from the two eyes together with their movements to provide an egocentric frame of reference, the coordinate origin of which lies between the eyes. We perceive the directions of objects with respect to the egocentric. Visual direction alone would not enable us to locate objects in space; in order to do this we also need to determine the distance objects are away from us along the line of visual direction. (Swanston & Wade, 2001, p. 217) There are many sources of information for the relative distances between objects-which is nearer or further-but these need to be anchored by information for egocentric distance before objects can be adequately located in space. If information for the observer’s own movement is incorporated, then objects can be represented in the geocentric frame of reference. When we have derived a geocentric representation of objects, we are in a position to behave appropriately with respect to them. The projections from the ear to the brain follow the same broad principles as visual perceptions but the implementation is more complex and intricate. There are more relays before and in the midbrain, and more crossovers between hemispheres mediated by these relays. (Broerse, 1999, p3.27) Perception gives rise to perceptual constancy, the fact that we normally perceive objects as having constant characteristics, like size, shape, or colour, even when there are changes in the information about these characteristics that reaches the eye. However, the issue is really broader than is implied by this definition. A fundamental requirement for perception is that both the changing and constant characteristics of the environment should be accurately represented. This has to be accomplished despite changes in the pattern of stimulation reaching the eye due to an observer’s own activities. We can perceive that objects with a constant physical size are not changing in size when we move towards or away from them or they move towards or away from us, and we can perceive an object’s shape correctly even if it is seen from different directions. In hearing, all is done through frequency and pitch, which is influenced by loudness. Without such abilities, recognition and identification would be impossible, as there would be no consistent description of an object to remember and make use of on subsequent occasions. Vision is about perception of a pitch in the absence of a missing fundamental that emerges at higher stages of auditory processing in the brain such as visual information or hearing information. The assumption underlying this is that knowledge about what things should look like or sound like must occur at these higher stages of brain processing. This refers to the point that perception theory whether it is about vision or decision cannot be judged without the active participation of brain processing, which means that it is all about how the brain processes our visions that in turn enable us to take decisions. References & Bibliography Broerse Jack, (1999) “Sensory Systems” In Psychological Science: An Introduction Gordon E. Ian, (2004) Theories of Visual Perception: Psychology Press: Hove, England. Gordon Haim & Tamari Shlomit, (2004) Maurice Merleau-Ponty’s Phenomenology of Perception: A Basis for Sharing the Earth: Praeger: Westport, CT. Matthen Mohan, (2005) Seeing, Doing, and Knowing: A Philosophical Theory of Sense Perception: Oxford University Press: Oxford, England. Rookes Paul & Willson Jane, (2000) Perception: Theory, Development, and Organisation: Routledge: London. Swanston T. Michael & Wade J. Nicholas, (2001) Visual Perception: An Introduction: Psychology Press: London. Read More