Perception and sensation play an important role in cognition and understanding of the world. There are many aspects to a perception (binocular parallax, motion parallax, etc.). It must be the case that a substantial amount of perception is dependent on past experience and learning. This is true in so far as there is a vague dividing line between what is perception and what is general knowledge about the world. Regarding innate behaviour, when interpreting findings and trying to think of new ideas for experiments, it is often useful to think of the survival value of such behavior. During sensation, covert stimuli are assumed to function as do overt stimuli. Just as an overt stimulus can occur and fail to be discriminated, so a covert stimulus may occur without its being discriminated (Blake and Sekuler 2005). Therefore, for the occurrence of a sensation or an awareness of a feeling, it is necessary that a discriminative response occur in addition to the covert stimulus. In contrast, according to the neural identity theory, the occurrence of the brain state is sufficient for the occurrence of the sensation or feeling.
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“Some philosophers wish to treat perception simply as the acquisition of beliefs, so that perceptual content is not essentially different from purely conceptual content” (). The perception of depth obviously has some kind of general survival value. For example, if the baby can perceive a precipice, then she is better. perhaps from birth, or at least from a very early age, critics might find individuals show some kind of defensive reaction to an object that is heading towards them on a collision course. Such reaction, if it minimized harm, would be of great benefit to the individuals health and safety. Another aspect of perceptual organization that could be present from birth is the rule of 'good continuation'. This means that if we see one object partly covering another, we assume that the contours of the partly hidden object that are out of view continue in much the same way as those in view. For example, if we see a painting hanging on the wall, we may automatically assume that the pattern of the wallpaper continues behind the painting just as it does all around the painting. Of course, it could be that this assumption is wrong, and that in fact the painting is strategically placed to hide a hole in the wall. Nevertheless, unless we happen to be a property surveyor, it is highly unlikely that we would be suspicious in this way. Our default assumption seems to be that the pattern is a continuous one, carrying on behind the painting (Blake and Sekuler 2005).
In sensation, greater number senses take place in world understanding. The relationship between the brain state and the first-person report is left unclear. covert stimuli are assumed to function as do overt stimuli. Just as an overt stimulus can occur and fail to be discriminated, so a covert stimulus may occur without its being discriminated. Therefore, for the occurrence of a sensation or an awareness of a feeling, it is necessary that a discriminative response occur in addition to the covert stimulus. In contrast, according to the neural identity theory, the occurrence of the brain state is sufficient for the occurrence of the sensation or feeling (Wolfe et al. 2008). The remaining relationship between the brain state and the first-person report is left unclear. From this second difference between the two views, a third immediately follows. Since under the hypothetical-construct interpretation a discriminative response is necessary for the having of a sensation and yet can take any number of forms, depending on the subject's learning history, the physiological processes which mediate the having of a sensation or feeling can be identified only functionally--that is, by the role they play--rather than anatomically (Merlean-Ponty, 2002).
For instance, in perception, the bar-triangle figure has figure-ground properties. That is, as we focus on the bar, so the triangle becomes background to that figure. Another way of saying this is that the bar-triangle figure does not appear as just a pattern, but as one object in front of another. Bower's experiment suggests figure-ground perception is innate, for the reasons given in the preceding paragraph. There is evidence suggesting the same coming from studies on people who had been blind from birth, but then had vision repaired as adults. These are cases of people who had eye cataract problems, but who did not have an operation to remedy the problem until they were adult because the surgical technology had not been available sooner. . Alternatively, it might be that babies have no such problem, and that adults with restored vision have special difficulties arising through lack of use of the parts of the brain involved in visual perception. If we left a car standing for twenty years it would be a very optimistic person who would expect to get in and drive away without problems. The lack of use and attention the car suffered would cause deterioration. So we could expect the same with parts of the brain not used for such a long time. This lack of use must have been at least partly responsible for the difficulty repaired-vision patients experience. The newborn is capable of figure-ground perception, and perception of depth by other means, such as by expansion of the image of an object. The newborn appears to have the rudiments for a perception of faces, in the attraction that eyes hold for them. Young babies seem capable of size constancy, recognizing that an object is the same size, even though its retinal image changes with distance (Wolfe et al. 2008). They also seem to recognize an object as the same one, despite changes in orientation. In sum, the baby is equipped with a considerable range of basic perceptual abilities, which provides her with a potential to make sense of what she can see from a very early age. Features of this environment, and one's particular experiences of it, could have an important bearing on some aspects of perception. There can be no doubt that much of the detail that we are able to perceive is dependent on our knowledge base, and therefore on our learning. Gregory's argument about the carpentered environment illustrates this point neatly. We can see, then, that being able to perceive as we do is influenced in a substantial way by both genetic and environmental factors ((Wolfe et al. 2008).
One possibility is that in reporting one's own dispositional state, one is discriminating the environmental independent variables which determine the value of the intervening variable. For example, to state "I am hungry" is to respond discriminatively to features of the environment such as number of hours of deprivation. Alternatively, the report may be a discriminative response to the dependent variables of the intervening variable--i.e., the overt behaviors which are the "realization" of the intervening variable. For example, "I am hungry" is possibly a discriminative response to the overt behaviors which change as the value of the hunger-intervening-variable changes. One important kind of psychological measurement is psychophysical scaling, in which first-person reports are used to measure "sensations" or "sensory magnitudes." On a traditional interpretation, it is assumed that a distal stimulus such as a tone produces certain sensations in the subject who then judges the sensation and reports its magnitude. From judgments of this sort, psychological scales such as "loudness" are derived. Loudness does not correspond to the physical dimensions of the tone, such as its intensity and frequency, and is often conceptualized as a dimension of the sensation rather than of the tone. Possible that lawful relationships can be found between the subject's judgments and certain aspects of covert stimuli, or neural firing, for which rules of measurement are defined. For example, the subject's judgments may be related to the frequency of neural firing, a dimension for which rules of measurement are defined. However, these relationships are psychophysical functions, not rules of measurement (Vision, 1997).
In sum, sensation and perception are based on similar cognitive processes but differ in complexity of senses. The knowledge of what the subject is reporting about in subjective reports is represented by the quality space constructed from the subject's behavior. It seems, however, that this knowledge is deficient in that it is knowledge only about relationships among situations. It does not concern itself with their inherent nature, which accounts for their relating in the ways described by the quality space. This objection distinguishes between knowledge as absolute knowledge of relations.