Cognitive Perception

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Perception definitions


Top down/Bottom up processing

They are strategies of information processing and knowledge ordering. Top down processing is where perceptions are influenced by expectations, experience and existing beliefs. It is conceptually driven and needs context (e.g. bad handwriting easier to understand in full sentences). Gregory 1970 perception is a constructive process which relies on a top down approach. When we look at something we gain a perceptual hypothesis which us based on our prior knowledge and a lot of information reaches the eye but not the brain. The formation of incorrect hypotheses are the reason for errors of perception as a single pattern can create two perceptions. Bottom up processing is directly influenced by environmental stimuli. It goes through a sequence of processing stages from the retina to the visual cortex, analysing the input on the way through. Analysis from raw data. Gibson 1966 direct theory of perception, perception is direct and not subject to hypothesis testing. There is enough information in the environment about size, item, shape and distance. Motion parallax can be used to show bottom up processing as it looks at the way as we move through our environment, closer objects move by faster. However it cannot explain why perceptions are sometimes wrong. Compare to Marr top down model, four stage process of visual image- early stages of visual processing and Biederman top down approach recognition by components through 36 geons.



Marr 1982 proposed a theory looking at different levels for the understanding of visual processing to explain the early stages of the process. The model is comparing the human brain to the way in which a computer works and builds up the image within the brain. The model includes when an object is first seen by the retina and is then built up into a primal sketch of the scene based on feature extraction of fundamental components. A 2.5D sketch is then produced where textures are then acknowledged which then builds into a 3D model where the scene is visible to us in a continuous map. Can be seen as being very influential in later work although his work lacked evidence. Can link to the top down model as textures of the environment built up in the sketches are based on expectations. 


Recognition by components

Biederman 1987 believed there was a process that could be used to explain object recognition. We are able to recognise objects by


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