Chapter 3: Perception Summary This chapter introduces the field of perception: the process by which sensory information is processed to create our conscious experiences of the environment and to guide our actions. Because it is our most dominant sense and because it dominates the field of perceptual research, visual perception is the focal point of this chapter’s treatment of perceptual processes. Perceptual processes are often divided into two major, complementary types of processing: bottom-up (data- driven) processing and top-down (user-driven) processing. Bottom-up processing refers to the contribution of the physical features of the stimulus to our perceptual experience. A great deal of bottom-up theories arose from pattern recognition , which itself was based on two theories: template matching (multiple-trace memory model, Posner experiments) and feature detection (pandemonium model). Biederman offered yet another theory, known as the recognition-by-components theory (RBC), which explains how we rapidly recognize objects based on their constituent, basic, 3-dimensional elements ( geons ). Treisman developed yet another theory ( feature integration theory ), which maintains that objects are first processed preattentively, then attentively. Top-down processing , on the other hand, relates to perception that is influenced by goals, expectation, ns and prior knowledge. The ‘ word superiority effect ’ is a prototypical example of this type of processing. Connectionist models (parallel distributed processing) also support effects of context on perception, as do phenomena such as the ‘ jumbled word effect ’, change blindness (Levin et al. experiments), or filling-in (perceptual completion). Top-down processing is not only limited to semantic effects, it also impacts colour vision. According to the empirical theory of colour vision , we use prior knowledge of how objects look under certain lighting, as well as bottom-up processing in order to perceive colour. Aside from bottom-up and top-down hypotheses, Gestalt psychology was also an influential perspective on the topic of perception processing. The Gestalt approach emphasizes that ‘the whole that is perceived is greater than the sum of its parts’ and illustrated this idea with the use of perceptually bi-stable images . Gestalt psychology’s most influential principle maintained that people have a tendency to group items so as to form the simplest arrangements ( Prägnanz ). 1
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- Winter '08