![]() ![]() His theory of perception is called Top-Down, Which means we use activated conceptual schemas and memory networks (our stored knowledge), more or less automatically and subconsciously, to shape our perceptions or to interpret our sensory input ― sometimes correctly and sometimes not. Gregory proposes that we use our prior “experience of the world to shape how we perceive” stimuli we encounter in it. ![]() A PPT presentation retrieved at Used here with the author’s written permission. It allows us to work out the 3D environment from a non-egocentric point-of-view. A full 3D description of our spatial environment involving the identification of the structure of objects and materials in our visual field. Slide arrangement by Vessels, 2005.ĩ 2½ D Sketch: Depth Cues We perceive much information from which we infer depth: Binocular disparity Texture gradients Occlusion Convergence Relative Size Source: Bell, Vaughan (2004). Rather, just an estimate of the spatial locations of objects and materials in relation to the viewer. Marr called this stage the 2❝ Sketch to emphasis that this stage does not give a full 3D representation. Slide arrangement by Vessels, 2005.Ĩ Stage 3: 2❝ Sketch After gaining information about groupings and surfaces, the viewer needs some spatial information. ![]() The Gestalt Psychologists of the early 19th Century demonstrated many different ways in which we can group objects. Slide arrangement by Vessels, 2005.Īfter the Raw Primal Sketch… Marr … we create a Complete Primal Sketch by grouping surfaces and common areas. This involves the extraction of information regarding edges and intensity changes. Marr proposed there were distinct stages of processing in visual perception: Stage 1: Raw Primal Sketch Stage 2: Complete Primal Sketch Stage 3: 2❝ Sketch Stage 4: Full 3D Representation Source: Bell, Vaughan (2004). He took an information processing view of the mind… …and aimed to describe perception in terms of computations on sense data… …to extract high level visual experience. …he wanted to link neurophysiology with psychology. ![]() Marr wanted to understand mechanisms of vision rather than just behaviors associated with it. Gordon Vessels 2005Ĥ David Marr’s Computational Bottom-Up Approach Perception Stimuli Processing Stimuli Input Created by Dr. What is in this picture? Modeled after a PPT slide created by Kevin Richardson in 1998 and made available through the American Psychological Societyģ Bottom-Up Processing Perception Stimuli Input Stimuli Processing Top-Down Processing Relies on higher-level information such as prior knowledge and experience. Gordon Vessels 2005īottom-Up Processing Relies on properties of the stimulus such as patterns of light and dark areas. Information available in the stimulus itself. Bottom-up Perceive the individual parts and organize them into a whole, if possible. Quick and highly inferential but also a source of misperception. Experience-driven as opposed to stimulus or input-data driven. Perceive the whole and then individual parts as needed. ![]()
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