Sensations Perception Midterm 3 Ch 4a 4b 5b 6 Terms identity or structure Chapter 4a Middle Vision Ambiguous Figure a visual stimulus that vies rise to two or more interpretations of its o In a way all images are inherently ambiguous Any 2D image can have an infinite number of 3D interpretations o Ambiguous figure is usually obviously ambiguous Middle Vision a loosely defined stage of visual processing that comes after basic features have been extracted from the image and before object recognition and scene understanding o Involves the perception of edges and surfaces o Determines which regions of an image should be grouped together into objects High Level Vision another loosely defined stage that comes involves complex image analysis inducing 3D vision object recognition scene understanding and more Extrastriate Cortex region of cortex bordering the primary visual cortex and containing multiple areas involved in visual processing o V2 V3 V4 etc Where pathway concerned with locations of objects but not their names or functions What pathway is concerned with names and functions of objects regardless of location Structuralism a school of thought believing that complex objects or perceptions could be understood by the analysis of components o Developed by Wilhelm Wundt and mentee Edward Tichener Gestalt Psychology The whole is greater than the sum of its parts Gestalt Grouping Rules a set of rules describing which elements in an image will appear to group together Similarity a Gestalt grouping rule stating that the tendency of two features to group together will increase as the similarity between them increases Proximity a Gestalt grouping rule stating that the tendency of two features to group together will increase as the distance between them decreases Good Continuation a Gestalt grouping rule stating that two elements will tend to group together if they lie on the same contour Parallelism parallel contours are likely to belong to the same figure a rule for figure Symmetry symmetrical regions are more likely to be seen as figure a rule for figure Common Region two features will group if they appear to be part of the same larger ground assignment ground region Connectedness Two items will tend to group if they are connected Dynamic Grouping Principles o Common Fate Elements that move in the same direction tend to group together o Synchrony elements that change at the same time tend to group together Camouflage an organism s attempt at breaking Gestalt rules so that its features are not perceived as an object on their own but as parts of a larger object Figure Ground Assignment the process of determining that some regions of an image belong to a foreground object figure and other regions are part of the background ground Global Superiority Effect forest before the trees the properties of the whole object take precedence over the properties of parts of the object Accidental Viewpoint a viewing position that produces some regularity in the visual image that is not present in the world Nonaccidental Feature a feature of an object that is not dependent on the exact or accidental viewing position of the observer Heuristic a mental shortcut Texture Segmentation carving an image into regions of common texture properties Gestalt Figure Ground Assignment Principles Surroundedness if one region is entirely surrounded by another it is likely that the surrounded region is the figure Size The smaller region is more likely to be seen as a figure Symmetry A symmetrical region tends to be seen as figure Parallelism Regions with parallel contours tend to be seen as figure Ideas From Slides Structuralism a school of thought believing that complex objects could be understood by the analysis of the components o The tendency of the visual system to make inferential leaps was problematic for o Argue that perceptions are the sum of atoms of sensations bits of color them orientation and so forth Receptive fields for cells in extrastriate areas are more sophisticated than those in striate cortex o They respond to visual properties important for perceiving objects Ex boundary ownership for a given boundary which side is part of the object and which side is part of the background o A set of rules that describe when elements in an image will appear to group o Patterns are spontaneously organized by the brain into the simplest possible Gestalt Grouping Rules together configurations Gestalt Psychology o Whole is greater than sum of its parts o Gestalt In German form or whole o Wertheimer Kohler Koffka o Opposed to other schools of thought such as structuralism o Most enduring contribution to begin the description of a set of organizing principles that describe the visual system s interpretation of the raw retinal image These rules reflect regularities in the world Context is important Chapter 4b Object Recognition Terms Extrastriate Cortex region of cortex bordering the primary visual cortex and containing multiple areas involved in visual processing o V2 V3 V4 etc What System object identification o Inferior Temporal IT Cortex o Ventral Pathway Where How System object localization manipulation o Parietal Cortex o Dorsal Pathway Middle Vision a loosely defined stage of visual processing that comes after basic features have been extracted from the image and before object recognition and scene understanding o Involves the perception of edges and surfaces o Determines which regions of an image should be grouped together into High Level Vision another loosely defined stage that involves complex image objects analysis o Includes 3D vision object recognition scene understanding and more Na ve Template Theory proposal that the visual system recognizes objects by matching the neural representation of the image with a stored representation of the same shape in the brain o Maintain a memory of many different views for each object we need to recognize Structural Description Theory a description of an object in terms of the nature of its constituent parts and the relationships between those parts o Exploit those properties that can distinguish most objects from on another yet remain relatively stable over changes in views Types of Agnosia General Agnosia inability to recognize objects Prosopagnosia inability to recognize faces Hemispatial Neglect ignore one side of space Inanimate Agnosia inability to recognize inanimate objects Place Agnosia inability to recognize places Mirror Agnosia inability to understand mirrors