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Fig5_14

InRev5a InRev4bInRev2a PRINCIPLES OF PERCEPTUAL ORGANIZATION AND CONSTANCY Certain objects or sounds are automatically identified as figures, whereas others become meaningless background. Properties of stimuli lead us to automatically group them together. These include proximity, similarity, continuity, closure, texture, simplicity, common fate, and common region. Knowing an object’s two-dimensional position (left and right, up and down) and distance enables us to locate it. The image on the retina and the orientation of the head position provide information about the two-dimensional position of visual stimuli; auditory localization relies on differences in the information received by the ears. Depth or distance perception uses stimulus cues such as occlusion, relative size, texture gradients, linear perspective, clarity, color, and shadow. Objects are perceived as constant in size, shape, color, and other properties, despite changes in their retinal images. Principle Figure-ground processing Grouping (Gestalt laws) Perception of location and depth Perceptual constancy You see a person standing against a building, not a building with a person- shaped hole in it. People who are sitting together, or are dressed similarly, are perceived as a group. Large, clear objects appear closer than small, hazy objects. A train coming toward you is perceived as getting closer, not larger; a restaurant sign is perceived as rotating, not changing shape. DescriptionExample

05_18 Presented stimulus Features detected Features combined Patterns recognized

InRev5b InRev5aInRev4bInRev2a MECHANISMS OF PATTERN RECOGNITION Raw sensations from the eye or the ear are analyzed into basic features, such as color or movement; these features are then recombined at higher brain centers, where they are compared to stored information about objects or sounds. Knowledge of the world and experience in perceiving allow people to make inferences about the identity of stimuli, even when the quality of raw sensory information is low. Recognition depends on communication among feature- analysis systems operating simultaneously and enlightened by past experience. Mechanism Bottom-up processing Top-down processing Network, or PDP, processing You recognize a dog as a dog because its physical features— four legs, barking, panting— match your perceptual category for “dog.” On a dark night, a small, vaguely seen blob pulling on the end of a leash is recognized as a dog because the stimulus occurs at a location where we would expect a dog to be. A dog standing behind a picket fence will be recognized even though each disjointed “slice” of the stimulus may not look like a dog. DescriptionExample

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InRev5c InRev5bInRev5aInRev4bInRev2a ATTENTION Directs sensory and perceptual systems toward stimuli Selects specific information for further processing Allocates mental energy to process information Regulates the flow of resources necessary for performing a task or coordinating multiple tasks Characteristics Improves mental functioning Requires effort Has limits Overt orienting (e.g., cupping your ear to hear a whisper) Covert orienting (e.g., thinking about spring break while looking at the notes in front of you) Voluntary control (e.g., purposefully looking for cars before crossing a street) Involuntary control (e.g., losing your train of thought when you’re interrupted by a thunderclap) Automatic processing (e.g., no longer thinking about grammar rules as you become fluent in a foreign language) Divided attention (e.g., looking for an open teammate while you dribble a soccer ball down the field) FunctionsMechanisms

L5 SOCIAL COGNITION Can subliminal stimuli influence our judgments about people? (p. 624) HUMAN DEVELOPMENT What does the world look like to infants? (p. 163) SENSATION How can the senses be fooled? (p. 154) LINKAGES to Perception