3PerceptionThe process of selecting, organizing, and interpreting sensory information, which enables us to recognize meaningful objects and events.
4Selective AttentionPerceptions about objects change from moment to moment. We can perceive different forms of the Necker cube; however, we can only pay attention to one aspect of the object at a time.OBJECTIVE 1| Describe the interplay between attention and perception.Necker Cube
5Inattentional Blindness Inattentional blindness refers to the inability to see an object or a person in our midst. Simmons & Chabris (1999) showed that half of the observers failed to see the gorilla-suited assistant in a ball passing game.Daniel Simons, University of Illinois
7Perceptual IllusionsIllusions provide good examples in understanding how perception is organized. Studying faulty perception is as important as studying other perceptual phenomena.OBJECTIVE 2| Explain how illusions help us understand some of the ways we organize stimuli into meaningful perceptions.Line AB is longer than line BC.
113-D IllusionReprinted with kind permission of Elsevier Science-NL. Adapted fromHoffman, D. & Richards, W. Parts of recognition. Cognition, 63, 29-78It takes a great deal of effort to perceive this figure in two dimensions.
12Perceptual Organization When vision competes with our other senses, vision usually wins – a phenomena called visual capture.OBJECTIVE 3| Describe Gestalt psychology's contribution to our understanding of perception.
13Gestalt PsychologyAt the beginning of the 20th century, a group of researchers called Gestalt psychologists described principles on how we perceive groups of objects.Gestalt is a German word meaning “form” or “whole.”Gestalt Psychologists would say “the whole may exceed the sum of its parts.” In other words, we organize our sensations into a “whole” different from its surroundings.
17Depth PerceptionDepth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception.OBJECTIVE 5| Explain the importance of depth perception, and discuss the contribution of visual cliff research to our understanding of this ability.InnervisionsVisual Cliff
18Binocular CuesRetinal disparity: Images from the two eyes differ. Try looking at your two index fingers when pointing them towards each other half an inch apart and about 5 inches directly in front of your eyes. You will see a “finger sausage” as shown in the inset.
19Binocular CuesConvergence: Neuromuscular cues. When two eyes move inward (towards the nose) to see near objects and outward (away from the nose) to see faraway objects.OBJECTIVE 6| Describe two binocular cues for perceiving depth, and explain how they help the brain to compute distance.
21Monocular CuesRelative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away.OBJECTIVE 7| Explain how monocular cues differ from binocular cues, and describe several monocular cues for perceiving depth.
22Monocular CuesInterposition: Objects that occlude (block) other objects tend to be perceived as closer.Rene Magritte, The Blank Signature, oil on canvas,National Gallery of Art, Washington. Collection ofMr. and Mrs. Paul Mellon. Photo by Richard Carafelli.
23Monocular CuesRelative Clarity: Because light from distant objects passes through more light than closer objects, we perceive hazy objects to be farther away than those objects that appear sharp and clear.
26Monocular CuesRelative Height: We perceive objects that are higher in our field of vision to be farther away than those that are lower.Image courtesy of Shaun P. Vecera, Ph. D.,adapted from stimuli that appered in Vecrera et al., 2002
27Monocular CuesRelative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction.
30Motion PerceptionMotion Perception: Objects traveling towards us grow in size and those moving away shrink in size. The same is true when the observer moves to or from an object.OBJECTIVE 8| State the basic assumption we make in our perceptions of motion, and explain how these perceptions can be deceiving.
31Apparent MotionPhi Phenomenon: When lights flash at a certain speed they tend to present illusions of motion. Neon signs use this principle to create motion perception.One light jumping from one point to another: Illusion of motion.Two lights flashing one after the other.
32Perceptual ConstancyPerceiving objects as unchanging even as illumination and retinal images change. Perceptual constancies include constancies of shape and size.OBJECTIVE 9| Explain the importance of perceptual constancy.Shape Constancy
33Stable size perception amid changing size of the stimuli. Size ConstancyStable size perception amid changing size of the stimuli.OBJECTIVE 10| Describe the shape and size constancy, and explain how our expectations about perceived size and distance to some visual illusions.Size Constancy
34Size-Distance Relationship The distant monster (below, left) and the top red bar (below, right) appear bigger because of distance cues.Alan Choisnet/ The Image BankFrom Shepard, 1990
35Size-Distance Relationship Both girls in the room are of similar height. However, we perceive them to be of different heights as they stand in the two corners of the room.Both photos from S. Schwartzenberg/ The Exploratorium
36The Ames room is designed to demonstrate the size-distance illusion.
37The color and brightness of square A and B are the same. Lightness ConstancyOBJECTIVE 11| Discuss lightness constancy and its similarity to color constancy.Courtesy Edward AdelsonThe color and brightness of square A and B are the same.
38Color ConstancyPerceiving familiar objects as having consistent color even when changing illumination filters the light reflected by the object.Color Constancy