Perceptual Organization Illusions Gestalt organization Depth perception Binocular cues of vision (2) Monocular cues of vision (8) Feature extraction Motion perception Constancy Psychology 7e in Modules

Perceptual Organization When vision competes with other senses vision usually wins – a phenomenon called visual capture. How do we form meaningful perceptions from sensory information? We organize it. “Gestalt” psychologists showed that a figure forms a “whole” different than its surroundings. OBJECTIVE 16-2| Describe Gestalt psychology's contribution to our understanding of perception. Psychology 7e in Modules

Perceptual Illusions To understand how perception is organized, illusions provide good examples. It is as good to study faulty perception as other perceptual phenomena. OBJECTIVE 16-1| Explain how illusions help us understand some of the ways we organize stimuli into meaningful perceptions. The Muller-Lyer illusion Line AB is longer than line BC. Psychology 7e in Modules

More Muller-Lyer illusions

Poggendorf Illusion involves the misperception of the position of one segment of a transverse line that has been interrupted by the contour of an intervening structure (here a rectangle) acute angles in the figure are seen by viewers as expanded though the illusion diminishes or disappears when the transverse line is horizontal or vertical.

Tall Arch Rick Friedman/ Black Star Vertical dimension of the arch looks longer than the horizontal dimension when both are equal. Psychology 7e in Modules

Illusion of a Worm © 1981, by permission of Christoph Redies and Lothar Spillmann and Pion Limited, London Figure on the right gives us the illusion of a blue hazy “worm” when it is nothing else but blue lines identical to the picture on the left. Psychology 7e in Modules

3-D Illusion Reprinted with kind permission of Elsevier Science-NL. Adapted from Hoffman, D. & Richards, W. Parts of recognition. Cognition, 63, 29-78 To perceive this figure in two dimensions takes a great deal of effort. Psychology 7e in Modules

This is a “figure-ground” relationship Form Perception Organization of the visual field into objects (figures) that stand out from their surroundings (ground). OBJECTIVE 16-3| Explain the figure-ground relationship and identify principles of perceptual grouping in form perception. This is a “figure-ground” relationship Psychology 7e in Modules

M.C. Escher--Night & Day

Grouping according to Gestalt Having discriminated figure from ground our perception needs to organize figure into meaningful form using grouping rules. Psychology 7e in Modules

Grouping & Reality Usually grouping principles help us construct reality but at times lead us astray. Both photos by Walter Wick. Reprinted from GAMES Magazine. .© 1983 PCS Games Limited Partnership Psychology 7e in Modules

Depth Perception Visual Cliff Experiment-Eleanor Gibson Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even new born animals show depth perception. OBJECTIVE 16-4| Explain the importance of depth perception, and discuss the contribution of visual cliff research to our understanding of this ability. Innervisions Visual Cliff Experiment-Eleanor Gibson Psychology 7e in Modules

Binocular Cues (need both eyes working together) Convergence: Neuromuscular cues. Your eyes move together the closer the object is to your face and move away from one another as the objects moves away from your face. OBJECTIVE 16-5| Describe two binocular cues for perceiving depth, and explain how they help the brain to compute distance. Psychology 7e in Modules

Binocular Cues Retinal disparity: Images from the two eyes differ because of the space between them. Try looking at your two fingers half an inch apart about 5 inches away. You will see a “finger sausage” as shown in the inset. The closer the object is to our eyes, the greater the difference between the images we perceive. Psychology 7e in Modules

Monocular Cues Relative Size: If two objects are similar in size, we perceive one that casts a smaller retinal image as farther away. OBJECTIVE 16-6| Explain how monocular cues differ from binocular cues, and describe several monocular cues for perceiving depth. Psychology 7e in Modules

Monocular Cues Interposition: 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 of Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli. Psychology 7e in Modules

Monocular Cues Relative Clarity: Because light from distant objects passes through more air, we perceive hazy objects as farther away than sharp clear objects. Psychology 7e in Modules

Monocular Cues Texture Gradient: Indistinct (fine) texture signals increasing distance. © Eric Lessing/ Art Resource, NY Psychology 7e in Modules

Monocular Cues Relative Height: We perceive objects higher in our field of vision as farther away. This can create the “horizontal-vertical illusion” if viewed with both eyes and can be reduced by closing one eye. Psychology 7e in Modules

Monocular Cues Relative motion: Objects closer to a fixation point move faster and in opposing direction to objects farther away from a fixation point, which move slower and in the same direction. Psychology 7e in Modules

This is the “Ponzo Illusion” Monocular Cues Linear Perspective: Parallel lines like rail road tracks, appear to converge with distance. The more the lines converge, the greater their perceived distance. This is the “Ponzo Illusion” Psychology 7e in Modules

Monocular Cues Light and Shadow: Nearby objects reflect more light to our eyes. Given two identical objects, the dimmer one seems further away. From “Perceiving Shape From Shading” by Vilayaur S. Ramachandran. © 1988 by Scientific American, Inc. All rights reserved. Psychology 7e in Modules

Feature Extraction The identification and analysis of specific elements of a sensory input. Allows for encoding of new info into memory  2 benefits      Helps you identify it Helps compare it to other inputs Depends to some degree on knowing what to look for Motion capture---remember the motion dots in the video (dancing/basketball/fencing???)--link 4 Steps: Detection Pattern dissection Feature comparison in memory Recognition

Motion Perception Motion Perception: Objects that tend to travel towards us grow in size and ones that move away shrink in size. The same is true when the observer moves to or from an object. OBJECTIVE 16-7| State the basic assumption we make in our perceptions of motion, and explain how these perceptions can be deceiving. Psychology 7e in Modules

Apparent Motion Phi Phenomenon: When lights flash at certain speed they tend to present illusions of motion. Neon signs and Christmas chaser lights use this principle to create motion perception.—( lilac chaser link) Stroboscopic Effect: It occurs when the view of a moving object is represented by a series of short samples as distinct from a continuous view (like a flip book) or a wagon wheel spinning—(wagon wheel link), (helicopter link) One light jumping from one point to another: Illusion of motion. Two lights flashing one after the other. Psychology 7e in Modules

Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal image change. Perceptual constancies include constancies of shape and size. OBJECTIVE 16-8| Explain the importance of perceptual constancy. Shape Constancy Psychology 7e in Modules

Stable size perception amid changing size of the stimuli. Size Constancy Stable size perception amid changing size of the stimuli. OBJECTIVE 16-9| Describe the shape and size constancy, and explain how our expectations about perceived size and distance to some visual illusions. Size Constancy Psychology 7e in Modules

Size-Distance Relationship The distant monster and the top red bar appear bigger because of distance cues. Alan Choisnet/ The Image Bank From Shepard, 1990 Psychology 7e in Modules

Horizon Moon

High moon on a clear night.

Size-Distance Relationship Both girls in the room are of similar height, however we perceive them of different heights as they stand in the two corners of the room. Both photos from S. Schwartzenberg/ The Exploratorium Psychology 7e in Modules

An Ames room is designed to give size-distance illusion. Psychology 7e in Modules

The color and brightness of square A and B are the same. Lightness Constancy OBJECTIVE 16-10| Discuss lightness constancy and its similarity to color constancy. Courtesy Edward Adelson The color and brightness of square A and B are the same. Psychology 7e in Modules

Color Constancy Perceiving familiar objects as having consistent color, even if changing illumination filters the light reflected by the object. Color Constancy

Optical illusions you should know Afterimage effect Ames Room Checker-shadow Figure-ground Moon illusion Muller-Lyer Necker cube Phi phenomenon Ponzo illusion Vertical-horizontal (tall arch)

AP info… Why do we “see” illusions? There are 2 binocular cues (you need both eyes)—convergence and retinal disparity There are 8 monocular cues (one eye) interposition, linear perspective, texture gradient, relative size, height, motion, clarity, light/shadow

Perceptual Interpretation Perceptual sets and schemas Context effects ESP Psychology 7e in Modules

Perceptual Interpretation Immanuel Kant (1724-1804) maintained that knowledge comes from our inborn ways of organizing sensory experiences (NATURE). John Locke (1632-1704) argued that through our experiences we also learn to perceive the world (NURTURE). How important is experience in shaping our perceptual interpretation?

Top-Down Processing We perceive by filling the gaps in what we sense. I _ant ch_co_ate ic_ cr_am. Based on our experiences and schemas. If you see many old men in glasses, you are more apt to process a picture of an old man (even when you may be in error).

Restored Vision After cataract surgery blind adults were able to regain sight. These individuals could differentiate figure and ground relationship however had difficulty discriminating a circle and a triangle (Von Senden, 1932). OBJECTIVE 17-1| Describe the contribution of restored-vision and sensory deprivation research in our understanding of the nature-nurture interplay in our perceptions. Psychology 7e in Modules

Facial Recognition After blind adults were able to regain sight they were unable to recognize faces, they would only recognize distinct features. Normal observers also show difficulty in facial recognition when lower half of the pictures are changed. Courtesy of Richard LeGrand Psychology 7e in Modules

Perceptual Set A mental predisposition to perceive one thing and not another. What you see in the center picture is influenced by flanking pictures. OBJECTIVE 17-3| Define perceptual set, and explain how it influences what we do or do not perceive. Right half of the class should close their eyes and the left half of the class should see the saxophonist for about 20 seconds. Then the left half of the class should close the eyes and the right half should see the woman’s face. All of them should then write their responses while watching the middle picture. Responses are compared to show perceptual set. From Shepard, 1990. Psychology 7e in Modules

Perceptual set and Auditory perception 1970’s and 1980’s several groups accused recording artists of inserting satanic messages within songs. The message could be heard if the track was played backward (“backmasking”) This is different than “phonetic reversal” Ask yourself how does your expectancy affect what you perceive…here are some examples…

Perceptual Set Other examples of perceptual set. Frank Searle, photo Adams/ Corbis-Sygma Dick Ruhl (a) Loch ness monster or a tree trunk; (b) Flying Saucers or Clouds? Psychology 7e in Modules

Schemas Schemas are concepts that organize and interpret unfamiliar information. Courtesy of Anna Elizabeth Voskuil What we perceive not only comes from the environment but also from our minds. Schemas or concepts develop through experience. Children's schemas represent reality as well as their abilities to represent what they see. Psychology 7e in Modules

Eyes and mouth play a dominant role in face recognition. Eye & Mouth Eyes and mouth play a dominant role in face recognition. Portrait artists understood the importance of this recognition and therefore centered an eye in their paintings. Courtesy of Christopher Tyler Psychology 7e in Modules

Context Effects Context can radically alter perception. OBJECTIVE 17-4| Explain why the same stimulus can evoke different perceptions in different contexts. Is the “magician cabinet” on the floor or hanging from the ceiling? Psychology 7e in Modules

Context instilled by culture also alter perception. Cultural Context Context instilled by culture also alter perception. To an East African the sitting woman is balancing a metal box on her head and the family was sitting under a tree. Psychology 7e in Modules

Is perception innate or acquired? Perception Revisited Is perception innate or acquired? Psychology 7e in Modules

Perception & Human Factors Human factors psychologists design machines that assist our natural perceptions. OBJECTIVE 17-5| Describe the role human factors psychologists play in creating user-friendly machines and work settings. Photodisc/ Punchstock Courtesy of General Electric The knobs for the stove burners on the right is easier to understand than one on the left. Psychology 7e in Modules

Is There Extrasensory Perception? Perception without sensory input is called extrasensory perception (ESP). A large percentage of scientists do not believe in ESP. But…. OBJECTIVE 17-6| Identify the three most testable forms of ESP, and explain why most research psychologists remain, skeptical of ESP. Psychology 7e in Modules

Claims of ESP Telepathy: Mind-to mind communication. One person sending thoughts and the other receiving it. Clairvoyance: Perception of remote events. Like sensing a friend’s house on fire. Precognition: Perceiving future events. Such as a political leader’s death. Psychokinesis: The ability to control movement of inanimate objects (Ex. Yuri Geller) Psychology 7e in Modules

Devil’s Tuning Fork

M. C. Escher: Relativity

M. C. Escher: Waterfall

AP info… Gestalt and wanting the “whole picture” What role do schemas play in perception? Expectancy set and perceptual set Experiences Schemas