6 Perceptual Organization How do we form meaningful perceptions from sensory information? We organize it. Gestalt psychologists showed that a figure formed a gestalt, a “whole” different than its surroundings.
7 Figure-ground is the organization of the visual field into objects (figures) that stand out from their surroundings (ground). In this image, the figure- ground relationship is constantly changing. Form Perception
8 Grouping After distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using grouping rules.
9 Grouping Principles Although grouping principles usually help us construct reality, they may occasionally lead us astray.
10 Depth Perception Visual Cliff Depth 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.
11 Binocular Cues Binocular cues are depth cues that depend on the use of two eyes. One binocular cue is retinal disparity: Images from the two eyes differ. Try looking at both index fingers pointing them towards each other half an inch apart and 5 inches in front of your eyes. You will see a “finger sausage”.
12 Monocular Cues Monocular cues are depth cues available to either eye alone. This figure illustrates interposition, when one object partially blocks our view of another we perceive it as closer.
13 Monocular Cues For examples of these other monocular cues see Fig on page 221. Relative Height: We perceive objects that are higher in our field of vision to be farther away than those that are lower. Relative 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.
14 Monocular Cues Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance. Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away.
15 Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal images change.
Shape constancy is our tendency to perceive the form of familiar objects as constant, even when while our retinal image of it changes, like the door below. 16 Shape Constancy
17 Size-Distance Relationship The distant monster (below, left) and the top red bar (below, right) appear bigger because of distance cues.
18 Size-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. Ames Illusion
19 Lightness Constancy The color and brightness of square A and B are the same. Courtesy Edward Adelson Light constancy: we perceive an object as having a constant lightness even while its illumination varies. This depends on relative luminance – the amount of light an object reflects relative to it’s surroundings.
20 Color constancy is perceiving familiar objects as having consistent color even when changing illumination filters the light reflected by the object. Color Constancy Color depends on context. These 3 blue dots are all the same color.
21 Perceptual Interpretation Immanuel Kant ( ) maintained that knowledge comes from our inborn ways of organizing sensory experiences. John Locke ( ) argued that we learn to perceive the world through our experiences. How important is experience in shaping our perceptual interpretation?
22 Sensory Deprivation & Restored Vision After cataract surgery, blind adults were able to regain sight. These individuals could differentiate figure and ground relationships proving that this is innate, yet they could not visually recognize objects that were familiar by touch.
23 Facial Recognition After blind adults regained sight, they were able to recognize distinct features, but were unable to recognize faces. Normal observers also show difficulty in facial recognition when the lower half of the pictures are changed. Courtesy of Richard LeGrand
24 Perceptual Adaptation Perceptual adaptation is the visual ability to adjust to an artificially displaced visual field, e.g., prism glasses.
25 Perceptual Set A perceptual set is a mental predisposition to perceive one thing and not another. What you see in the center picture is influenced by flanking pictures. From Shepard, 1990.
26 (a) Loch ness monster or a tree trunk; (b) Flying saucers or clouds? Perceptual Set Other examples of perceptual set.
27 Is the “magician cabinet” on the floor or hanging from the ceiling? Context Effects Context can radically alter perception.
28 To an East African, the woman sitting is balancing a metal box on her head, while the family is sitting under a tree. Cultural Context Context instilled by culture also alters perception.
29 Perception is a Biopsychosocial Phenomenon Is perception innate or learned? The answer is both.
30 Extrasensory Perception Perception without sensory input is called extrasensory perception (ESP). This includes, telepathy, clairvoyance, and precognition. A large percentage of scientists do not believe in ESP. Parapsychology is the study of paranormal phenomena, including ESP.