Perception

PSYCHOLOGY(8th Edition)David MyersPowerPoint SlidesAneeq AhmadHenderson State UniversityWorth Publishers, 20061PerceptionChapter 62PerceptionSelective AttentionPerceptual IllusionsPerceptual Organization Form Perception Motion Perception Perceptual Constancy31

PerceptionPerceptual Interpretation Sensory Deprivation andRestored Vision Perceptual Adaptation Perceptual Set Perception and Human Factor4PerceptionIs there ExtrasensoryPerception? Claims of ESP Premonitions or Pretensions Putting ESP to Experimental Test5PerceptionThe process of selecting, organizing, andinterpreting sensory information, which enables usto recognize meaningful objects and events.62

Selective AttentionPerceptions about objects change from moment tomoment. We can perceive different forms of theNecker cube; however, we can only pay attentionto one aspect of the object at a time.7Necker CubeInattentional BlindnessDaniel Simons, University of IllinoisInattentional blindness refers to the inabilityto see an object or a person in our midst.Simmons & Chabris (1999) showed that halfof the observers failed to see the gorilla‐suited assistant in a ball passing game.8Change BlindnessChange blindness is a form of inattentionalblindness in which two‐thirds of individualsgiving directions failed to notice a change in theindividual asking for directions. 1998 Psychonomic Society Inc. Image provided courtesy of Daniel J. Simmons.93

Perceptual IllusionsIllusions provide good examples inunderstanding how perception is organized.Studying faulty perception is as important asstudying other perceptual phenomena.Line AB is longer than line BC.10Tall ArchRick Friedman/ Black StarIn this picture, thevertical dimensionof the arch lookslonger than thehorizontaldimension.However, both areequal.11Illusion of a Worm 1981, by permission of Christoph Redies andLothar Spillmann and Pion Limited, LondonThe figure on the right gives the illusion of a blue hazy“worm” when it is nothing else but blue lines identicalto the figure on the left.124

3‐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 intwo dimensions.13Perceptual OrganizationWhen vision competes with our other senses,vision usually wins – a phenomena called visualcapture.How do we form meaningful perceptions fromsensory information?We organize it. Gestalt psychologists showed thata figure formed a “whole” different than itssurroundings.14Form PerceptionOrganization of the visual field into objects(figures) that stand out from their surroundings(ground).Time Savings Suggestion, 2003 Roger Sheperd.155

GroupingAfter distinguishing the figure from the ground,our perception needs to organize the figure intoa meaningful form using grouping rules.16Grouping & RealityAlthough grouping principles usually help us constructreality, they may occasionally lead us astray.Both photos by Walter Wick. Reprinted from GAMESMagazine. . 1983 PCS Games Limited Partnership17Depth PerceptionInnervisionsDepth perception enables us to judge distances.Gibson and Walk (1960) suggested that humaninfants (crawling age) have depth perception. Evennewborn animals show depth perception.Visual Cliff186

Binocular CuesRetinal disparity: Images from the two eyes differ. Trylooking at your two index fingers when pointing themtowards each other half an inch apart and about 5 inchesdirectly in front of your eyes. You will see a “fingersausage” as shown in the inset.19Binocular CuesConvergence: Neuromuscular cues. When twoeyes move inward (towards the nose) to see nearobjects and outward (away from the nose) to seefaraway objects.20Monocular CuesRelative Size: If two objects are similar in size, weperceive the one that casts a smaller retinal imageto be farther away.217

Monocular CuesInterposition: Objects that occlude (block) otherobjects 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.22Monocular CuesRelative Clarity: Because light from distant objectspasses through more light than closer objects, weperceive hazy objects to be farther away thanthose objects that appear sharp and clear.23Monocular CuesTexture Gradient: Indistinct (fine) texture signalsan increasing distance. Eric Lessing/ Art Resource, NY248

Monocular CuesRelative Height: We perceive objects that are higher in ourfield 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., 200225Monocular CuesRelative motion: Objects closer to a fixation pointmove faster and in opposing direction to thoseobjects that are farther away from a fixation point,moving slower and in the same direction.26Monocular CuesLinear Perspective: Parallel lines, such as railroadtracks, appear to converge in the distance. Themore the lines converge, the greater theirperceived distance. The New Yorker Collection, 2002, Jack Zieglerfrom cartoonbank.com. All rights reserved.279

Monocular CuesLight and Shadow: Nearby objects reflect more light intoour eyes than more distant objects. Given two identicalobjects, the dimmer one appears to be farther away.From “Perceiving Shape From Shading” by VilayaurS. Ramachandran. 1988 by Scientific American, Inc.All rights reserved.28Motion PerceptionMotion Perception: Objects travelingtowards us grow in size and those movingaway shrink in size. The same is true whenthe observer moves to or from an object.29Apparent MotionPhi Phenomenon: When lights flash at a certainspeed they tend to present illusions of motion.Neon signs use this principle to create motionperception.Two lightsafter the Illusionother. of motion.One light jumpingfrom flashingone pointoneto another:3010

Perceptual ConstancyPerceiving objects as unchanging even asillumination and retinal images change. Perceptualconstancies include constancies of shape and size.Shape Constancy31Size ConstancyStable size perception amid changing size of thestimuli.Size Constancy32Size‐Distance RelationshipThe distant monster (below, left) and the top redbar (below, right) appear bigger because ofdistance cues.Alan Choisnet/ The Image BankFrom Shepard, 19903311

Size‐Distance RelationshipBoth girls in the room are of similar height.However, we perceive them to be of differentheights as they stand in the two corners of theroom.Both photos from S. Schwartzenberg/ The Exploratorium34Ames RoomThe Ames room is designed to demonstrate the size‐distance illusion.35CourtesyEdwardAdelsonLightness ConstancyThe color and brightness of square A and B are the same.3612

Color ConstancyPerceiving familiar objects as having consistentcolor even when changing illumination filtersthe light reflected by the object.3713

Sensory Deprivation and Restored Vision Perceptual Adaptation Perceptual Set Perception and Human Factor 5 Perception Is there Extrasensory Perception? Claims of ESP Premonitions or Pretensions Putting ESP to Experimental Test 6 Perception The process of selecting, organizing, and