1. Perceptual Organization Unit 3 – RG 4e Modified PowerPoint from: Aneeq Ahmad -- Henderson State University. Worth Publishers © 2007

2. Perceptual Illusions To understand how perception is organized, illusions provide good examples. It is as good to study faulty perception as other perceptual phenomena. Line AB is longer than line BC.

3. Tall Arch Vertical dimension of the arch looks longer than the horizontal dimension when both are equal. Rick Friedman/ Black Star

4. 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 psychology helps us organize information into meaningful wholes… but remember…the “whole is different from the sum of it’s parts”

5. Figure-Ground Organization of the visual field into objects (figures) that stand out from their surroundings (ground). Time Savings Suggestion, © 2003 Roger Sheperd.

6. Gestalt Grouping Having discriminated figure from ground our perception needs to organize figure into meaningful form using grouping rules.

7. 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

8. Depth Perception 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. Visual Cliff Innervision s

9. 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.

10. 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.

11. Monocular Cues Relative Size: If two objects are similar in size, we perceive one that casts a smaller retinal image as farther away.

12. Monocular Cues Relative Height: We perceive objects higher in our field of vision as farther away. Image courtesy of Shaun P. Vecera, Ph. D., adapted from stimuli that appered in Vecrera et al., 2002

13. Monocular Cues Texture Gradient: Indistinct (fine) texture signals increasing distance. © Eric Lessing/ Art Resource, NY

14. Binocular Cues Convergence: When two eyes move inward (towards the nose) to see near objects, and outward (away from the nose) to see far away objects…object is perceived as closer the more eyes turn inward

15. Binocular Cues Retinal disparity: Images from the two eyes differ…the greater the difference between the two objects, the closer the object 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.

16. Perception of Movement Stroboscopic motion: our tendency to perceive motion in a series of slightly varied still images flashed in rapid succession

17. Perception of Movement Phi Phenomenon: When lights flash at certain speed they tend to present illusions of motion. Neon signs use this principle to create motion perception. Two lights flashing one after the other. One light jumping from one point to another: Illusion of motion.

18. Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal image change. Perceptual constancies include constancies of shape and size. Shape Constancy

19. Size Constancy Stable size perception amid changing size of the stimuli. Size Constancy

20. Size-Distance Relationship Moon Illusion What makes this happen? Cues to the objects’ distances at the horizon make the Moon behind them seem farther away than the moon in the night’s sky. Actually…there are various explanations, yet no ONE “right” answer

21. Size-Distance Relationship The distant monster and the top red bar appear bigger because of distance cues. Ponzo Illusion From Shepard, 1990 Alan Choisnet/ The Image Bank

22. Depth Perception Webquest 1. Go to class website, under Unit 4, Perceptual Organization Notes, click on “Depth Perception Webquest- website” 2. Go through the web page, filling in the chart a quick description of each depth cue 3. Come up with your own example of each depth cue- must be your own, not from the website, book, or notes

23. Size-Distance Relationship Muller-Lyer Illusion Are these vertical lines the same length?

24. 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

25. Ames Room An Ames room is designed to give size-distance illusion.

26. Visual Illusions… Straight lines or bowed? Stationary or moving?

27. Visual Illusions… A spiral right? How many people/faces do you see?

28. Visual Illusions… Which line matches with C? It’s actually B… Poggendorf Illusion Old woman or young woman?

29. Visual Illusions… These are on drawn on flat surfaces (sidewalks)!

30. Visual Illusions… Julian Beever has made pavement drawings for over ten years. He has worked in the U.K., Belgium, France, The Netherlands, Germany, the USA and Australia.

31. Visual Illusions… For more go to… http://users.skynet.be/J.Beever/pave.htm