1. Perception "Colors, tones, smells, and tastes are mental constructions created by the brain out of sensory experience. They do not exist, as such, outside of the brain. " (Martin, 1991). Perception is an active, constructive process* Al Seckel

2. Does perception exist outside of awareness? Subliminality Selective Attention Focus of conscious awareness on a particular stimulus. Cocktail Party Phenomenon Change and Inattentional Blindness djs_lab demos Viewable/Downloadable Examples

3. Perceptual Organization Gestalt Psychology Late 19th/early 20 th field that emphasized the human tendency to organize pieces of information into meaningful patterns or wholes (Max Wertheimer, W. Kohler, F. Koffka) The brain’s tendency to organize sensory stimuli in order to construct reality helps to explain our susceptibility to illusions

4. Gestalt Grouping Principles  The perceptual tendency to organize stimuli into coherent groups (Law of Pragnanz or good order). We tend to order experience in a manner that is regular, orderly, symmetric, and most simple  proximity--group nearby figures together  similarity--group figures that are similar  familiarity—familiar or meaningful pattern  continuity--perceive continuous patterns  closure--fill in gaps  connectedness--spots, lines, and areas are seen as unit when connected  common fate--when objects move in the same direction, we see them as a unit  Gestalt Gestalt

5. Illusory and Subjective Contours- Creating images where they do not exist Kanizsa’s Illusory Triangle

6. Perceptual Organization Among our most basic perceptual tasks is a type of selective attention where we distinguish objects as separate from their surroundings, a concept known as...

7. Infamous Rubin

8. Which picture predominates for you, the younger or older woman?

10. Reversible figures Like with figure ground images in the following illustrations the relationship between the objects continually reverses. Perceptual hypothesis Contends that we bridge the gap between what’s real and what we see by constantly making and testing hypotheses

11. The Necker cube http://dogfeathers.com/java/necker.html

12. Binocular cues Retinal disparity and stereopisis The brain perceives distance and depth by comparing the different images received by each eye Convergence Eyes come together as objects are nearer

13. Stereograms (like 3-D movies) exaggerate retinal disparity by placing two slightly separated images apart. The brain actively reconstructs the images into a 3-D illusion

14. Monocular cues Interposition/Superposition Relative clarity/aerial perspective Texture gradient Relative height Relative size Light and shadow Linear perspective Motion parallax

16. Paris Street: A Rainy Day Gustave Caillebotte

18. Pavement Drawings Julian Beever

19. Illusions you should know (and their possible explanations) Figure-ground Reversible figures (Necker cube) Illusory contours (Kanizsa triangle) Size-distance illusions (Ames Room, Muller-Lyer & Ponzo illusion) Impossible figures (role of perceptual set/schema) Think gestalt…Top down processing (perceptual hypothesis)

20. Size-Distance Illusions In each of these examples, the top and bottom lines are actually the same length. In each case the top line looks longer. Because? Mueller-Lyer Illusion (a) Müller-Lyer illusion

21. Ames Room Monocular depth cues give the illusion that the two people are equally far away AmesAmes

22. The Ponzo Illusion What misassumptions cause this illusion?

23. The monocular cues of linear perspective and relative size are responsible for this illusion. How? Shepard's Terror Subterra

24. More Perception Terms Real vs. apparent movement –Autokinetic effect/illusion –Stroboscopic motion –Phi Phenomenon PHI Phenomenon ActivityPHI Phenomenon Activity –Induced movement (stationary-moon) –Moving Aftereffect (MAE) –spiral aftereffect/waterfall illusion Motion AftereffectMotion Aftereffect –Motion induced blindness (VSR) MIBMIB YTMIB

25. Motion Illusions Freezing Rotation Illusion Motion Induced Blindness “Stepping feet” Motion Illusion Stereokinetic Phenomenon Motion-Bounce Illusion

26. Perceptual Constancy Perceiving objects as unchanging even as illumination and retinal image change  color  shape  size

27. Contrast and Color Illusions Grid Illusions: Hering Wertheimer-Koffka-Ring Munker-White Illusion Adelson -- Checker-shadow illusion Lilac Chaser Cool Escher-inspired movie An “impossible” MovieAn “impossible” Movie Beau Lotto

28. The Stroop Effect Stroop found that the act of reading could interfere with your ability to perform simple perceptual distinctions like naming colors Stroop Lab Introduction

29. Other Misleading Cues and Line Illusions Hering Illusion Café Wall Illusion

30. Impossible Figures