The document discusses key concepts in perception including size constancy, shape constancy, brightness constancy, and figure-ground organization. It also covers Gestalt principles of perceptual organization such as similarity, continuity, and closure. Depth perception is discussed including monocular and binocular cues like linear perspective, overlap, and motion parallax. Common illusions are also described such as the moon illusion and Muller-Lyer illusion.

1. Perceiving the World

3. Fig. 6.1 Shape constancy. (a) When a door is open its image actually forms a trapezoid. Shape constancy is indicated by the fact that it is still perceived as a rectangle. (b) With great effort you may be able to see this design as a collection of flat shapes. However, if you maintain shape constancy the distorted squares strongly suggest the surface of a sphere. (From Spherescapes-1 by Scott Walter and Kevin McMahon, 1983.) Table of Contents Exit

5. Fig. 6.2 A reversible figure-ground design. Do you see two faces in profile, or a wineglass? Table of Contents Exit

7. Fig. 6.3 How we organize perceptions Table of Contents Exit

9. Fig. 6.5 A challenging example of perceptual organization. Once the camouflaged insect (known as a giant walkingstick) becomes visible, it is almost impossible to view the picture again without seeing the insect. Table of Contents Exit © E.R. Degginger/Animals Animals

12. Fig. 6.10 The eyes must converge, or turn in toward the nose, to focus close objects. Table of Contents Exit

14. Fig. 6.14 (a) Linear perspective. (b) Relative size. (c) Light and shadow. (d) Overlap. (e) Texture gradients. Drawings in the top row show fairly “pure” examples of each of the pictorial depth cues. In the bottom row, the pictorial depth cues are used to assemble a more realistic scene. Table of Contents Exit

15. Fig. 6.15 On a dry lake bed, relative size is just about the only depth cue available for judging the camera’s distance from this vintage aircraft. What do you estimate the distance to be? Table of Contents Exit

16. Fig. 6.17 The apparent motion of objects viewed during travel depends on their distance from the observer. Apparent motion can also be influenced by an observer’s point of fixation. At middle distances, objects closer than the point of fixation appear to move backward; those beyond the point of fixation appear to move forward. Objects at great distances, such as the sun or moon, always appear to move forward. Table of Contents Exit

18. Fig. 6.7 An impossible figure—the “three-pronged widget.” Table of Contents Exit

19. Fig. 6.19 The Ponzo illusion may help you understand the moon illusion. Picture the two white bars as resting on the railroad tracks. In the drawing, the upper bar is the same length as the lower bar. However, because the upper bar appears to be farther away than the lower bar, we perceive it as longer. The same logic applies to the moon illusion. Table of Contents Exit

21. Fig. 6.9 Human infants and newborn animals refuse to go over the edge of the visual cliff Table of Contents Exit

22. Animation – Ames Room Table of Contents Exit

23. Fig. 6.24 The Ames room. From the front, the room looks normal; actually, the right-hand corner is very short, and the left-hand corner is very tall. In addition, the left side of the room slants away from viewers. The diagram shows the shape of the room and reveals why people appear to get bigger as they cross the room toward the nearer, shorter right corner. Table of Contents Exit

24. Fig. 6.27 Some interesting perceptual illusions. Illusions are a normal part of perception. Table of Contents Exit

25. Fig. 6.28 Why does line (b) in the Müller-Lyer illusion look longer than line (a) ? Probably because it looks more like a distant corner than a nearer one. Because the vertical lines form images of the same length, the more “distant” line must be perceived as larger. As you can see in the drawing on the right, additional depth cues accentuate the Müller-Lyer illusion. (After Enns & Coren, 1995.) Table of Contents Exit

29. Fig. 6.22 The effects of prior experience on perception. The doctored face looks far worse when viewed right side up because it can be related to past experience. Table of Contents Exit

35. Fig. 6.36 ESP cards used by J. B. Rhine, an early experimenter in parapsychology. Table of Contents Exit

36. Fig. 6.37 Fake psychokinesis. (a) The performer shows an observer several straight keys. While doing so, he bends one of the keys by placing its tip in the slot of another key. Normally, this is done out of sight, behind the “psychic’s” hand. It is clearly shown here so you can see how the deception occurs. (b) Next, the “psychic” places the two keys in the observer’s hand and closes it. By skillful manipulation, the observer has been kept from seeing the bent key. The performer then “concentrates” on the keys to “bend them with psychic energy.” (c) The bent key is revealed to the observer. “Miracle” accomplished! (Adapted from Randi, 1983.) Table of Contents Exit (a) (b c)