1. Critical Thinking: Science and Pseudoscience
David E. Thomas
PSY 131
July 27th, 2015
Week 8, Lecture 28
Optical Illusions

2. Agenda
Optical Illusions
How do they Work?

3. Which is Longer? And, Why?

4. Perspective and Size

5. Perspective and Size

6. Perspective
Shephard's illusion

7. Escher-Style Illusions: 3D Ambiguity, Necker Cubes

8. 3D Ambiguity

9. 3D Ambiguity

10. 3D Ambiguity
How can you remove one of the glasses from the tray?

11. 3D Ambiguity

12. 3D Ambiguity

13. 3D Ambiguity

14. Shadows and Brightness
Top Gray = Bottom White

15. Shadows and Brightness

16. Shadows and Brightness

17. Shadows and Brightness
Different people see this differently!

18. Color Exhaustion

19. Color Exhaustion

20. Color Exhaustion – John Sadowski

21. Paired Color Cells - Explanation
Some ganglions (nerve cells) process red and green colors (opposites), but only one a a time. Others process blue and yellow colors (again, opposites), and again, one at a time.
When you stared at the false-color image, the cells seeing orange (sky) got tired, likewise for the cells seeing blue (castle), causing a bright blue sky and tawny castle.

22. Color Exhaustion

23. Perception of Embedded Colors
Green on left, Blue on Right?

24. Perception of Embedded Colors

25. Perception of Embedded Colors

26. Perception of Embedded Colors
The orange stripes go through the "green" spiral but not the "blue" one?

27. Perception of Embedded Colors
Violet on left, Pink on Right?

28. Hodgepodge Optical Illusions

29. Visual Continuity

30. Seeing things that Do Not Exist
Lateral Inhibition – Response of some cells reduced when neighbors are also firing...

31. More Lateral Inhibition

32. More Lateral Inhibition

33. Presentation by Implication

34. How many Circles?

35. This is not an Animated GIF!

36. This is not an Animated GIF!

37. Coarse versus Fine Detail

38. Perception of Motion

39. Change Blindness
With Interruptions

40. Change Blindness
Without Interruptions

41. Distance-Dependent Illusion

42. Motion
Clockwise, or Counterclockwise?

43. Motion and Continuity

44. This IS an Animated GIF!

45. This IS an Animated GIF!

46. Motion Exhaustion...

47. Peripheral Motion Illusion...
/best-new-visual-illusions-curveball

48. Peripheral Vision and Time

49. Peripheral Vision and Time
Blank:
Both:
Illusion:
Not so much:

50. Student Soapbox