- Title Pages
- How to Use the Website
- Chapter 11 Weighted Positional Averaging in the Illusions of the Müller-Lyer Type
- Chapter 12 The Bar-Cross-Ellipse Illusion
- Chapter 13 The Spinning Ellipse Speed Illusion
- Chapter 14 The Ames Window Illusion and Its Variations
- Chapter 15 Three-Dimensional Müller-Lyer Illusion
- Chapter 16 Why Do Hills Look So Steep?
- Chapter 17 “Shape From Smear”
- Chapter 18 Geometric-Optical Illusions Under Isoluminance?
- Chapter 19 The Picture Surface Illusion
- Chapter 20 Cast Shadow Illusions
- Chapter 21 The Leaning Tower Illusion
- Chapter 22 The Invisible Saddle, or the Cap-or-Cup Illusion
- Chapter 23 Symmetry and Uprightness in Visually Perceived Forms
- Chapter 24 The Bathtub Illusion
- Chapter 25 The Pitchroom Illusion
- Chapter 26 Geometric Illusions in the Human Face and Body
- Chapter 27 Dynamic Illusory Size Contrast
- Chapter 28 Size Contrast and Assimilation in the Delboeuf and Ebbinghaus Illusions
- Chapter 29 The Occlusion, Configural Shape, and Shrinkage Illusions
- Chapter 30 Reverse-Perspective Art and Objects—Illusions in Depth and Motion
- Chapter 31 The <i>New</i> Moon Illusion
- Chapter 32 Geometrical Errors Are the Cost of Maintaining the Luminance Contrast Polarity
- Chapter 33 Antigravity Slopes
- Chapter 34 The Geometric-Optical Illusions of J. J. Oppel
- Chapter 35 The Oppel–Kundt Illusion
- Chapter 36 The Shifted-Chessboard Pattern as Paradigm of the Exegesis of Geometrical-Optical Illusions
A New Type of Visual Illusion
- (p.295) Chapter 33 Antigravity Slopes
- The Oxford Compendium of Visual Illusions
- Oxford University Press
A new type of illusion, called the antigravity slope illusion, is presented in this chapter. In this illusion a slope orientation is perceived opposite to the true orientation and hence a ball put on it appears to be rolling uphill, defying the law of gravity. This illusion is based on the ambiguity in the distance from a viewpoint to the surface of a three-dimensional solid represented in a single-view image. This illusion also arises in human real life, for example, when a car driver misunderstands the orientation of a road along which he or she is driving. Two assumptions are explored: (a) the human brain prefers to interpret vertical columns in a two-dimensional image as being vertical in three-dimensional space to being slanted and (b) the human brain prefers the most symmetric shape as the interpretation of a two-dimensional image.
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