12 Visual Illusions

Question 1

Q: What is the origin and meaning of the word “illusion”?

Answer 1

A: The word “illusion” comes from the Latin word “illudere,” which means to mock.

Question 2

Q: What causes an illusion according to the brain’s perceptual process?

Answer 2

A: Illusions occur when the brain’s perceptual hypothesis about the data being presented is incorrect, leading to a misinterpretation of what is physically present in the world.

Question 3

Q: What does the occurrence of illusions suggest about our perception?

Answer 3

A: The occurrence of illusions suggests that the eye is not a passive camera and that perception is an active process that happens in the brain.

Question 4

Q: What are illusions classified as according to Gregory (1983)?

Answer 4

A: According to Gregory (1983), illusions are classified into four categories: distortions, ambiguous figures, paradoxical figures, and fictions.

Question 5

Q: How many different theories are there about distortions?
What are the examples?

Answer 5

A: There are 12 different theories about distortions.
Muller-lyer, ponzo, poggendorf, herring, wundt, titchner.

Question 6

Q: What is the Müller-Lyer illusion and how does Gregory (1966) explain it?

Answer 6

A: The Müller-Lyer illusion involves two lines with different fins at the ends, making one appear longer than the other. Gregory (1966) explains it based on misapplied size constancy, where fins on the blue line make it look like an inside corner of a room (appearing farther away) and fins on the red line make it look like an outside corner (appearing closer).

Question 7

Q: Is the Müller-Lyer illusion cross-cultural?

Answer 7

A: No, people who live in natural environments are less prone to the Müller-Lyer illusion.

Question 8

Q: What is the Ponzo illusion?

Answer 8

A: The Ponzo illusion involves two lines converging towards a vanishing point, making the line nearer the vanishing point appear larger due to perceived depth.

Question 9

Q: How does the orientation of the converging lines affect the Ponzo illusion?

Answer 9

A: When the converging lines are at the bottom, the sense of perspective diminishes, and the two lines appear the same length.

Question 10

Q: What is the Poggendorff illusion and how is it explained?

Answer 10

A: The Poggendorff illusion involves a straight line that appears misaligned when it passes behind a rectangle. It is explained by actual angle dilation, where small angles are perceived as larger than they are.

Question 11

Q: What is the Hering illusion?

Answer 11

A: The Hering illusion makes straight lines appear to bow out in the center due to the interpretation of radiating lines as depth cues, with central spots perceived as farther away than the edges.

Question 12

Q: What is the Wundt illusion?

Answer 12

A: The Wundt illusion has an effect opposite to the Hering illusion, making straight lines appear to bow inward.

Question 13

Q: What is the Titchner illusion and how does the brain process it?

Answer 13

A: The Titchner illusion involves circles of different sizes, where the brain overemphasizes size differences in grouping and separating objects.

Question 14

Q: What do distortion illusions reveal about the brain’s processing?

Answer 14

A: Distortion illusions reveal the complex depth and size calculations that the brain continuously performs and highlight the challenges posed by interpreting 2D drawings as 3D representations.

Question 15

Q: What is the Necker cube illusion?

Answer 15

A: The Necker cube is an ambiguous figure where a 2D drawing of a cube appears to flip between two orientations, making it unclear which face is at the front.

Question 16

Q: How does the brain interpret the Necker cube?

Answer 16

A: The brain automatically visualizes it as a 3D cube, but the drawing doesn’t provide enough information for the visual system to determine which face is at the front, leading to a flip between two interpretations.

Question 17

Q: What are paradoxical figures, and give an example.

Answer 17

A: Paradoxical figures are images that the brain tries to interpret as 3D but are impossible shapes, like the Penrose triangle, which appears as a single continuous surface but cannot exist in three-dimensional space.

Question 18

Q: Why does the Penrose triangle appear paradoxical?

Answer 18

A: The brain makes a false assumption that the triangle is in one plane, but parts of the triangle extend in impossible ways, showing how our brain tries to perceive depth even in flat images.

Question 19

Q: What is the Kanizsa triangle illusion?

Answer 19

A: The Kanizsa triangle creates the illusion of a bright white triangle overlaying three black circles with missing sectors, even though no actual triangle is present.

Question 20

Q: What is the Ames room illusion?

Answer 20

A: The Ames room illusion is an effect where a room appears cubic when viewed from a specific point, but is actually trapezoidal, causing objects or people to appear to grow or shrink as they move within it.

Question 21

Q: How does the Ames room create the illusion of different sizes?

Answer 21

A: By preventing the use of binocular depth cues with a single peephole, and because the brain assumes it is looking at a normal rectangular room, differing visual angles make objects or people appear to change size.

Question 22

Q: What are fictions in the context of visual illusions?

Answer 22

A: Fictions are unreal shapes perceived by the brain, like the Kanizsa triangle, ames room, where subjective contours and visual assumptions create the illusion of shapes that don’t exist in the image.

Question 23

Q: How do illusions like the Kanizsa triangle illustrate our perception of brightness and depth?

Answer 23

A: Our brain assumes near objects block distant ones and that nearer objects are brighter, leading to the perception of the illusory triangle as closer and brighter than the surrounding shapes.

Question 24

What are 2 unresolved/ new illusions?

Answer 24

moon, ouchi.

Question 25

Q: What is the Moon illusion?

Answer 25

A: The Moon illusion is a phenomenon where the Moon appears much larger when it is on the horizon compared to when it is directly overhead.

Question 26

Q: What is the apparent distance theory related to the Moon illusion?

Answer 26

A: The apparent distance theory, proposed by Kaufman and Rock in 1962, suggests that we perceive the sky as a flattened dome, making the Moon on the horizon appear farther away and thus larger than when it is overhead.

Question 27

Q: Why does the Moon illusion cause significant disagreement among researchers?

Answer 27

A: Helen Ross (2002) noted that the Moon illusion might cause the most bitter disagreement because the exact reasons behind the illusion are still not fully understood and various theories exist.

Question 28

Q: What is the Ouchi illusion?

Answer 28

A: The Ouchi illusion involves a pattern that causes a perception of movement due to the way our eyes and brain compensate for small involuntary eye movements.

Question 29

Q: How do eye movements contribute to the Ouchi illusion?

Answer 29

A: Even when fixated, our eyes make small random movements. These are usually compensated for at the fovea but not in the periphery, causing the perception of movement in the Ouchi pattern.

Question 30

Q: Why are visual illusions important in understanding perception?

Answer 30

A: Visual illusions help us become consciously aware of the intricate processes that our brain conducts unconsciously to create the visual world we perceive, demonstrating the active nature of our mind in searching for patterns and interpretations.

Question 31

Q: What do visual illusions reveal about our perceptual systems?

Answer 31

A: Visual illusions reveal that our perceptual systems are not inadequate but are instead highly active and complex, continuously creating interpretations from sensory data.