Muller Lyer Illusion

Question 1

The illusion

Answer 1

• The Müller-Lyer illusion is an optical illusion consisting of a set of lines that end in arrowheads. The orientation of the arrowheads affects one’s ability to accurately perceive the length of the lines.

Question 2

Uses of the illusion

Answer 2

• Like most visual and perceptual illusions, the Müller-Lyer illusion helps neuroscientists study the way the brain and visual system perceive and interpret images. Artists have also utilized the illusion to great effect in their works.

Question 3

Perspective explanation

Answer 3

• In the three-dimensional world, we often use angles to judge depth and distance. Living in a “carpentered world,” we have grown accustomed to seeing corners everywhere. The brain is used to viewing such angles and interpreting them as far and near corners, and also uses this information to make size judgments. When looking at the Müller-Lyer arrows, the brain interprets them as far and near corners, and overrides the retinal information that says both lines are the same length.

Question 4

eye movement theory

Answer 4

we perceive one line as longer because it takes more eye movements to view a line with inward pointing arrows than it does a line with outward pointing arrows. This explanation is largely dismissed, as the illusion persists even when there is no eye movement at all.

Question 5

Assimilation theory

Answer 5

we see one line as longer because the visual system is unable to separate the figure into parts. As a whole figure, the line with inward pointing arrows is indeed longer. This theory is also generally dismissed.

Question 6

Richard Gregory

Answer 6

this illusion occurs because of a misapplication of size constancy account. In the three dimensional world, this principle allows us to perceive a tall person as tall whether they are standing next to us or off in the distance. When we apply this same principle to two-dimensional objects, Gregory suggests, errors can result.