Visual Illusions

Illusions occur when:

• a person does not take into consideration all

  aspects of a sensation

• a sensation becomes physically distorted

• perception consistently differs from objective

  reality

• there is a failure in the biological processing

  of a stimulus.

The Müller-Lyer Illusion is one in which we

mistakenly think that one parallel line is longer

than the other because of the pattern on the end

of each of the lines. The best description of the

illusion is that:

• the line with the arrowheads on the ends is

  perceived to be shorter than the line with the

  feather-tails on the ends

• the line with the arrowheads on the ends is

  perceived to be longer than the line with the

  feather-tails on the ends

• the two lines are perceived to be the same

  length but at different distances from us

• the two lines are perceived to be the average

  length of the outermost and innermost

  measurements.

The Ponzo Illusion is a visual illusion of:

• curvature

• depth and distance

• size and shape

• motion.

The Ames Room provides an illusion because

of our familiarity with the rectangular shape of

rooms. It occurs because we:

• maintain size constancy at the expense of

  shape constancy

• maintain shape constancy at the expense of

  size constancy

• perceive that size and shape constancies

  are maintained

• perceive that neither size nor shape

  constancy is maintained.

‘Motion after-effect’ is an illusion of movement

caused by:

• reduced activity in motion-detecting

  neurons

• increased activity in motion-detecting

  neurons

• maintenance of motion constancy

• perceptual set caused by expectancy.

MAEs may occur:

• only in vision

• in vision and the tactile sense

• in vision, tactile senses and hearing

• in all senses.

These two faces of a cube:

• are the same shade

• are different shades of grey

• change depending on the angle from which you view them

• are actually blue and black

This illusion uses the gestalt principle of

• proximity

• similarity

• closure

• camouflage

This illusion confuses the brain's use of

• linear perspective

• shape constancy

• texture gradient

• size constancy

These parallel lines were first observed

• on tiles at the front of a cafe

• on the walls at the subway

• in an artwork by M.C. Escher

• In an ink blot psychology test