Visual Illusions

What is an optical illusion?

• A really cool drawing.

• A picture of something you can't explain.

• Something that tricks your mind and your eyes into believing something is happening when it really is not.

• It is something similar to a landscape.

A stimulus is considered an ‘illusion’ because...

• Even though we all experience it, scientists cannot explain why this stimulus works the way it does

• Our experience of this stimulus is affected by our cultural background and early experience

• There is a mismatch between physical reality and our own interpretation of it

• We experience the stimulus differently every time we view it

Which of the following visual depth cues cannot be used by the person viewing the Ames Room?

• Accommodation

• Retinal Disparity

• Relative Size

• Texture Gradient

People viewing the Ames room tend to maintain ( ) constancy but cannot maintain ( ) constancy

• Shape, Size

• Brightness, Colour

• Size, Shape

• Position, Brightness

Psychologist are interested in studying illusions such as the Ames room mainly

• it's an architectual wonder

• To learn more about brain organisation and functioning

• because such phenomena are fascinating

• in order to help people from being fooled by them

Which of the following is NOT an explanation proposed for why the Muller-Lyer illusion occurs?

• More eye movements are used to view the line with the inward pointing arrows compared to the line with outward pointing arrows and hence this line is perceived as being longer.

• The feather tail line resembles an inner corner of a room and the arrowhead line resembles the outer corner of a building. As the inner corner of a room is further away from the viewer, the feather tail line is perceived as longer.

• Cross- cultural studies show that those raised in rural areas with minimal or no experience with angles, edges and corners of buildings are much less likely to perceive the illusion.

• The illusion only works when the lines are vertical and viewers misapply size constancy in perceiving the inward pointing arrowhead line as longer.

The Ames Room demonstrates that

• viewing objects at a distance can distort perception

• perception is more accurate when we use monocular cues

• we can always maintain size constancy over shape constancy

• if two things appear to be the same distance away but have retinal images indicating difference in size, then perceived size is determined by the size of the retinal images

Figures tend to be perceived as whole, complete objects, even if spaces or gaps exist in the representation, thus demonstrating the principle of:

• Closure
• Proximity
• Continuity
• Similarity

The Muller Lyer Illusion demonstrates that if the retinal images of two lines are identical, then people who grew up in 'non-carpentered worlds'.....

• cannot be fooled

• purposefully ignore 'carpentered world' cues

• will usually perceive the lines as the same

• can make perceptual errors unless a ruler is available

• Young lady
• Older women