Starter

On the sheet, next to the image write what type of Monocular depth cues are shown.

Learning Objectives

• To understand and evaluate Gregory’s theory of illusions.

• To understand the experimental method.

Success Criteria

• To present an evaluation of Gregory’s theory.

• To write a definition of the Muller-Lyer experiment

Gregory’s Theory of Illusions

• To understand this theory you need to make sure you clearly understand – Size Constancy.

– Monocular Depth Cues.

– Binocular Depth Cues.

Depth Cues

• REMEMBER: When we judge an object to be far away, we scale it up because distant objects make small images on the retina. • Nearby objects are scaled down

large

because they make a image on the retina. • This is how we maintain the relative size from us.

of objects regardless of their distance

Gregory’s Theory of Illusions

• Look back to Linear perspective: What is it?

• Linear Perspective is a depth cue. • It is the apparent meeting of a set of parallel lines in the distance. • Distortion illusions often include angled lines.

Gregory’s Theory of Illusions

• Look at the radiating lines of the Hering illusion to the right.

• According to Gregory, we interpret the patterns in illusions as if they were depth cues. We then apply size constancy scaling and distort our perception.

• Copy down the above point into your book, Title:

Gregory’s theory.

Hering Illusion

• Stick the image of the Hering Illusion in your book, in the centre of the top of your page, giving it a title.

The Hering Illusion

• If the radiating lines act as linear perspective cues then we would use constancy scaling as if the scene really had depth.

• The person who appear ‘furthest away; would be scaled up so they look bigger. • The person who appears closest would be scaled down, and look smaller. • This is exactly what we see.

• Now label this on your picture.

Gregory’s Theory of Illusions

• Basically: the interpretation of depth cues can cause us to experience illusions, for example the Ponzo illusion (left) and Hering illusion. (draw images)

The Muller-Lyer Illusion

• Investigate the Muller-Lyer • Write a brief explanation of the Muller-lyer illusion • Basically: (draw image) linear perspective and constancy scaling cause us to perceive the left line as shorter than the right line.

Evaluating Gregory’s theory

• Prepare an argument evaluating Gregory’s theory.

• You must include both sides of the argument ( for and against ) and include a conclusion.

Learning Objectives

• To understand and evaluate Gregory’s theory of illusions.

• To understand the experimental method.

Success Criteria

• To present an evaluation of Gregory’s theory.

• To write a definition of the Muller-Lyer experiment

Plenary

• Is this inside or outside the book, explain how Gregory’s theory would explain this distortion illusion.

It could be either, Gregory would say that the angled lines are interpreted as a three dimensional figure. The Angled lines could point forwards or backwards.