Starter

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

2. 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

3. 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.

4. 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 because they make a large image on the retina. • This is how we maintain the relative size of objects regardless of their distance from us.

5. 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. • Distortionillusions often include angled lines.

6. 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.

7. 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.

8. 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.

9. 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)

10. The Muller-Lyer Illusion • 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. • Investigate the Muller-Lyer illusion, answering the following questions in your books, in FULL sentences: • Which depth cues does the Muller-Lyer illusion play on? • Explain how these depth cues should work ‘normally’ and explain how they affect the illusion.

11. 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.

12. 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

13. 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.