1. Perception

2. Overview Perceptual Problems Solved by the Brain Perceptual Strategies Used by the Brain What do Illusions Tell Us?

3. Perceptual Problems Solved by the Brain The environment is three dimensional but the stimulation on the retinas is only two dimensional Perceptual constancy: we can perceive the same object even when the information reaching us varies  Size constancy  Color constancy What about those blind spots?

4. The Moon Illusion Problems for depth perception:  The retinal image is two dimensional  Size of the retinal image depends on both distance of the object and size of the object

5. Perceptual Strategies Used by the Brain Context: use surrounding information Example: Muller-Lyer Illusion

6. Perceptual Strategies Used by the Brain Top-Down Processing: use knowledge and experience Example: subjective contours

7. Gestalt Strategies The brain makes assumptions about the world that aid perception These assumptions are based on the Law of Pragnanz: perceive the simplest possible pattern Examples:  Proximity  Similarity  Closure

9. What Do Illusions Tell Us? Perception is not always accurate (but it usually is) Things that trick the brain can reveal how the brain works