1. PSYCH JOURNAL 9/24/2013 Vision is the most frequently studied sense. Why do you think this is the case? Why is vision so important? How would your life be different if you could no longer see?

2. Vision How do we see the world?

3. Vision is the most frequently studied of all senses. Why? We are most active during the day, therefore rely on this sense (nocturnal animals rely more on hearing) Loss of vision is devastating Arguably vital for survival More information about the outside world comes in through our eyes than any other sense organ

4. How do we see? Light travels in waves Characteristics of waves impact our vision Step 1: Gathering light

5. Hue Refers to color Is determined by the length of the wave Long waves are red/orange Short waves are blue/purple

6. Brightness Refers to intensity of light Is determined by the height of a wave High waves are bright Low waves are dim

7. Saturation Refers to the purity of the color Highly saturated have few different wavelengths Less saturation has more wavelengths ▫Example:  Highly saturated red, have only red wavelengths  Less-saturated red would have a mixture of wavelengths White light lacks any color and is completely unsaturated Highly Saturated Highly Unsaturated

8. http://www.youtube.com/watch?v=ShUeUVOy K84

9. How do we see? Retina – neural tissue lining the back of the eyeball’s interior, which contains the receptors for vision (rods and cones) Step 2: Light enters eye, is processed into neural impulses

10. Rods and Cones Receive light and process it into neural signals Rods – Visual receptors that respond to dim light Cones – Visual receptors involved in color vision

11. Dark Adaptation Visual receptors become sensitive to dim light. Chemical changes in rods and cons. Cones – 10 minutes Rods – 20 minutes

12. How do we see? Rods and cones communicate with neurons which send visual information to the optic nerve The optic nerve then carries info out the back of the eye to the brain The thalamus sends the visual information to the occipital lobe in the cerebral cortex (processed on opposite side) Step 3: On to the brain

13. Theories of Color Vision Applies to stage of color processing that occurs in the eye States that the retina contains three basic types of cones: red, blue, and green cones The colors we see result from combined activity of these three types of cones Trichromatic Theory

14. Color Blindness Occurs because of defective cones in the retina of the eye Most common: red-green color blindness ▫Either red or green cones do not work

15. Applies to the stage of color processing that occurs in both the retina and in neurons in the brain The theory states that cones are arranged in pairs with a red-green pair and a blue-yellow pair. If one member of the pair is firing, then the other member cannot Afterimage-Occurs when a visual sensation persists for a brief time even after the original image is removed Theories of Color Vision Opponent-Process Theory