Unit 4: Sensation, Perception

1. JHS AP Psychology Unit 4: Sensation, Perception Essential Task 4-2:Describe the sensory process of vision including the specific nature of energy transduction (rods and cones and the trichromatic theory of color vision), relevant anatomical structures (cornea, pupil, iris, lens, retina, optic nerve, blind spot and fovea) and specialized pathways in the brain (opponent process theory of color vision and the occipital lobe).

2. Perceptual Constancies Gestalt Principles Basic Principles Visual Illusions Depth Perception Perception We are here Vision Hearing Sensation Theories The Eye Theories Other Senses The Ear Smell Pain Taste

3. Essential Task 4-2: Outline • Vision - relevant anatomical structures • Path light travels (cornea, pupil, iris, lens, and retina) • optic nerve, blind spot and fovea • Transduction (rods and cones) • Color Vision • The trichromatic theory of color vision • Color Blindness • Opponent process theory of color vision • After-Image Effect

4. TRANSDUCTION • The process by which our sensory systems encode stimulus energy as neural messages the brain can interpret • Conversion of one form of energy to another VISION – we convert light energy into neural impulses

5. VISION We don’t see color, but electromagnetic energy – we interpret color

6. VISION • Wavelenghth (distance from one peak to the next) = DETERMINES HUE (color) • INTENSITY (amount of energy in wave shown by height or amplitude) = DETERMINES BRIGHTNESS

7. VISION

8. EYE • Light enters through CORNEA • IRIS controls pupil size (light enters) • LENS changes shape to focus rays on RETINA • RETINA’s receptor cells convert the light into neural impulses • Impulses travel along OPTIC NERVE to brain…upside down image/rightens

9. Transduction occurs in the Retina Outline

10. TransductionProcess by which our sensory systems encode stimulus as neural messages the brain can interpret Outline

11. Path light travels through the eye. Outline Outline

12. ACUITY – sharpness of vision Distortions in shape of eye affects actuity NEARSIGHTEDNESS: misshapen eyeball focus light rays in front of retina (instead

13. RETINA: Rods and Cones Outline • Light energy goes through outer layer of cells to the RECEPTOR CELLS or the RODS AND CONES • These create neural signals • These activate GANGLIAN cells • These become the optic nerve and carry information to brain

14. RODS AND CONES • RODS = BLACK AND WHITE VISION • CONES = COLOR If illuminated, cones ineffectual, but rods remain sensitive in dim light Darkened room – pupils dilate to allow more light into rods: 20 minutes

15. Find your blind spotThis is where the optic nerve has no receptor cells Outline Take your right hand touch your index finger to your nose and then extend the arm all the way out keeping your finger extended. Stare at a point on the far wall beyond that finger Move the finger to the right by about 6 inches (up and down slightly) until you see the tip of the finger disappear into the blind spot

16. Fovea: Retina’s area of central focusCones and no rods Outline Central fovea (Fovea Centralis) is responsible for visual acuity and color sensitivty. The green and red cones are concentrated in the fovea centralis. The ‘Blue’ cones  are mostly found outside the fovea centralis.

17. Feature DetectionIndividual gaglion cells register infor in their region – send to visual cortex Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. Ross Kinnaird/ Allsport/ Getty Images

18. Shape Detection Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and houses. Ishai, Ungerleider, Martin and Haxby/ NIMH

19. Visual Information Processing Processing of several aspects of the stimulus simultaneously is called parallel processing. DOING SEVERAL THINGS AT ONCE!!! The brain divides a visual scene into subdivisions such as color, depth, form, movement, etc.

20. From Sensation to Recognition

21. Trichromatic Color Theory Outline • We see color due to the RED GREEN BLUE Cones in the retina

22. Color Vision Trichromatic theory: Young and von Helmholtz suggested that the eye must contain three receptors that are sensitive to red, blue and green colors. Standard stimulus Comparison stimulus Max Low Medium Blue Red Green

23. Color Blindness Genetic disorder in which people are blind to green or red colors. This supports the Trichromatic theory. Ishihara Test

24. Color Blindness Outline Dichromatic problems with reds and greens Dichromatic Problems with reds and greens Dichromatic Problems with Blues and Greens

25. Color Blindness Tests Outline

26. Opponent Colors Gaze at the middle of the flag for about 30 Seconds. When it disappears, stare at the dot and report whether or not you see Britain's flag.

27. COLOR VISION

28. Opponent Process theory helps us explain the after-image effect Outline

30. Neuroscience of ghosts! Outline

31. Alas poor Yorick it was an after-image! Outline

32. The Basic Process Outline • Receptor cells • Specialized cells that respond to a particular type of energy • Transduction-external energy is converted to neural signals. • Doctrine of specific nerve energies • One-to-one relationship between stimulation of a specific nerve and the resulting sensory experience • For example, applying pressure with your finger to your eye results in a visual experience