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).

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

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

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

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

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

VISION

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

Transduction occurs in the Retina Outline

Transduction Process by which our sensory systems encode stimulus as neural messages the brain can interpret Outline

Path light travels through the eye. Outline

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

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

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

Find your blind spot This is where the optic nerve has no receptor cells 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 Outline

Fovea: Retina’s area of central focus Cones and no rods 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. Outline

17 Feature Detection Individual 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

Trichromatic Color Theory We see color due to the R ED G REEN B LUE Cones in the retina Outline

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. Blue Green Red Medium Low Max Standard stimulus Comparison stimulus

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

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

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.

COLOR VISION

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

Neuroscience of ghosts! Outline

Alas poor Yorick it was an after- image! Outline

The Basic Process 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 Outline