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PSYCHOLOGY(8th Edition, in Modules)

David Myers

PSYCHOLOGY(8th Edition, in Modules)

David Myers

PowerPoint Slides

Worth Publishers, © 2007

PowerPoint Slides

Worth Publishers, © 2007

22

Vision

Module 13

Vision

Module 13

33

VisionVisionVision The Stimulus Input: Light

Energy

The Eye

Visual Information Processing

Color Vision

Vision The Stimulus Input: Light

Energy

The Eye

Visual Information Processing

Color Vision

44

TransductionTransduction

In sensation, transformation of stimulus energy into neural impulses.

Phototransduction: Conversion of light energy into neural impulses that brain

can understand.

In sensation, transformation of stimulus energy into neural impulses.

Phototransduction: Conversion of light energy into neural impulses that brain

can understand.

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VisibleSpectrum

The Stimulus Input: LightThe Stimulus Input: LightB

oth

Pho

tos:

Tho

mas

Eis

ner

66

The EyeThe Eye

77

Parts of the eyeParts of the eye

1. Cornea: Transparent tissue where light enters the eye.

2. Iris: Muscle that expands and contracts to change the size of opening (pupil) for light.

3. Lens: Focuses the light rays on the retina.

4. Retina: Contains sensory receptors that process visual information and send it to the brain.

1. Cornea: Transparent tissue where light enters the eye.

2. Iris: Muscle that expands and contracts to change the size of opening (pupil) for light.

3. Lens: Focuses the light rays on the retina.

4. Retina: Contains sensory receptors that process visual information and send it to the brain.

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The LensThe LensLens: Transparent structure behind

pupil that changes shape to focus

images on the retina.

Accommodation: The process by which the eye’s lens changes shape to help focus

near or far objects on the retina.

Lens: Transparent structure behind

pupil that changes shape to focus

images on the retina.

Accommodation: The process by which the eye’s lens changes shape to help focus

near or far objects on the retina.

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The LensThe LensNearsightedness: A condition in which nearby objects are seen more clearly

than distant objects.

Farsightedness: A condition in which faraway objects are seen more clearly than near objects.

Nearsightedness: A condition in which nearby objects are seen more clearly

than distant objects.

Farsightedness: A condition in which faraway objects are seen more clearly than near objects.

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RetinaRetinaRetina: The light-

sensitive inner surface of the

eye, containing receptor rods and cones plus layers of other neurons (bipolar, ganglion

cells) that process visual information.

Retina: The light-sensitive inner surface of the

eye, containing receptor rods and cones plus layers of other neurons (bipolar, ganglion

cells) that process visual information.

1111

Optic Nerve, Blind Spot & Fovea

Optic Nerve, Blind Spot & Fovea

http://www.bergen.org

Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where optic nerve leaves the eye, because there are no receptor cells located here, it creates a blind spot. Fovea: Central point in the retina, around which the eye’s cones cluster.

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PhotoreceptorsPhotoreceptors

E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969

1313

Visual Information Processing

Visual Information ProcessingOptic nerves connect to the thalamus in the middle of the brain, and

the thalamus to the visual cortex.

1414

Feature DetectionFeature DetectionNerve cells in the visual cortex respond to

specific features, like edges, angle, and movement.

Ros

s K

inna

ird/

Alls

port

/ Get

ty I

mag

es

1515

Shape DetectionShape DetectionSpecific combinations of temporal lobe activity occur as people look at shoes,

faces, chairs and houses.

Isha

i, U

nger

leid

er, M

artin

and

Hax

by/ N

IMH

1616

Perception in BrainPerception in BrainOur perceptions are a combination of

sensory (bottom-up) and cognitive (top-down) processes.

1717

Visual Information Processing

Visual Information Processing

Processing of several aspects of the stimulus simultaneously is called parallel processing. The

brain divides a visual scene into subdivisions such as color, depth, form and movement etc.

Processing of several aspects of the stimulus simultaneously is called parallel processing. The

brain divides a visual scene into subdivisions such as color, depth, form and movement etc.

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From Sensation to Recognition

From Sensation to Recognition

Tim

Bie

ber/

The

Im

age

Ban

k

1919

Theories of Color VisionTheories of Color VisionTrichromatic theory: Based on behavioral

experiments, Helmholtz suggested that retina should contain three receptors

sensitive to red, blue and green colors.

Trichromatic theory: Based on behavioral experiments, Helmholtz suggested that retina should contain three receptors

sensitive to red, blue and green colors.

Blue Green Red

Medium LowMax

Standard stimulus

Comparison stimulus

2020

Subtraction of ColorsSubtraction of Colors

If three primary colors (pigments)

are mixed it results in subtraction of all

wavelengths and the result is a black

color.

If three primary colors (pigments)

are mixed it results in subtraction of all

wavelengths and the result is a black

color.

2121

Addition of ColorsAddition of Colors

If three primary colors (lights) are mixed the wavelengths are added and they

result in white color.

If three primary colors (lights) are mixed the wavelengths are added and they

result in white color.

Fritz Goro, L

IFE m

agazine, © 1971 T

ime W

arner, Inc.

2222

PhotoreceptorsPhotoreceptorsRed

ConesGreenCones

Longwave

Mediumwave

Shortwave

MacNichol, Wald and Brown (1967)

measured directly the absorption

spectra of visual pigments of single cones

obtained from the retinas of humans.

BlueCones

2323

Color BlindnessColor Blindness

Ishihara Test

Genetic disorder in which people are blind to green or red colors supports Trichromatic

theory.

Genetic disorder in which people are blind to green or red colors supports Trichromatic

theory.

2424

Opponent ColorsOpponent Colors

Gaze at the middle of the flag for about 30seconds, when it disappears, stare at the dot and report

if you see Britain's flag.

2525

Opponent Process TheoryOpponent Process Theory

Hering, proposed that we process four primary colors opposed in pairs of red-green, blue-yellow, and black-white.

Hering, proposed that we process four primary colors opposed in pairs of red-green, blue-yellow, and black-white.

Cones

RetinalGanglion

Cells