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Let’s Get Visual!.

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Presentation on theme: "Let’s Get Visual!."— Presentation transcript:

1 Let’s Get Visual!

2 Sensation & Perception
2/17/2019 What We See p. 125 Hue Visual experience specified by color names and related to the wavelength of light. Intensity Influences brightness and related to the amplitude of the light wave ©1999 Prentice Hall

3 Volunteer Time!! Use something of color and wiggle it on either side of student (pencil with eraser, etc.) Ask them to say when they see something and on what side of their head, ask them what color. They’ll detect something before they detect the color. Why do you think this is?? Cones are in the middle part of our eye and they detect color (cones, center, color). Rods are peripheral and detect movement (think moving a fish rod).

4 Sensation & Perception
2/17/2019 An Eye on the World Cornea Protects eye and bends light toward lens. Lens Focuses on objects by changing shape. Iris Controls amount of light that gets into eye. Pupil Widens or dilates to let in more light. ©1999 Prentice Hall

5 The Structures of the Retina
Sensation & Perception 2/17/2019 The Structures of the Retina Cones (Fewer) Rods (More) Near fovea Located in peripheral of the retina Responds to color Dark-adapted vision, scotopic More detail, higher resolution More sensitive to light, motion 127 Do you notice that your eyes hurt after the teacher has had the lights off for a video and they turn them back on? That is your rods reacting. ©1999 Prentice Hall

6 Do we see with our eyes or our brains?
Watch spiral for at least 30 second and then look picture… map? Ask – what is controlling the spiral? Our eyes or brains? Lets test it! Look at the spiral again but with one eye covered. Then look at the picture with the eye that was covered (covering the eye that wasn’t covered). Does is still spiral? YES! Your brain is controlling this, it’s perception. Was the spiral going the same direction? Or did it switch? It switched because we have different “feature detectors” in our brain that detect different things. The detector for one direction were fatigued so the detectors for the opposite direction fired. The Optical Spiral

7 Hubel & Wiesel’s Experiment
Sensation & Perception 2/17/2019 Hubel & Wiesel’s Experiment Much visual processing is done in the brain. Feature Detectors p. 129 Some cortical cells respond to lines in specific orientations Other cells in the cortex respond to other shapes Much visual processing is done in the brain. Some cortical cells respond to lines in specific orientations (e.g. horizontal). Other cells in the cortex respond to other shapes (e.g., bulls-eyes, spirals, faces). Feature-detectors Cells in the visual cortex that are sensitive to specific features of the environment. ©1999 Prentice Hall

8 Sensation & Perception
2/17/2019 How We See Colors Young Helmholtz Trichromatic theory Opponent process theory Figure 5.04 from Wade, C., & Tavris, C. (2002). Invitation to Psychology, 2nd Ed. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

9 Sensation & Perception
2/17/2019 Trichromatic Theory Young (1802) & von Helmholtz (1852) both proposed that the eye detects 3 primary colors: red, blue, & green All other colors can be derived by combining these three. Figure 3.9 from: Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall. All colors together create white. ©1999 Prentice Hall

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11 What do you see?! American flag Again your receptors for one color are fatigued so the receptors behind it fire.

12 Stare at the four dots…

13 What do you see? Jesus

14 Opponent-Process Theory
Sensation & Perception 2/17/2019 Opponent-Process Theory A competing theory of color vision, which assumes that the visual system treats pairs of colors as opposing or antagonistic. Opponent-Process cells are inhibited by a color, and have a burst of activity when it is removed. ©1999 Prentice Hall

15 What’s Happening? In the retina of your eyes, there are 3 types of color receptors (cones) that are most sensitive to either red, blue or green. When you stare at a particular color for too long, these receptors get "tired" or "fatigued." When you then look at the white background, the receptors that are tired do not work as well. Therefore, the information from all of the different color receptors is not in balance and you see the color "afterimages." You can see that you vision quickly returns to normal.

16 Test of Color Deficiency
Sensation & Perception 2/17/2019 Test of Color Deficiency Figure 3.12 from: Kassin, S. (1998). Psychology, second edition. Upper Saddle River, NJ: Prentice Hall. ©1999 Prentice Hall

17 Time Permitting Anatomy and function of the eye video


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