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Module 1.6b

your finger moves. Why do you see light? Why at the left? This happens because your retinal
cells are so responsive that even pressure triggers them. But your brain interprets their firing
as light. Moreover, it interprets the light as coming from the left — the normal direction of ENGAGE 1.6-6
light that activates the right side of the retina.
(5 minutes) Use Teacher Demonstra-
Color Processing tion: Subjective Colors to demonstrate
1.6-6 How do we perceive color in the world around us? the text’s discussion of color vision
How do we per
ceive color in the world ar
ound us?
1.6-6
to your students. This demonstration
We talk as though objects possess color: “A tomato is red.” Recall the old question, “If a tree illustrates subjective colors (colors that
falls in the forest and no one hears it, does it make a sound?” We can ask the same of color:
If no one sees the tomato, is it red? appear in the absence of the appropri-
The answer is No. First, the tomato is everything but red, because it rejects (reflects) the Young–Helmholtz ate wavelengths of light).
long wavelengths of red. Second, the tomato’s color is our mental construction. As Sir Isaac trichromatic (three-color)

Newton (1704) noted, “The [light] rays are not colored.” Like all aspects of vision, our percep- theory the theory that the retina M1.6b: Subjective Colors
contains three different types
tion of color resides not in the object itself but in the theater of our brain; even while dreaming, of color receptors — one most
we usually perceive things in color. Likewise, air molecules striking the eardrum are silent and sensitive to red, one to green,
scent molecules have no smell. Our brain creates experiences of sight, sound, and smell. one to blue — which, when
One of vision’s most basic and intriguing mysteries is how we see the world in color. stimulated in combination, can
How, from the light energy striking the retina, does our brain construct our experience of produce the perception of any PRACTICE
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
such a multitude of colors? color.
Modern detective work on the mystery of color vision began in the nineteenth century,
when German scientist Hermann von Helmholtz built on the insights of an English physicist, Research Methods & Design
Thomas Young. Both knew that any color can be created by combining the light waves of
three primary colors — red, green, and blue. So Young and von Helmholtz’s research led to a (SP 2)
hypothesis: The eye must have three corresponding types of color receptors. (10 minutes) Take this time to
®
Researchers later confirmed the Young–Helmholtz trichromatic (three-color) AP Science Practice review hypotheses with students.
theory by measuring the responses of various cones to different color stimuli. The retina does Research
indeed have three types of color receptors, each especially sensitive to the wavelengths of Recall from Unit 0 that a hypoth- Remind them that the researchers’
red, green, and blue. When light stimulates combinations of these cones, we see other colors. esis is a falsifiable prediction that hypothesis should determine their
For example, the retina has no separate receptors especially sensitive to yellow. But when red can be used to check the theory or research methods. In small groups,
and green wavelengths stimulate both red-sensitive and green-sensitive cones, we see yellow. produce practical applications of it.
By testing Young and Helmholtz’s
Said differently, when your eyes see red and green without blue, your brain says yellow. hypothesis, researchers supported have them come up with a few
Worldwide, about 1 in 12 males and 1 in 200 females have the genetically sex- their theory of color vision. hypotheses about color vision on
linked condition of color-deficient vision. Most with color vision deficiency are not entirely their own.
“colorblind”: They simply lack functioning red- or green-sensitive cones, or sometimes both.
Their vision — perhaps unknown to them, because their lifelong vision seems normal — is

monochromatic (one-color) or dichromatic (two-color) instead of trichromatic, making
it impossible to distinguish the red and green in Figure 1.6-13 ( Boynton, 1979 ). Dogs, too,

lack receptors for the wavelengths of red, giving them only limited, dichromatic color vision Figure 1.6-13
( Neitz et al., 1989 ). Copyright © Bedford, Freeman & Worth Publishers.
Color-deficient vision
The photo in image (a) shows ENGAGE 1.6-6
how people with red-green
deficiency perceived a 2015 (Out of class) People who have
Ben Solomon/The New York Times/Redux Pictures of Americans like me that are red- they are deficient in as a shade of
Buffalo Bills versus New York Jets
color-deficient vision see the color
football game. “For the 8 percent
green colorblind, this game is a
nightmare to watch,” tweeted one
muted gray or brown. They’ve been
fan. “Everyone looks like they’re
trained, however, to identify that
on the same team,” said another.
The photo in image (b) shows
viewers with normal color vision.
(depending on their deficiency). As a
(a) (b) how the game looked for those muted “color” as red, blue, or green
result, unless they have been tested,
Sensation: Vision Module 1.6b 129 they usually do not know they have
color-deficient vision. Use Student
Activity: The Color Vision Screening
Inventory to assess color-deficient
ENGAGE 1.6-6
03_myersAPpsychology4e_28116_ch01_002_163.indd 129 15/12/23 9:25 AM
vision in students.
(10 minutes) Have students experience
colorblindness by visiting the Colour Blind M1.6b: The Color Vision
Awareness website at colourblindawareness. Screening Inventory
org/colour-blindness/colour-blindness-
experience-it. Have them discuss what they
learned as you introduce color processing.
Sensation: Vision Module 1.6b 129

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