Some of these are binocular cues, which means that they rely on the use of both eyes. We use a variety of cues in a visual scene to establish our sense of depth. Our world is three-dimensional, so it makes sense that our mental representation of the world has three-dimensional properties. With depth perception, we can describe things as being in front, behind, above, below, or to the side of other things. Our ability to perceive spatial relationships in three-dimensional (3-D) space is known as depth perception. You can test this concept using the flag in Figure 2. When color is involved in the stimulus, the color pairings identified in the opponent-process theory lead to a negative afterimage. For example, when you stare briefly at the sun and then look away from it, you may still perceive a spot of light although the stimulus (the sun) has been removed. An afterimage describes the continuation of a visual sensation after removal of the stimulus. Another implication is that this leads to the experience of negative afterimages. One of the implications of opponent processing is that we do not experience greenish-reds or yellowish-blues as colors. So, a cell that was excited by wavelengths associated with green would be inhibited by wavelengths associated with red, and vice versa. The basic idea is that some cells of the visual system are excited by one of the opponent colors and inhibited by the other. According to this theory, color is coded in opponent pairs: black-white, yellow-blue, and green-red. The trichromatic theory of color vision is not the only theory-another major theory of color vision is known as the opponent-process theory. Comparatively, only about 0.4% in females from European Caucasian descent have red-green color deficiency (Birch, 2012). Approximately 8% of males with European Caucasian decent, 5% of Asian males, 4% of African males, and less than 2% of indigenous American males, Australian males, and Polynesian males have red-green color deficiency (Birch, 2012). The most common X-linked inherited abnormality is red-green color blindness (Birch, 2012). Seeing in grayscale (only shades of black and white) is extremely rare, and people who do so only have rods, which means they have very low visual acuity and cannot see very well. The Ishihara test evaluates color perception by assessing whether individuals can discern numbers that appear in a circle of dots of varying colors and sizes. Fortunately, other than unknowingly being badly dressed, my colorblindness rarely harms my day-to-day life.įigure 2. I cannot differentiate between most greens, browns, and reds. It was then that I found out that I was colorblind. After several days of being told that my coworkers just thought I had “a really unique style,” I made an appointment with an eye doctor and was tested (Figure 5.15). She looked at my quizzically and said, “No way do your clothes match.” Over the next few days, I started asking my coworkers and friends if my clothes matched. She said my pants were a bright green color, my shirt was a reddish orange, and my tie was brown. As a single father with no one else to ask at home, I drove us to the nearest convenience store and asked the store clerk if my clothes matched. She had complained frequently that I was bad at matching my shirts, pants, and ties, but this time, she sounded especially alarmed. She looked up at me, and in her most stern voice, said, “You can’t wear that.” I asked, “Why not?” and she informed me the colors of my clothes did not match. Several years ago, I dressed to go to a public function and walked into the kitchen where my 7-year-old daughter sat. Connect the concepts Colorblindness: A Personal Story
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