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Chapter 4b - Color and Perception Video Lecture Psych 1XX3

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Joe Kim

Video LecturePsych 1XX3Chapter 4 Sensory Systems Color and Perception The ability to see color is not due to the objects being inherently colorfulObjects reflect certain wavelengths of the visible spectrumthese reflected wavelengths trigger specific patterns of response in the brain that give rise to our subjective experience of colorEvolution of Color Perception Why and WhoAmong mammals color vision is limited to primatesPrimary color vision is especially well suited to distinguish red and yellow against a green backgroundBiological advantage of color vision for primate is the ability to detect colorful objects in the wild o Adaptation helps with foraging for fruit in the bushes and treesThe ability to perceive color is an important advantage foro Detecting predators or prey against a background o Determining ripeness of fruit o The richness of the soil o Using the color of sunsets as a means to predict weatherThe Functions of Color Vision in Different Species o Color vision is important in nonmammalian specieso Many birds fish and insects are able to see colors that humans dont seeColors at the UV end of the spectrum o Mating BehaviourBirdscolor of potential mates colors indicates health and can influence the likelihood of choosing that mate o ForagingBeessome flowers have adapted patterns on the petals that are invisible to humans but serve as nectar maps to the beeColor MixingPrimary Colorsthe three colors that can be combined in various proportions to make every color in the spectrum o Base colors cannot be reduced into other colorsTwo types of color mixing additive and subtractiveSubtractive Color Mixingwhen colored pigments selectively absorb some wavelengths and reflect others o Primary colors are red blue and yellow o Mixing of pigments dyes or paints o Subtractive because every reflective surface absorbs or subtracts the colors that it does not reflect o Adding other pigments to the surface alters the combination wavelengths subtracted o Eg Blue objectslooks blue because all wavelengths are being absorbed by the object except short blue waves o When two pigments are mixed all wavelengths are being absorbed except those that the two pigments jointly reflect o Eg Shine white light through a yellow then a blue filtersee greenWhen the light hits the yellow filterall the short waves blue and purples are absorbed subtracted out only longer green yellow orange and red waves are allowed to pass throughWhen these waves hit the blue filterabsorbs the longest waves yellow orange and red What is left over is a middle band of wavelengths that is transmitted by both pigmentsgreen 1 Video LecturePsych 1XX3 o Complementary ColorsIf you mix a primary color with its complementary coloryou get brown RedGreenBlueOrangeYellowPurpleAdditive Color Mixingwhen colored lights add their dominant color to the mixtureo How our visual system processes colorby adding the effects of different wavelengths together in our nervous system o Primary colors are red green and blue o Complementary Colorsdifferent than in subtractive If you mix a primary color with its complementary coloryou get grey or whiteRedBluishGreenGreenReddish Purple BlueYellowo Eg Blue and yellow filteroverlap colored lights from each one onto the reflective surface Each colored light adds its dominant wavelength to the mixtureFind that now blue and yellow do not make greenmakes greyo Eg Magnify a yellow patch on your TV screenfind that theyre tiny green and red dotsTheories of Color VisionTrichromatic Theoryproposes that the retina contains three different kinds of cones receptors that are each maximally sensitive to different wavelengths of light oYoungHelmholtz TheoryFirst proposed by Thomas Young in 1803Modified by Hermanvon Helmholtz in 18662
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