Sensation _ Perception - lecture 12 - theories of color vision

Sensation _ Perception - lecture 12 - theories of color vision

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Lecture 12 Theories of Color Perception
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Color
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Evolution of Color Vision Common assumption is that the evolution of color vision was progressive from black and white to dichromatic to trichromatic vision. Even as a "thought experiment," it would seem unlikely that rod cells preceded the earliest cone cells. Rods are more sensitive to and become “bleached” when exposed to light. Evidence suggests that rod cells are derived from cone cells.
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Evolution of Color Vision At some stage along the path – say 800 million years ago on a Wednesday afternoon following a small lunch – some multi-cell organisms managed to develop photoreceptors that gave them the ability to detect and respond to some form of light. What are the benefits?
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Evolution of Color Vision Having even a rudimentary form of vision obviously conveyed a tremendous evolutionary advantage … Gives one the ability ability to sneak up on your visionless contemporaries, tap them on the shoulder, and shout "Boo!" (or you could simply eat them if you weren't feeling in a party mood.)
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Evolution of Color Vision However… Having only one type of cone cell means that you're limited to seeing only a small portion of the electromagnetic spectrum. If visual capabilities can be extended to encompass additional portions of the spectrum, this will convey an even greater evolutionary advantage.
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Properties of Color Physical Properties Psychological Correlate Wavelength Purity Reflectance Intensity Hue Saturation Lightness Brightness
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Properties of Color Hue Psychological reactance to wavelengths ranging from approximately 400 nm (violet) to 700 nm (red). Essentially “the color” of something … what we see and experience.
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Properties of Color Saturation Psychological correlate of purity.
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“Purest” color you can get corresponds to a monochromatic or spectral hue. Adding other wavelengths of white light
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Sensation _ Perception - lecture 12 - theories of color vision

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