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PSYB51H3 (306)
Chapter 5

Chapter 5 - study notes

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Department
Psychology
Course
PSYB51H3
Professor
Matthias Niemeier
Semester
Fall

Description
CHAPTER 5: PERCEPTION OF COLOR Describe one experiment that would suggest that faces arent special. Wat were ps asked to do? Which method was used? Wat was found? Wat does that potentially mean? Greebles experiment. Where ps were trained to recognize greebles, (new figures). And results show that (they used fmri) that increase activity in fissform phase area, and this might meant tat we are lookin at area in brain that not specialized in faces but for any kinda of visual expertise. BASIC PRINCIPLES OF COLOUR PERCEPTION -color is not a physical property of things , it is creation of mind. Visible spectrum run from 400-700nm. Most light tat we see is reflected light. The more light that is absorbed, the darker surface will appear. Colour of surface depends on mix of wavelengths that reach eye from the surface. Specific wavelengths of light are NOT specific colours. Color is the result of interaction of a physical stimulus with a particular nervous system PROBLEM OF UNIVARIANCE -a single photoreceptor shows diff responses to lights of diff wavelengths but the same intensity. With wavelengths as x-axis and receptor response as y axis, we see inverted U curve. There are 2 pts in the wavelength where the photoreceptors have the same response. So if we were looking at the output of photoreceptors only, we would have no way of distinguishing b the 2 lights. But when we look with a normal human colour vision system, we can see that wavelength A and B are so and so colour - note that intensity can be reduced. ie the photoreceptors response rate, the highest one, can be reduced to match the 2 pts in the U curve that had the same response rate. So when it comes to seeing colours, the output of a single photoreceptor ie the photoreceptors response is completely ambiguous. An infinite set of different wavelength and intensity combinations can elicit exactly the same response. So output of a single photoreceptor cant by itself tell us anything about the wavelengths stimulating it. =problem of univariance = one photoreceptor type cant make colour discriminations based on wavelength TRICHROMACY RODS AND CONES - 2 kinds of photoreceptors: rods and cones. Rods sensitive to low, scotopic, light levels. All rods contain the same type of photopigment molecule: rhodopsin thus they all have same sensitivity to wavelength. Consequence, thought rods able to tell light from dark under scotopic conditions, problem of univariance make it not possible to discriminate colors. This is hint that color is psychophysical and not physical . at night, dim light stimulate only rods and they only have 1 kind so cant tell colours apart www.notesolution.com
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