Topic #6 - Sensation (Vision & Pain) and Perception

Topic #6 - Sensation (Vision & Pain) and Perception -...

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Psy1101  Introduction to Experimental Psychology Prof. K. Campbell Sensation & Perception
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Introduction to Experimental Psychology Sensation: Vision   Physics of light Electromagnetic signal whose wavelength varies from 400 to 700 nanometers (this is  called "light"). Short wavelengths (400-500 nm = violet-blue); Medium wavelengths  (500-600 nm = green); Long wavelengths (600-700 nm = red). We thus perceive only a  very limited amount of the electromagnetic energy in the universe (from 10 -5  to 10 15  nm). Colour. The wavelength of the light determines its physical hue which we perceive  psychologically as “colour” Brightness. The amount of energy in the light wave (or its intensity) is perceived as  “brightness”.    Anatomy of the Eye   The Eye Cornea Lens Pupil Retina: rods and cones; fovea; blind spot
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The Retina The retina consists of 3 layers The rods and cones The bipolar cells The ganglion cells The light sensitive rods and cones are located in the back of the retina Light must thus pass through the other layers before striking the rods and cones The rods and cones have a chemical reaction to light. If the reaction is strong enough, the bipolar cells will be activated Bipolar cells activate the ganglion cells The axons of the ganglion cells converge at the “blind spot” to form the optic nerve.   The Cones
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Cones - packed in the centre of the retina, near the fovea (where vision is most acute  -- “acuity”) Colour vision: three types of cones -- for red, green, blue A single cone may project to a single bipolar cell. Thus, the output of the cone will  have to be very high in order for the bipolar cell to be activated.  Need a great deal of  light to see in colour. The Rods Rods - in the periphery. There are many fewer rods than cones.  Excellent for detecting movement.  Not sensitive to colour Several rods project to a single bipolar cell. Thus,  sensitive to very low levels of  light.   Sensitivity of rods and cones. The rods are much more sensitive than the cones.  Therefore, in order to see colour, the light must be relatively intense. On the other  hand, the rods are able to detect light at very low intensities. The rods are therefore  used for "night" vision. Logically, we do not see colours well in darkness.  
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This note was uploaded on 12/21/2010 for the course PSY 1101 taught by Professor Textbook during the Fall '08 term at University of Ottawa.

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Topic #6 - Sensation (Vision & Pain) and Perception -...

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