Chapter 8

Chapter 8 - Chapter 8 Study Guide Psychology 101 Chap 8...

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1 Chapter 8 Study Guide Psychology 101 Chap 8 (263-301) The Psychology of Vision 1.Through what steps might sophisticated eyes like ours have evolved from primitive beginnings? 1. photoreceptors became concentrated into groups making eye spots on animals skin 2. eye spots recessed into pits to reduce glare 3. membrane over pits to protect from sand/debris 4. mutations thickened center to lens which became able to project an image onto the lining of photoreceptors 2. How do cornea, iris, and lens help form images on the retina? Cornea- transparent tissue that helps focus light that passes through it by its convex curvature Iris- opaque so only light can enter through pupil @ its center; muscles in it allow it to increase or decrease in diameter of the pupil to allow more or less light to enter Lens- becomes more spherical when focusing on objects close to the eye and flatter when focusing on those farther away Cornea and lens bring light rays together @ point on retina 3. How are comes and rods distributed on the retina, and how do they respond to light? Cones: permit sharply focused color vision in bright light- concentrated in the fovea= pin head size area of retina that is in the most direct line of sight Rods: permit vision in dim light, found everywhere but the fovea, more rods than cones 4. How do cone vision and rod vision differ? Cone vision (photopic vision)- high acuity and color perception Rod vision (scotopic) – specialized for sensitivity, ability to see in dim light 5. What is the chemical basis for dark adaptation and light adaptation? Iris dilates the pupil in dim light and constricts it in bright light Why do we see mostly with cones in bright light and with rods in dim light? Rhodopsin, the rod photochemical, is more sensitive to light than cone photochemicals; bright light breaks the rhodopsin down into inactive substances so they can’t function
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1 Chapter 8 Study Guide Psychology 101 6. How does the pattern of neural connections within the retina help account for the greater sensitivity and reduced acuity of rod vision compared with cone vision? Convergence from rods, to bipolar cell, to ganglion cell increases sensitivity of rod vision in dim light by adding the output of many rods to generate activity in the ganglion cells – like a funnel collecting from a wide area and channeling into a single stream. This neural convergence decreases acuity by activating only one ganglion cell. There is little convergence in the fovea where the cones are. This results in reduced sensitivity to dim light, because there is no funneling activity, but high acuity bec each spot of visual stimulation activates a separate pathway to brain. 7. How can light be described physically, and what is the relationship of its wavelength to its perceived color? By particles and waves: the particles are photons- individual packets of light
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Chapter 8 - Chapter 8 Study Guide Psychology 101 Chap 8...

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