Chapter 3 2 19 13 6 on Concept Sheet Structures of the Eye Iris a muscle that dilates and constricts to make the pupil smaller or bigger Pupil empty space that allows light in to hit the retina Cornea a protective layer over the entire eyeball Lens focusing light coming from the outside world onto the back part of the eye is a form of organic flexible glass allows us to focus on things far away and close up Accommodation automatic adjustment of the lens to focus on things far away and close up Retina part of the eye filled with specialized neurons that converts light energy to electrochemical impulses that are sent to the brain Transduction the transformation of energy 7 on Concept Sheet Rods 100 120 million Very sensitive to small amounts light Only register shades of gray Directly responsible for black in white vision and night vision Not in fovea Cones 5 6 million Sensitive to particular wavelengths Produce color vision Denser near fovea Dark Adaptation 8 on Concept Sheet Color Vision Trichromatic Theory theory that possessing three independent channels for conveying color information derived from the 3 different cone types Opponent process theory if a particular color is present it causes cells that recognize it to inhibit the perception of the complimentary color red green and blue yellow Afterimage when you re exposed to a bright blue light after that blue light is taken away you ll see yellow Opponent cells Color blindness Primary colors of light Red Blue Green 9 on Concept Sheet Organizing the Visual World Perceptual organization Phase 1 o Proximity o Continuity o Similarity o Closure o Good Form o You have a part that figures out edges o You have a part that figures out what is in the foreground figure background Gestalt Laws of Organization ambiguous figures more than one visual interpretation Subjective contours perceiving contours or lines where none exist 10 on Concept Sheet Perceptual Constancies the perception of characteristics that occurs when an object is assumed to remain the same even though sensory information striking the eyes changes Size constancy we still assume objects retain their size Shape constancy just because how you re looking at something in a different way we believe it s still the same shape Color constancy when we see a blue shirt when we turn the lights off and it now appears darker we believe it is still the same color blue 11 on Concept Sheet Knowing the Distance Visual cues Problem the 3 D world is projected onto a 2 D retina o How do you construct a 3 D perception based on 2 D retinal images o Ex Accommodation o Static Cues visual cues of objects that aren t moving Binocular Cues require the use of both eyes working together they are our best most accurate source of depth perception of distances under 20 feet Retinal disparity involves the difference of the images on the two eyes on an object the closer it gets to you Convergence at distances less than 20 feet the closer something is to you the more your eyes have to cross to both focus on it then your brain judges depth and distance based on the amount that your eyes are crossed Monocular cues require the use of only one eye Texture gradient the part of the picture that is detailed versus the part of the picture that is fuzzy we see the detailed part as being closer to us Allow you to see the position of objects relative to other objects o Motion Cues visual cues of objects that are moving Motion parallax images of objects at different distances move across the retina in different speeds o Things close to you fly by you and things far away from you look like they re barely moving When either objects are moving past you or you re moving past objects 12 on Concept Sheet Visual Perception Pathways Knowing More Than You can See Bottom up processing perception triggered only by the visual stimulus analyzing something for the first time Top down processing recognition based on experience making assumptions Perceptual set your entire set of assumptions and beliefs about the perceptual world a form of top down processing 13 on Concept Sheet Attention The Gateway to Awareness Perception is attention Selective attention o Pop out bottom up o Vigilance top down o Stroop effect