PSYCHOLOGY 2010 H 3 SENSATION AND PERCEPTION 1 Definitions Kowalski a Sensation the detection or awareness of changes in physical energy produced by environmental or internal event i Stimulus must be appropriate for the sensory system e g light for vision sound for how the brain interprets or organizes what you sense conversion of one thing into something else in this case the conversion d Absolute Threshold minimal amount of physical energy stimulation needed for an e Difference Threshold lowest level of stimulation required to sense that a change in smallest difference in intensity between 2 stimuli that tendency of sensory systems to respond less to stimuli that continue hearing b Perception c Transduction of physical energy into neural activity observer to notice a stimulus stimulation happened i Just Noticeable Difference people detect f Sensory Adaption without change Importance of senses a Evolved to help us survive 2 3 Vision a Parts of the Eye and their functions Outer covering of i Sclera the eye 1 Forms the cornea in the front transparent part bends and ii Cornea focuses light provides nutrients to the cornea and carries away waste ring of pigmented fibers gives the eye it s color muscle fibers cause pupil to iii Aqueous Humor iv Iris constrict or dilate thus controlling the amount of light let in amount of light let in 1 The smaller the pupil the sharper the vision v Pupil opening in the center of the iris that constricts or dilates to regulate the a Parasympathetic Nervous System causes pupil to respond to illumination b Sympathetic Nervous System causes pupil to respond to emotions disk shaped elastic structure focuses light changes in the len s shape that focuses light rays provides nutrients to the lens helps the eye keep it s shape light sensitive layer of tissue at back of eye Transforms light to neural photoreceptors Key role in night vision and peripheral vision process by which the eyes become more sensitive to light 2 Cones photoreceptors Key role in daylight vision and color vision process by which the eyes become less sensitive to light vi Lens 1 Accommodation vii Vitreous Humor viii Retina impulses 1 Rods a 120 million rods b Dark Adaptation in low illumination a 7 million cones b Light Adaptation in high illumination 3 Fovea central region of the retina where light is mostly directed focused by ix Optic Nerve 1 Blind spot bundle of axon and ganglion cells Carries info from retina to brain point of retina where optic nerve leaves eye and contains no receptor lens cells b Inattentional Blindness c Depth Perception i Perceive depth through not seeing things that are really there organization of perception in 3 dimensions 1 Organismic Cues used to perceive depth over short distances a Accommodation lens Focus on something near the lens bulges feedback from the muscles that control the shape of the b Convergence your eyes converge when you look at something near gets smaller as the image moves away from you c Retinal image size i Emment s law the size of the retinal image and the distance of an object are inversely related d Binocular disparity are several inches apart Brain fuses two images each eye has a slightly different image because they 2 Environmental Cues used to perceive depth over longer distances closer objects conceal further objects parallel lines converge as they go off in the distance patterns become dense as they recede into the distance a Linear perspective b Interposition c Texture gradients d Aerial haze e Motion parallex further away i objects between you and fixation appear to move in the opposite direction near objects appear to move faster than objects that are far away objects become hazier 1 Trichromatic Theory Young Helmholtz Theory eyes contain 3 receptors blue red green with different sensitivities to different wavelengths of light a Perceptions of all colors are produced through the combinations of activity of these 3 receptors 2 Opponent Process Theory green a The colors work in pairs red green blue yellow black white existence of 4 primary colors red blue yellow i Opposing colors cannot be coded at the same time 1 Opponent process cells that are inhibited by a particular color produce a burst of firing when the color is removed a Causes an Afterimage 3 Proponents of both theories a Perception of color involves sequential stages of information processing i Receptors that do the first stage follow trichromatic theory ii Color Vision a Different perceptions psychological reality of the same object physical reality comes 4 Perception from a peoples minds i What you perceive depends on 1 The physical stimulus 2 The physiological system 3 Other characteristics of the person experience knowledge 4 Motivation ii Psychophysics psychological stimulus 1 Detection means used to study the relationship between physical and 2 Discrimination what is the smallest difference that can be perceived between 2 what is the least amount of stimulus required to produce a sensation a Absolute Threshold is the answer stimuli a Difference threshold or just noticeable difference is the answer