Chapter 4 PSYC 101 003
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This 7 page Class Notes was uploaded by Marika O'Hara on Tuesday September 20, 2016. The Class Notes belongs to PSYC 101 003 at University of North Carolina - Chapel Hill taught by Frederick Wiss in Fall 2016. Since its upload, it has received 3 views. For similar materials see Introduction to Psychology in Psychology (PSYC) at University of North Carolina - Chapel Hill.
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Date Created: 09/20/16
Chapter 4 - Sensation and Perception Sunday, September 18, 2016 9:57 AM • Sensation: the stimulation of sense organs • Perception: the selection, organization and interpretation of sensory input • Sensation involves the absorption of energy like light and sound waves by the eyes or ears • Perception is organizing and translating sensory information into something meaningful The Visual System: Essentials of Sight The Stimulus: Light • Light: a form of electromagnetic radiation that travels as a wave, moving at the speed of light • Light waves vary in amplitude and wavelength ○ Amplitude affects the perception of brightness ○ Wavelength affects the perception of color • Light can vary in urity: how varied the mix of different wavelengths is ○ Purity affects saturation: the richness of colors ○ Saturation: the relative amount of whiteness in a color The Eye: A Living Optical Instrument • Eyes channel light to the neural tissues that receive (tinand house that tissue • Light enters the eyes through thc ornea: a transparent window at the front • Lens: a transparent eyes structure that focuses the light rays falling on the retina • Accommodation occurs when the curvature of the lens adjusts to alter visual focus • Most visual problems are caused by focusing problems or defects in the lens ○ Nearsightedness: when close objects are seen clearly but distant objects appear blurry because the focus of light from distant objects falls short of the retina ○ Farsightedness: distant objects are seen clearly but close objects appear blurry because the focus of light from close objects falls behind the retina • Pupil: the opening in the center of the iris that helps regulate the amount of light passing into the rear chamber of the eye ○ When the pupil constricts, it lets less light into the eyes, but it sharpens the image Farsightedness: distant objects are seen clearly but close objects appear ○ blurry because the focus of light from close objects falls behind the retina • Pupil: the opening in the center of the iris that helps regulate the amount of light passing into the rear chamber of the eye ○ When the pupil constricts, it lets less light into the eyes, but it sharpens the image ○ When the pupil dilates, it lets more light in but the image is less sharp The Retina: The Brain's Envoy in the Eye • Retina: the neural tissue linking the inside back surface of the eyes that absorbs light, processes images, and sends visual information to the brain • Each eye has a blind spot and the brain somehow fills in the missing part of the image VISUAL RECEPTORS: RODS AND CONES • Rods outnumber cones about 20:1 • Cones: specialized visual receptors that play a key role in daylight vision and color vision ○ Cones don't respond well to dim light which is why you don't see color well in dim light ○ Cones provide better sharpness and precise detail than rods ○ Fovea: a tiny spot in the center of the retina that contains only cones § Visual acuity is greatest at this spot • Rods: specialized visual receptors that play a key role in night vision and peripheral vision Rods are 100 times more sensitive to dim light than cones ○ DARK AND LIGHT ADAPTION • Dark adaption:t he process in which the eyes become more sensitive to light in low illumination • Light adaption:t he process in which the eyes become less sensitive to light in high illumination INFORMATION PROCESSING IN THE RETINA • The retina transforms a pattern of light falling onto it into a very different representation of the visual scene • Receptive field of a visual cel: e retinal area that, when stimulated, affects the firing of that cell • Receptive fields come in various shapes and sizes Vision and the Brain VISUAL PATHWAYS TO THE BRAIN • Optic chiasm: the point at which the axons from the inside half of each eye cross over and then project to the opposite half of the brain ○ Ensures that signals from both eyes go to both hemispheres of the brain INFORMATION PROCESSING IN THE VISUAL CORTEX • Visual input ultimately arrives in the primary visual cortex located in the occipital lobe. • Optic chiasm: the point at which the axons from the inside half of each eye cross over and then project to the opposite half of the brain ○ Ensures that signals from both eyes go to both hemispheres of the brain INFORMATION PROCESSING IN THE VISUAL CORTEX • Visual input ultimately arrives in the primary visual cortex located in the occipital lobe. • The cells in the visual cortex are highly specialized • Feature detectors: neurons that respond selectively to very specific features of more complex stimuli • After visual input is processed in the primary visual cortex, it is often routed to other cortical areas for additional processing ○ Travel through "what" and "where" pathways • Ventral stream: processes the details of what objects are out there • Dorsal stream:p rocesses where the objects are Viewing the World in Color • Some believe that color vision evolved in humans and monkeys because it made it easier to find food THE STIMULUS FOR COLOR • There are two kinds of color mixture: subtractive and additive ○ Subtractive color mixing orks by removing from wavelengths of light, leaving less light than was originally there ○ Additive color mixingworks by superimposing lights, putting more light in the mixture than exists in any one light by itself • Human processes of color perception parallel additive mixing more closely than subtractive mixing TRICHROMATIC THEORY OF COLOR VISION • Trichromatic theoryh : olds that the human eye has three types of receptors with differing sensitivities to different light wavelengths ○ The eye contains specialized receptors sensitive to the wavelengths associated with red, green, or blue • Color blindness: encompasses a variety of deficiencies in the ability to distinguish among colors ○ Color blindness occurs more frequently in males than females OPPONENT PROCESS THEORY OF COLOR VISION • Complementary colorsp : airs of colors that produce gray tones when mixed together • Afterimage: a visual image that persists after a stimulus is removed ○ The color of the afterimage with be the complement of the color who originally stared at ○ Trichromatic theory cannot account for the appearance of complementary afterimages • Opponent process theory: holds that color perception depends on receptors that make antagonistic responses to three pairs of colors ○ The color of the afterimage with be the complement of the color who originally stared at ○ Trichromatic theory cannot account for the appearance of complementary afterimages • Opponent process theory: holds that color perception depends on receptors that make antagonistic responses to three pairs of colors RECONCILING THEORIES OF COLOR VISION • Perception of color appears to involve stages of information processing • The receptors that do the first stage of processing follow trichromatic theory • Cells in the retina and the brain seem to follow opponent process theory Effects of Color on Behavior • Colors can have automatic, unconscious effects on behavior which are rooted in the evolutionary significance of certain colors The Visual System: Perceptual Processes Perceiving Forms, Patterns, and Objects • The same visual input can result in radically different perceptions • Perceptual set: a readiness to perceive a stimulus in particular way ○ Creates a certain slant in how you interpret sensory input • Form perception depends on the selection of sensory input - what people focus their attention on • Inattentional blindness: the failure to see fully visible objects or events in a visual display because one's attention is focused elsewhere FEATURE ANALYSIS: ASSEMBLING FORMS • Feature analysis: the process of detecting specific elements in a visual input and assembling them into a more complex form • Bottom-up processing: a progression from individual elements to the whole • Top-down processing: a progression from the whole to the elements LOOKING AT THE WHOLE PICTUREL GESTALT PRINCIPLES • Phi phenomenon: the illusion of movement created by presenting visual stimuli in rapid succession • Figure and Ground ○ People organize visual perceptions by dividing visual displays into figure and ground • Proximity ○ Things that are near one another seem to belong together • Closure ○ People group elements to create a sense of closure or completeness • Similarity ○ People tend to group stimuli that are similar • Continuity ○ People tend to connect points that result in straight or gently curved lines • Closure ○ People group elements to create a sense of closure or completeness • Similarity ○ People tend to group stimuli that are similar • Continuity ○ People tend to connect points that result in straight or gently curved lines FORMULATING PERCEPTUAL HYPOTHESES • Perceptual hypothesis: an inference about what form could be responsible for a pattern of sensory stimulation Perceiving Depth or Distance • Depth perceptioni : volves interpretation of visual cues that indicate how near or far away objects are • To make judgments of distance, people rely on binocular and monocular cues ○ BINOCULAR CUES § Binocular depth cuesc: lues about distance based on the differing views of the two eyes § Retinal disparityt he fact that objects within 25 feet project images to slightly different locations on the right and left retinas, so left and right eyes see slightly different views of the object ○ MONOCULAR CUES § Monocular depth cues: clues about distance based on the image in either eyes alone § Pictorial depth cues: cues about distance that can be given in a flat picture • Some cultural differences may exist in the ability to take advantage of pictorial death cues in 2D drawings • Estimates of distance can be skewed by people's motivational states ○ People see desirable objects as being closer to them than less desirable objects Perceptual Constancies in Vision • Perceptual constancy: a tendency to experience a stable perception in the face of continually changing sensory input • Someone's image grows in our retinas as they get closer to us but we don't perceive them as growing in size in front of us The Power of Misleading Cues: Visual Illusions • Visual illusion: an apparently inexplicable discrepancy between the appearance of a visual stimulus and its physical reality The Auditory System: Hearing The Stimulus: Sound • Sound waves are characterized by their wavelength, amplitude, and purity ○ These properties affect their perceived pitch, loudness, and timbre. Human Hearing Capacities The Auditory System: Hearing The Stimulus: Sound • Sound waves are characterized by their wavelength, amplitude, and purity ○ These properties affect their perceived pitch, loudness, and timbre. Human Hearing Capacities • Wavelengths of sound are described in terms of their frequency ○ Frequency is measured in cycles per second - hertz ○ Higher frequencies will have higher pitches • People can hear only a portion of the available range of sounds • The greater the amplitude of sound waves, the louder the sound is perceived ○ Amplitude is measured in decibels • The purest sound is one that has only a single frequency of vibration (ex. Tuning fork) ○ Most sounds have a combination of frequencies Sensory Processing in the Ear • External ear depends in vibration of air molecules ○ External ear contains tp inna: a sound-collecting cone • Middle ear depends on the vibration of movable bones • Inner ear depends in waves in a fluid ○ These are converted into a stream of neural signals sent to the brain ○ Cochlea: a fluid-filled, coiled tunnel that contains the receptors for hearing ○ Basilar membrane: r uns the length of the spiraled cochlea and holds the auditory receptors (hair cells) Auditory Perception: Theories of Hearing PLACE THEORY • Place theory: holds that perception of pitch corresponds to the vibration of different portions, or places, along the basilar membrane FREQUENCY THEORY • Frequency theory: holds that the perception of pitch corresponds to the rate, or frequency, at which the entire basilar membrane vibrates The Other Senses: Taste, Smell, and Touch • Gustatory system: the sensory system for taste Taste: The Gustatory System • Gustatory receptors: clusters of taste cells found in the taste buds • Four primary tastes ○ Sweet, sour, bitter, and salty • People vary in their sensitivity to certain tastes • Sensory adaptation: a gradual decline in sensitivity to prolonged stimulation Smell: The Olfactory System • Olfactory system:s ensory system for smell • Olfactory cilia: receptors for smell, hair like structures found in upper portion ○ Sweet, sour, bitter, and salty • People vary in their sensitivity to certain tastes • Sensory adaptation: a gradual decline in sensitivity to prolonged stimulation Smell: The Olfactory System • Olfactory system:s ensory system for smell • Olfactory cilia: receptors for smell, hair like structures found in upper portion of the nasal passages • Smell is the only sensory system that is not routed through the thalamus before it projects onto the cortex Touch: Sensory Systems in the Skin • Physical stimuli for touch are mechanical, thermal, an chemical energies that come into contact with the skin • Six different types of receptors are specialized for different functions (ex. Pressure, heat, cold, etc) • Pain perception is very subjective
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