Chapter 6 Notes
Chapter 6 Notes Psyc 2010-003
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This 8 page Class Notes was uploaded by Alise Robison on Sunday February 28, 2016. The Class Notes belongs to Psyc 2010-003 at Clemson University taught by Chong Hyon Pak in Winter 2016. Since its upload, it has received 44 views. For similar materials see Introduction to Psychology in Psychlogy at Clemson University.
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Date Created: 02/28/16
Chapter 6: Sensation and Perception How do we construct our representations of the external world? Sensation: detect physical energy (a stimulus) from the environment and convert it into neural signals o The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment Perception: when we select, organize, and interpret our sensations o The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events Bottom-up processing: analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind (the brain’s integration of sensory information) Top-down processing: information processing guided by higher- level mental processes, as when we construct perceptions drawing on our experience and expectations Transduction: conversions of one form of energy into another o In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret Psychophysics: the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them Thresholds Absolute threshold: the minimum stimulation needed to detect a particular stimulus 50% of the time Signal detection theory: a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) o Assumes there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and alertness Subliminal: below one’s absolute threshold for conscious awareness Priming: the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response Difference threshold: the minimum difference between two stimuli required for detection 50% of the time o We experience the difference threshold as a just noticeable difference Weber’s law: the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount) Sensory adaptation: diminished sensitivity as a consequence of constant stimulation Perceptual set: a mental predisposition to perceive one thing and not another Vision Light’s physical properties are perceived in specific ways o Wavelength: hue (color) o Amplitude: power or intensity (brightness) of the radiant energy Wavelength: the distance from the peak of one light or sound wave to the peak of the next o Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission o Meters or nanometers o Short: violet o Long: red Hue: the dimension of color that is determined by the wavelength of light (blue, green, red, etc.) Intensity: the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave’s amplitude Eye Pupil: the adjustable opening in the center of the eye through which light enters Iris: a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening o Responds to light intensity or internal states Lens: the transparent structure behind the pupil that changes shape to help focus images on the retina in a process called accommodation Retina: the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information o A layer of photo-sensitive cells in the back surface of the eyeball o The retina transduces photons into chemical changes that result in neural impulses Ganglion: highly aggregated (summarized) information from thousands of visual receptors are fed into the ganglion o “Sees” a small part of the world—their “receptive field” Optic nerve: the nerve that carries neural impulses form the eye to the brain Blind spot: the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there Fovea: the central focal point in the retina, around which the eye’s cones cluster Rods: retinal receptors that detect black, white, and gray o Necessary for peripheral and twilight vision, when cones don’t respond o Distributed all over retina o Primarily responsible for peripheral vision and vision in the dark Cones: retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions o Detect fine detail and give rise to color sensation o Concentrated on fovea o Primarily responsible for detection of detail and color Visual Information Processing In the journey from retina to brain, information is processed, abstracted many times, at all levels Feature detection: nerve cells in the visual cortex respond to specific features of the stimulus, such as shape, angle, edges, or movement o Shape detection: specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs, and houses Parallel processing: the processing of many aspects of a problem simultaneously o Brain’s natural mode of information processing for many functions, including vision o Contrasts with step-by-step (serial) processing of most computers and of conscious problem solving o Brain divides a visual scene into subdivisions such as color, depth, form, movement, etc Young-Helmholtz trichromatic (three-color) theory: the theory that the retina contains three different color receptors (red, green, blue) which, when stimulated in combination, can produce the perception of any color o Three types of cones, each type is most sensitive to particular wavelengths o Red cones, blue cones o Color blindness: genetic disorder in which people are blind to green or red colors, supporting trichromatic theory o Problem: The trichromatic theory cannot explain some quirks of color vision, such as afterimages (think of flag and bee) Red-green color blind people can see yellow… shouldn’t be possible Yellow seems to be a pure color like red, green, and blue Opponent-process theory: the theory that opposing retinal processes enable color vision o Visual elements sensitive of color are grouped into three pairs, whose members oppose or inhibit each other Red-green, blue-yellow, black-white Explains phenomenon of complimentary colors (think of flag) Both theories are correct, color processing happens in two stages o At the retina, you have three types of cones (trichromatic theory) o At ganglion cells, there are receptors paired among complimentary colors (opponent-processing theory) Phi phenomenon: an illusion of movement created when two or more adjacent lights blink on and off in quick succession Perceptual constancy: perceiving objects as unchanging (having consistent shapes, size, brightness, and color) even as illumination and retinal images change Color constancy: perceiving familiar objects as having consistent color, even if changing illumination alters the wavelength reflected by the object Perceptual adaptation: in vision, the ability to adjust to an artificially displaced or even inverted visual field Hearing Audition: the sense or act of hearing Frequency: the number of complete wavelengths that pass a point in a given time (for example, per second) Pitch: a tone’s experienced highness or lowness; depends on frequency Loudness: determined by the amplitude, or height, of the sound wave Middle ear: the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window Cochlea: a coiled, bony, fluid-filled tube in the inner ear o Sound waves traveling through the cochlear fluid trigger nerve impulses o Transduction occurs here Cochlear implant: a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea Inner ear: the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs Sensorineural hearing loss: hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves o Also called nerve deafness Conduction hearing loss: hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea Overview of the Sensation of sound: mechanical energy converted into electrical activity (neural impulses) Sound waves collected by auditory structures (ear, tympanic membrane) Transduction via cochlea (movement of hair in the basilar membrane) Neural signals sent to brain via auditory nerve How we code pitch sound Place theory: in hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated o Hair cells at a particular place on the basilar membrane respond to a particular frequency of sound o Which place responds o Best dscribes how we hear high frequencies o Cant easily explain low frequency Frequency matching theory: in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of tone, thus enabling us to sense its pitch o Firing rate of an auditory nerve matches the sound waves frequency o Best describes how we hear low frequencies Other Senses/Perceptual Organization Touch and Pain Nociceptors: sensory receptors that detect hurtful temperatures, pressures, or chemicals Gate-control theory: the theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain o The “gate” is opened up by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by info coming from the brain Taste Taste receptors are concentrated on the tongue—papillae Receptors only discriminate 5 sensations o Salty, sour, sweet, bitter, umami (meaty taste) Sensory interaction: the principle that one sense may influence another, as when the smell of food influences its taste Embodied cognition: in psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments Smell (olfaction) Has direct link to amygdala—memory Only sense that does NOT send messages through the thalamus o Axons from neurons in the nose have synapse in olfactory bulb o Connections in the olfactory bulb are plentiful in the amygdala Body Position and Movement Kinesthesis: the system for sensing the position and movement of individual body parts Vestibular sense: the sense of body movement and position, including the sense of balance Summary of Senses Vision—light waves striking the eye—rods and cones in the retina Hearing—sound waves striking the outer ear—cochlea hair cells in the inner ear Touch—pressure, warmth, cold on skin—skin receptors detect pressure, warmth, cold, and pain Taste—chemical modules in the mouth—basic tongue receptors for sweet, sour, salty, bitter, and umami Smell—chemical molecules breathed in through the nose— millions of receptors at top of nasal cavity Body position (kinesthesis)—any change in position of a body part, interacting with vision—kinesthesis sensors all over the body Body movement (vestibular sense)—movement of fluids in the inner ear caused by head/body movement—hairlike receptors in the semi-circular canals and vestibular sacs Perception How do we perceive different objects in the environment? Taking raw sensation and adding meaning from our knowledge and experience of the world Gestalt: an organized whole o Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes Figure-ground: the organization of the visual field into objects (the figures that have meaning) that stand out from their surroundings (the ground that doesn’t have meaning) o Edges determine figure/ground border Perceptual Grouping: the perceptual tendency to organize stimuli into coherent groups Gestalt’s Law of Organization (top down) The whole is greater than the some because we add meaning What properties of stimuli cause us to group them together? o Proximity: things that are close together will be grouped together o Similarity: things that look similar o Continuity: things smoothly connected are perceived as one o Closure: even though it has gaps, you connect it o Common region o Connectedness Depth perception: the ability to see objects in three dimensions although the images that strike the retina are two-dimensional Allows us to judge distance How do we perceive 3D from 2D image projected by the retina? Depth cues Visual cliff: a laboratory device for testing depth perception in infants and young animals Retinal disparity: a binocular cue for perceiving depth o By comparing images from the retinas in the two eyes, the brain computes distance The greater the disparity (distance) between two images, the closer the object Monocular cues: depth cues, such as interposition and linear perspective, available to either eye alone o (One eye) exist in environment o Interposition (occlusion): something blocks something else o Relative size o Height in visual field o Textural gradient—smoothness, roughness o Linear perspective: parallel lines are not parallel—reach to a focal point at the horizon o Reduced clarity o Light and shadow Binocular cues: depth cues, such as retinal disparity, that depend on the use of two eyes o (Two eyes) generated by you o Accommodation: information about muscle activity involved in accommodation serves as one cue o Convergence: depth cue resulting from rotation of eyes so that the image can be projected on each retina o Binocular disparity: cue based on the difference between retinal images received by each eye
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