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+ Chapter 5 Sensation James A. McCubbin, PhD Clemson University Worth Publishers Sensation Sensation a process by which our sensory receptors and nervous system receive and represent stimulus energy Perception a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events Sensation and Perception Paris in the the spring Sensation and Perception Sense Input Perception Sight colors/shapes object/event Hearing sound/noise words/music Touch pressure/temp feel of object Taste sour/salty/bitter/sweet flavor Smell spicy/resinous/burned odor rotten/fruity/flowery Perception Physiological variables: Receptors available Receptor limits Receptor abnormalities Sensory adaptation- diminished sensitivity as a consequence of constant stimulation Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it. Perception Psychological variables Interests Motivation Expectancy set Emotion Attitudes Values Gestaltists Gestalt means “whole” in German. The Gestaltists believed that people look to form patterns and complete whole images when they perceive things around them Sensation and Perception Sensation Our sensory and perceptual processes work together to help us sort out complex processes Sensation and Perception Perceptually Impaired Iti soft ennotre alized howcom plexT heproces sofrea ding is. Afe w sim plerear rang mentscan ha veyoucomp lete lycon f used! Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.” Sensation- Basic Principles Psychophysics study of the relationship between physical characteristics of stimuli and our psychological experience of them Light- brightness Sound- volume Pressure- weight Taste- sweetness Sensation- Thresholds Absolute Threshold minimum stimulation needed to detect a particular stimulus 50% of the time Difference Threshold minimum difference between two stimuli required for detection 50% of the time just noticeable difference (JND) Sensation- Thresholds Signal Detection Theory predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) assumes that there is no single absolute threshold detection depends partly on person’s experience expectations motivation level of fatigue Sensation- Thresholds 100 Percentage of correct detections Subliminal 75 50 Subliminal stimuli 25 0 Low Absolute threshold Intensity of stimulus Medium When stimuli are below one’s absolute threshold for conscious awareness Sensation- Thresholds Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage light intensity- 8% weight- 2% tone frequency- 0.3% Ex. A three way bulb Weber’s Law Vision Vision Pupil- adjustable opening in the center of the eye Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening Lens- transparent structure behind pupil that changes shape to focus images on the retina Retina’s Reaction to Light Optic nerve- nerve that carries neural impulses from the eye to the brain Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there Fovea- central point in the retina, around which the eye’s cones cluster Blind Spot Vision- Stabilized Images on the Retina Vision Transduction conversion of one form of energy to another in sensation, transforming of stimulus energies into neural impulses Wavelength the distance from the peak of one wave to the peak of the next Vision Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information Vision Acuity- the sharpness of vision Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina Vision Farsighted Vision Nearsighted Vision Normal Vision Vision Hue dimension of color determined by wavelength of light Intensity amount of energy in a wave determined by amplitude brightness loudness The spectrum of electromagnetic energy Vision- Physical Properties of Waves Short wavelength=high frequency (bluish colors, high-pitched sounds) Great amplitude (bright colors, loud sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds) Retina’s Reaction to Light- Receptors Rods peripheral retina detect black, white and gray twilight or low light Cones near center of retina fine detail and color vision daylight or well-lit conditions Photoreceptors E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969 Color-Deficient Vision People who suffer red-green blindness have trouble perceiving the number within the design Visual Information Processing Trichromatic (three color) Theory Young and Helmholtz three different retinal color receptors red green blue Afterimages Opponent ProcessAfterimage Effect Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON” “OFF” red green green red blue yellow yellow blue black white white black Pathways from the Eyes to the Visual Cortex Visual Information Processing Color Constancy Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object Feature Detection Ross Kinnaird/ Allsport/ Getty Images Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. How the Brain Perceives Illusory Contours Visual Information Processing Parallel Processing simultaneous processing of several aspects of a problem simultaneously The Ear Dr. Fred Hossler/ Visuals Unlimited The Ear Pinna- the external funnel shaped portion of the ear External Auditory Canal -directs sound waves to the eardrum Eardrum- thin piece of skin that vibrates to incoming sound Audition- The Ear Middle Ear chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window Inner Ear innermost part of the ear, contining the cochlea, semicircular canals, and vestibular sacs Cochlea coiled, bony, fluid-filled tube in the inner ear through which contains the cilia receptors for hearing on the basilar membrane. Audition Audition the sense of hearing Frequency the number of complete wavelengths that pass a point in a given time Pitch (measured in Hertz) a tone’s highness or lowness depends on frequency Audition Place Theory the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated Frequency Theory the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch How We Locate Sounds Location with Sound Doppler Shift- as something approaches the pitch is higher and as it recedes the pitch is lower. Ex. The train coming into the station. The Intensity of Some Common Sounds Audition Older people tend to hear low frequencies well but suffer hearing loss for high frequencies Amplitude required for perception relative to 20-29 year-old group 1 time 10 times 100 times 1000 times 32 64 128 256 512 1024 2048 4096 8192 16384 Frequency of tone in waves per second Low Pitch High Deafness Tinnitus- ringing in the ears when there is no external auditory stimulation caused by exposure to loud noise and represents damage to the auditory nerve. Deafness Conduction Hearing Loss hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea Nerve Hearing Loss hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve Deafness Choices in adjusting to hearing loss: Lip reading- family members and others must be careful to insure that their lips can be seen at all times during conversation American Sign Language- a set of symbols that represent words or phrases Cochlear Implant- an electrode is placed in the cochlea that artificially sends sound to the temporal lobe. Touch Skin Sensations pressure only skin sensation with identifiable receptors most on the hands and back of neck EX back vs. face 2pt. threshold warmth cold pain Touch Bruce Ayers/ Stone/ Getty Images The sense of touch is a mix of four distinct skin senses—pressure, warmth, cold, and pain. Skin Senses Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain. Pressure Burning hot Vibration Vibration Cold, warmth and pain Pain Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease exists in which the afflicted person feels no pain. AP Photo/ Stephen Morton Ashley Blocker (right) feels neither pain nor extreme hot or cold. Biopsychosocial Influences Gate-Control Theory Melzack and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed. Gary Comer/ PhototakeUSA.com Pain Gate-Control Theory theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain “gate” opened by the activity of pain signals traveling up small nerve fibers “gate” closed by activity in larger fibers or by information coming from the brain Pain State of mind can affect intensity of pain: WWI soldiers were relieved to be wounded to escape the terror of the battlefield. Athletes “play with pain” due to endorphins and realize the next day how they have injured themselves. Pain tolerance Touch There seems to a biological need for touch. Babies who are not touched suffer from “failure to thrive” which means they do not grow and eventually die. Premature babies in a study by Tiffany Field wear proven to benefit from daily massage and went home from the hospital sooner. In adults massage lowers cortisol levels and reduces the effect of stress. People in this culture have been “touch starved”. Body Position and Movement Kinesthesis the system for sensing the position and movement of individual body parts Proprioception-sense of the movement of muscles and tendons (body parts) in space. Vestibular Sense the sense of body movement and position including the sense of balance Taste Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called “Umami”. Sweet Sour Salty Bitter Umami (Fresh Chicken) Taste Taste Receptors Taste Taste Sensations sweet sour salty Bitter Some taste sensations are genetically programmed, such as sweet, and finding bitter and sour foods unpleasant A study of babies had sweet eliciting smiles, lip smacking, and sour eliciting protrusion of tongue These reactions make good evolutionary sense Animals tend to be neophobic, and human children are reluctant to try new things One experiment asked a group of subjects to taste two groups of food (that were the same). When the items were accurately named (chopped tomatoes, oatmeal, beefsteak) more willing them when given novel names (pendula fruit, lat, langua steak) Taste Moisture is necessary for taste buds to function. Taste buds are located in the fungiform papillae or bumps on the tongue. There are many taste buds in each bump. Supertasters have an extraordinary number of taste buds and fungiform papillae. They can always taste PROP. Spicy food tastes very hot to supertasters as the taste bud are linked to pain receptors that respond to the hot oil. Taste Sensory interaction- taste is highly dependent on smell. The two together create flavor. This is evident when you have a cold. Taste also depends on sight. If it doesn’t look good, it doesn’t taste good. Chocolate increases serotonin particularly in women and increases happiness. Smell Olfactory nerve Olfactory bulb Nasal passage Receptor cells in olfactory membrane Smell Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste, there are many different forms of smell. Age, Sex and Sense of Smell Number of correct answers Women and young adults have best sense of smell 4 Women 3 Men 2 0 10-19 20-29 30-39 40-49 50-59 60-69 Age Group 70-79 80-89 90-99 Smell Theories of smell: Lock and Key- odor molecules fit specific receptor sites Receptor construction- as a molecule enters the system an appropriate receptor is formed. Smell Olfactory cells are located on the cilia in the upper portion of the nose. They are surrounded by mucus to trap odor molecules. Smell is associated with memory encoding. Smell declines with age Anosmia- 2 million people have no sense of smell. Can be the result of head trauma or infection or cold. Smell Pheromones-sexual signals through smell. Used by animals and maybe humans. Ex. Sweaty t-shirts, menstrual synchrony Smell is important to taste. Ex. When one has a cold.