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Myers’ PSYCHOLOGY (8th Ed) Chapter 5 Sensation AP Psychology 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 Bottom-Up Processing analysis that begins with the sense receptors and works up to the brain’s integration of sensory information Top-Down Processing information processing guided by higherlevel mental processes as when we construct perceptions drawing on our experience and expectations 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 usually defined as the stimulus needed for detection 50% of the time Difference Threshold minimum difference between two stimuli that a subject can detect 50% of the time just noticeable difference (JND) increases with magnitude 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 75 50 Subliminal stimuli 25 0 Low Absolute threshold Intensity of stimulus Medium When stimuli are detectable less than 50% of the time (below one’s absolute threshold) they are “subliminal”. Sensation- Thresholds Weber’s Law- to perceive a difference between two stimuli, they must differ by a constant proportion light intensity- 8% weight- 2% tone frequency- 0.3% Sensory adaptation- diminished sensitivity with constant stimulation Vision- Stabilized Images on the Retina Vision Transduction- conversion of one form of energy to another Wavelength- the distance from the peak of one wave to the peak of the next Hue- dimension of color determined by wavelength of light Intensity- amount of energy in a wave determined by amplitude brightness loudness Vision- 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) Vision Pupil- adjustable opening in the center of the eye Iris- a ring of muscle the 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 Vision Vision Accommodation change in shape of lens focus near objects Retina inner surface of eye light sensitive contains rods and cones layers of neurons beginning of visual information processing Vision Acuity- the sharpness of vision Nearsightedness nearby objects seen more clearly lens focuses image of distant objects in front of retina Farsightedness faraway objects seen more clearly lens focuses near objects behind retina Vision Normal Vision Nearsighted Vision Farsighted Vision Retina’s Reaction to Light- Receptors Cones near center of retina (fovea) fine detail and color vision daylight or well-lit conditions Rods peripheral retina detect black, white and gray twilight or low light 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 Vision- Receptors Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No Pathways from the Eyes to the Visual Cortex Visual Information Processing Feature Detectors neurons in the visual cortex respond to specific features shape angle movement Cell’s responses Stimulus How the Brain Perceives Illusory Contours Visual Information Processing Parallel Processing simultaneous processing of several dimensions through multiple pathways color motion form depth Visual Information Processing Abstraction: Brain’s higher-level cells respond to combined information from feature-detector cells Feature detection: Brain’s detector cells respond to elementary features-bars, edges, or gradients of light Retinal processing: Receptor rods and conesbipolar cells ganglion cells Recognition: Brain matches the constructed image with stored images Scene Visual Information Processing Trichromatic (three color) Theory Young and Helmholtz three different retinal color receptors red green blue Color-Deficient Vision People who suffer red-green blindness have trouble perceiving the number within the design 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 Opponent ProcessAfterimage Effect Audition Audition the sense of hearing Frequency the number of complete wavelengths that pass a point in a given time Pitch a tone’s highness or lowness depends on frequency The Intensity of Some Common Sounds Audition- The Ear Outer Ear Auditory Canal Eardrum Middle Ear hammer anvil stirrup Inner Ear oval window cochlea basilar membrane hair cells 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 Audition 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 Audition Older people tend to hear low frequencies well but suffer hearing los 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 Touch Skin Sensations pressure only skin sensation with identifiable receptors warmth cold pain 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 Taste Taste Sensations- biological wisdom, 200 sweet sour salty bitter UMAMI Sensory Interaction one sense may influence another as when the smell of food influences its taste Synaesthesia- one sense triggers another??? Smell Illustration p. 231 Olfactory nerve Olfactory bulb Nasal passage Receptor cells in olfactory membrane Smells evoke memories! 20,000 breaths a day, OLFACTION Just like taste, smell is a chemical sense. 5 million receptor cells at the top of each nostril. Babies recognize Mom’s scent! We can detect smell but it is hard to describe them. Easier to explain sounds. We have our own chemical smell signature except for identical twins… 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 Body Position and th Movement- the real 6 Sense Kinesthesis- 200 muscles for 1 step! the system for sensing the position and movement of individual body parts Vestibular Sense the sense of body movement and positionbiological gyroscope. including the sense of balance- inner ear, semicircular canals- vestibular sacs, cochlea, cerebellum- helps you maintain balance.
