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Chapter 6 Part I: Introductory Ideas & Terms Quiz Questions-9 Nov 1. The purpose of the pupil is to a. b. c. d. e. Focus light on the retina Process color. Allow light into the eye. Enable night vision Detect specific shapes 2. Cells that respond to specific edges, lines, angles and movements are called a. b. c. d. e. Rods. Cones. Ganglion cells. Feature detectors Bipolar cells. Nov 9 1. The purpose of the pupil is to a. b. c. d. e. Focus light on the retina Process color. Allow light into the eye. Enable night vision Detect specific shapes 2. Cells that respond to specific edges, lines, angles and movements are called a. b. c. d. e. Rods. Cones. Ganglion cells. Feature detectors. Bipolar cells. Sensation & Perception To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. When we select, organize, and interpret our sensations, the process is called perception. “Perception creates an interpretation of sensation.” Illusions… Bottom-up Processing (Sensation) 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.” Top-Down Processing (Perception) Circle Test Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT Aocincdrg to rsecaerh at Cmdiagbre Uinservtiy, it desno’t mtetar in waht oredr the lteters in a wrod are, the olny ipranmoett tinhg is taht the fsrit and lsat lteetr be at the rghit pclae. The rset can be a ttaol mses and you can siltl raed it whotuit a pbeolrm. Tihs is bcuseae the haumn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Psychophysics Established by Gustav Fechner in 1860 it is the study of the relationship between physical characteristics of stimuli and our psychological experience with them. Physical World Psychological World Light Brightness Sound Volume Pressure Weight Sugar Sweet Absolute Threshold The minimum stimulation needed to detect a particular stimulus 50% of the time. Absolute Threshold Absolute Threshold Intensity No No Yes Yes Yes Observer’s Response Detected Tell when you (the observer) detect the light. Signal Detection Theory Signal Detection Theory predicts how and when we detect the presence of a faint stimulus/signal in the midst of background stimulation/”noise” According to this theory, there is no single absolute threshold and experiences, expectation, motivation and tiredness play a role in stimulus detection. Difference Threshold Difference Threshold (also called just noticeable difference or JND) is the minimum difference between two stimuli required for detection 50% of the time, Difference Threshold No No Yes Observer’s Response Tell when you (observer) detect a difference in the light. Subliminal Threshold http://yeli.us/Flash/Fire.html Subliminal Threshold occurs when stimuli are below one’s absolute threshold for conscious awareness. “Hungry? Eat Popcorn” (1/3000 of a second for 18% increase!) James Vicary’s 1957 Picnic study in New Jersey was a hoax Weber’s Lawquarter test Ernst Weber noted that two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Stimulus Constant (k) Light 8% Weight 2% Tone 3% $1.00 → $1.01 $1.00 → $1.10 Sensory Adaptation salt water test fruit marker test Diminished sensitivity is a consequence of constant stimulation. If you just enter a room, you will smell its natural odor, but after a while you won’t notice the smell Your body “gets used” to the temperature of the water After a while you do not notice the band-aid on your arm • What good does sensory adaptation do for us? - It allows us to “filter out” stuff that doesn’t change and immediately recognize changes in our environment. Part II: Transduction (Sight, Hearing, Touch, Taste & Smell) Transduction = In sensation, the transformation of stimulus energy into neural impulses. Phototransduction is the conversion of light energy into neural impulses that the brain can understand. The Stimulus Input: Light Energy Visible Spectrum Wavelength (Hue) Hue (color) is the dimension of color determined by the wavelength of the light. Wavelength is the distance from the peak of one wave to the peak of the next. Wavelength (Hue) Violet Indigo 400 nm Short wavelengths & High frequency Blue Green Yellow Orange Red 700 nm Long wavelengths & Low frequency Different wavelengths of light result in different colors. Intensity (Brightness) Intensity is the amount of energy in a wave determined by the amplitude (height). It is related to perceived brightness. Intensity (Brightness) Blue color with varying levels of intensity. As intensity increases or decreases, blue color looks more “washed out” or “darkened.” The Eye 1. 2. 3. 4. Cornea: Transparent tissue where light enters the eye. Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light. Lens: Focuses the light rays on the retina. Retina: Contains sensory receptors that process visual information and sends it to the brain. Retinal arteries/veins Fovea Aqueous humor Ciliary muscle The Lens Lens is the transparent structure behind the pupil that changes shape to focus images on the retina. Accommodation is the process by which the eye’s lens changes shape to help focus near or far objects on the retina. Problems with Visual Acuity Nearsightedness: A condition in which nearby objects are seen more clearly than distant objects. Farsightedness: A condition in which faraway objects are seen more clearly than near objects. The Retina: orange paper test. eye movement test Retina: The lightsensitive inner surface of the eye, containing receptor rods (black/white) and cones (color) in addition to layers of other neurons (bipolar, ganglion cells) that process visual information. Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which form the optic nerve. Photoreceptors Optic Nerve, Blind Spot & Fovea Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. This creates a blind spot. Fovea: Central point in the retina around which the eye’s cones cluster. Visual Information Processing Feature detectors: nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle or movement “You look with your eye, but see with the brain” Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex. David Hubel & Torsten Wiesel won the Nobel Prize in Medicine in 1981 Parallel Processing Processing of several aspects of the stimulus simultaneously is called parallel processing. The brain divides a visual scene into subdivisions such as color, depth, form and movement etc. Theories of Color Vision Young-Helmholtz Trichromatic (three-color theory): Based on behavioral experiments, Helmholtz suggested that the retina should contain three receptors that are sensitive to red, blue and green colors. Problem With the Trichromatic Theory? • How can colorblind people who cannot see red and green, still see yellow (which according to the Trichromatic Theory is a mix of red and green light)? Color Blindness- test Genetic disorder (more males) in which people are blind to green or red colors. This supports the Trichromatic theory. Ishihara Test Opponent Process Theory • Hering proposed that we process four primary colors combined in pairs of red-green, blue-yellow, and blackwhite. • The retina and thalamus have neurons that are turned “on” by one of the colors of the pair but turned “off” by the opposite color • Dual-Process Theory combines the Trichromatic Theory with the Opponent Process Theory Afterimages can be created by the Opponent Process Theory Additive Color Mixing If three primary colors (lights) are mixed, the wavelengths are added and the color white is the result. Subtractive color mixing= mixing three primary colors (pigments) subtracts wavelengths (fewer wavelengths are reflected back) and the color black is the result. Color Constancy optical illusion video Color of an object remains the same under different illuminations. However, when context changes the color of an object may look different. Acoustical Transduction “You have to have an ear to produce a sound” Conversion of sound waves into neural impulses in the hair cells of the inner ear. Sound waves are composed of compression of air molecules. Frequency (Pitch) sounds kids can hear, adults cannot Frequency (pitch): The dimension of frequency determined by the wavelength of sound. Wavelength: The distance from the peak of one wave to the peak of the next. Intensity (Loudness) Intensity (Loudness): Amount of energy in a wave, determined by the amplitude, relates to the perceived loudness. Loudness of Sound 120dB 70dB Quality (Timbre) Quality (Timbre): Characteristics of sound from a zither and a guitar allows the ear to distinguish between the two. Zither Guitar The Ear- video on hearing Outer Ear: The Pinna collects sounds. Middle Ear: Chamber between eardrum and cochlea containing three tiny bones (ossicles: hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window. Inner Ear: Innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs. Pinna aka Ossicles (Hammer, Anvil & Stirrup) Cochlea Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals. Theories of Audition Place Theory suggests that sound frequencies stimulate the basilar membrane at specific places resulting in perceived pitch. Also theorized by Helmholtz Explains how we hear high pitched sounds well but doesn’t explain how we hear low pitched ones very well Theories of Audition Frequency Theory states that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. Sound Frequency 100 Hz 200 Auditory Nerve Action Potentials Theories of Audition • The problem with the Frequency Theory is that neurons cannot fire faster than 1000 times per second • So again, there must be a combination of theories (i.e. Place and Frequency Theory principles work together somehow) Localization of Sounds hand clapping activity; boy who sees video Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound. 1. Intensity differences 2. Time differences Time differences as small as 1/100,000 of a second can cause us to localize sound. The head acts as a “shadow” or partial sound barrier. Hearing Loss Conduction Hearing Loss: Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea. Examples: damage to eardrum or hammer/anvil/stirrup (vibration is affected) Sensorineural Hearing Loss: Hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve, also called nerve deafness. - most people born deaf suffer this type of loss Cochlear implants are electronic devices that enable the brain to hear sounds. Hearing Deficits Older people tend to hear low frequencies well but suffer hearing loss when listening for high frequencies. Body Position & Movement The sense of our body parts’ position and movement is called kinesthesis. The vestibular sense monitors the head (and body’s) position and helps with maintaining balance. Vestibular sense is governed by fluid filled sacs in semicircular canals of the inner ear. Whirling Dervishes Wire Walk Touch (a.k.a. Tactile Senses) The sense of touch is a mix of four distinct skin senses—pressure, warmth, cold, and pain. Skin SensesOnly 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. Ashley Blocker suffers from Congenital Analgia. She feels neither pain nor extreme hot or cold. Biopsychosocial Influences Gate-Control Theory Proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed. Pain can be controlled by a number of therapies including, drugs, surgery, acupuncture, exercise, hypnosis, and even thought distraction. Smell (a.k.a. Olfactory Sense) 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, Gender, and Smell Ability to identify usually smell peaks during early adulthood, but steadily declines after that. Women are better at detecting odors than men. Smell & Memories The brain region for smell (in red) is closely connected with the brain regions involved with memory (limbic system). That is why strong memories are made through the sense of smell. Taste (a.k.a. Gustatory Sense) 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 (savory/meaty) http://www.pbs.org/wgbh/nova/sciencenow/0404/01.html Sensory Interaction When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor.