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Transcript
Unit 4: SENSATION AND PERCEPTION List the five senses below 1. 2. 3. 4. 5. Sensation and Perception: The Basics Sensation: Raw information that comes from the senses What is this? Sensation and Perception: The Basics Perception: The process through which people take raw sensations from the environment and give them meaning, using knowledge, experience, and understanding of the world. Perception = Sensation + Meaning Sensation and Perception: The Basics Bottom-Up Processing Informational Processing that analyzes the raw stimuli entering through the many sensory systems and works up the brain Top-Down Processing Information Processing that draws on expectations and experiences to interpret incoming sensory information. It is guided by higher-level mental processes Sensing the World: Some Basic Principles Psychophysics: the study of relationships between the physical characteristics of stimuli, (such as their intensity), and our psychological experience of them Sensing the World: Some Basic Principles Absolute Threshold: The weakest amount of stimulation needed to detect a stimulus 50% of the time Sensing the World: Some Basic Principles Examples of Absolute Thresholds Vision: A candle flame viewed from a distance of about 30 miles on a dark night Hearing: The ticking of a watch from about 20 feet away in a quiet room Smell: About one drop of perfume diffused throughout a small house Taste: About 1 teaspoon of sugar dissolved in 2 gallons of water Touch: The wing of a fly falling on a cheek from a distance of about .4 inch (1 centimeter) Sensing the World: Some Basic Principles Absolute Threshold are different for people due to psychological and biological factors. What are some examples? Sensing the World: Some Basic Principles Signal-Detection Theory: A theory that predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). This theory assumes there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and level of fatigue. 1.) Sensation and Perception: The Basics Our ability to distinguish between sensory stimuli takes into account: Our motivation Our expectations Our learning Our physical fatigue The signal detection theory says that distinguishing sensory stimuli takes into account not only the strength of the stimuli but also such elements as setting, ones’ physical state, mood, attitude, etc. Provide an example of something that could raise or lower your absolute threshold Would your example raise or lower your absolute threshold? (Circle raise or lower) Example: I am on a diet and someone in the theatre (3 rows ahead of me) is eating popcorn. I can smell the popcorn. Being on a diet lowers my absolute threshold for smell Sensing the World: Some Basic Principles Subliminal Stimulation Subliminal: below threshold stimuli Can we detect subliminal stimuli? Can subliminal messages manipulate our behavior? http://jeffmilner.com/backmasking/another-one-bites-the-dust-backwards.htm Sensing the World: Some Basic Principles Priming: the activation, often unconsciously, or certain associations, thus predisposing one’s perception, memory, or response Sensing the World: Some Basic Principles Difference Threshold (A.K.A.: JND): The minimum amount of difference needed to detect a change in stimulus 50% of the time Can you detect the difference in color between these two hues? 1.) Sensation and Perception: The Basics People’s difference thresholds vary slightly What jobs would require a person to have a small difference threshold? Sensing the World: Some Basic Principles Weber’s Law: Sensory thresholds for detecting differences (JND) are a roughly constant proportion of the size of the original stimulus Difference thresholds grow with the magnitude of the stimulus Sensing the World: Some Basic Principles As we get older, our JND increases Sensing the World: Some Basic Principles Fechner’s Law Constant increases in physical energy will produce smaller increases in perceived magnitude Sensing the World: Some Basic Principles Sensory Adaptation: our diminishing sensitivity to an unchanging stimulus Why does sensory adaptation occur? Sensing the World: Some Basic Principles Sensory Adaptation Why does sensory adaptation occur? Sensory adaptation allows us to detect potentially important changes in our surroundings while ignoring unchanging aspects of them. Example? Sensing the World: Some Basic Principles We will never completely adapt to extremely intense sensations such as severe pain or freezing cold. This is adaptive because to ignore such stimuli might be harmful or even fatal. Vision Transduction: conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret Example: the ear receives sound energy and transduces it into neural activity that people recognize as voices Vision Vision depends on the interaction of the eye and the brain. The eyes sense objects and convey this information to the brain, where visual perception takes place. Vision Stimulus Energy: Light Energy Light is described in wavelengths Can we see all wavelengths of light? No Vision The Stimulus Input: Light Energy Wavelength: the distance from one wave peak to the next. Wavelength determines hue/color Vision Light The colors of the visible spectrum from longest to shortest wavelengths are: Red Orange The mnemonic device to remember this is: Yellow ROY G. BIV Green Blue Indigo Violet Vision The Stimulus Input: Light Energy Amplitude: the height of a wave from peak to trough. It determines the intensity (or brightness of color) The Eye The Eye The eye works much like a camera does The Eye Parts of the Eye The Eye Cornea: Covers and protects the eye. It is through this structure that the light first enters the eye The Eye Parts of the eye Pupil: An opening in the eye just behind the cornea, through which light passes. The size of this opening can be affected by the amount of light present and by emotions 2.) Vision Parts of the Eye Iris: The part of the eye that gives its color and adjusts the amount of light entering it The Eye Parts of the eye Lens: The transparent structure behind the pupil that focuses light onto the retina The Eye Parts of the Eye Retina: The surface at the back of the eye onto which the lens focuses light rays The retinal image is upside-down and reversed Cool People Like Raduege Cornea Pupil Lens Retina The Eye The Blind Spot: The point at which the optic nerve leaves the eye creating “blind” spot because no receptor cells are located there The Eye Accommodation: The process by which the eye’s lens changes shape to focus near or far objects on the retina The Eye Visual Acuity: the sharpness of vision Visual Acuity is determined by the ability to see visual details in normal light. Visual Chart Acuity is measure by a Snellen The Eye Visual Acuity Nearsighted: when you have to be close to an object to make out its details (you can see close but not far). Farsighted: when you have to be far away from an object to make out its details (you can see far but you can’t see close) The Eye Normal Vision Nearsighted When the image reaches the retina, the rays are spreading out, blurring the image. Farsighted Light rays from nearby objects come into focus behind the retina, resulting in blurred images The Retina Rods and Cones Rods: Retinal receptors that detect black, white, and gray; they are necessary for peripheral and twilight vision, when cones don’t respond. They are located around the peripheral of the retina The Retina Cones: Receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations. They are concentrated at the center of the retina (fovea) The Retina The Retina Optic Nerve The nerve that carries neural impulses from the eye to the brain Visual Information Processing Feature Detection We process information at progressively more abstract levels. The information from the retina’s 130 million rods and cones is received and transmitted by the million or so ganglion cells whose axons make up the optic nerve. When individual ganglion cells register information in their region of the visual field, they send signals to the visual cortex. Visual Information Processing Features Detectors Nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement Parallel Processing Parallel Processing: The processing of several aspects of a problem simultaneously (color, shape, motion, and depth); the brain’s natural mode of information processing for many functions, including vision (simplistically put…doing several things at once) Parallel Processing Blind sight: The capacity of some individuals with blindness in parts or all of the visual field to detect and localize visual stimuli presented within the blind field region. However, these visual capacities are not accompanied by awareness. They have been demonstrated only in experimental conditions, when participants are forced to guess. Blind sight therefore does not help individuals to compensate for their loss of vision Color Vision Young-Helmholtz Trichromatic Theory Any color can be created by combining light waves of the three primary colors which are red, green, and blue Color Vision Young-Helmholtz Trichromatic Theory The human eye has three types of receptors (cones) each of which is most sensitive to one of the primary colors. When combined in differing amounts, they can produce the perception of any color www.exploratorium.edu/exhibits/f_exhibits.html Color Vision Short wavelength cones Respond most to blue Medium wavelength cones Are most sensitive to green Long wavelength cones Respond best to red Color Vision Opponent-Process Theory: This theory states that opposing retinal processes enable color vision. These opposing processes are: Red-green Santa Claus Yellow-blue at a Marquette game White-black reading a newspaper Color Vision Opponent-Process Theory: There are three different kinds of color processing neural mechanisms in the visual system. These neurons work on an “on-off’ system If the red-green mechanisms is activated by light in the red wavelengths it will be shut down by lights in the green range. Others are turned on by green and off by red. So if you detect red at a particular point in the retina, you cannot simultaneously detect the opposing color (green) at the same point; you therefore cannot see a greenish red Color Vision Opponent-Process Theory: If both members of a pair are stimulated equally, they cancel each other out and this leaves only gray. Member from non-opponent pairs may interact and be stimulated at the same time result in colors such as yellow-red or blue green The black-white system respond to differences in brightness levels Color Vision Support for the opponent-process theory Complementary colors: You can’t mix yellow/blue or red/green to get intermediate colors, simultaneous presentation of both colors typically produce white or gray tones because they are complementary colors. The opponentprocess theory explains this by saying that you cannot signal red and green at the same time. In contrast, you get orange when the red and yellow neural mechanisms are simultaneously stimulated Color Vision Support for the opponent-process theory Color after image: If you stare at a color for a long time you will see a visual image that persists after it is removed; the color of the afterimage is the complement. Why? If you stare at something green for a long time you fatigue the green receptors. Then when you state at something white (which contains all colors) the green receptors, which are fatigued, do not fire, only the red receptors fire normally www.exploratorium.edu/exhibits/f_exhibits.htm Color Vision Support for the opponent-process theory Color Blindness: In partially color blind people they usually have trouble with red/green or yellow/blue which are opponent pairs Color Vision Color Blindness: People who do not have normal color vision are said to be color blind Normal Vision Color Blind Vision Color Vision Color Blindness People who are totally color blind (this is rare) see only black and white A more common type is red-green color blindness where people have a difficult time seeing shades of red and green Color Vision Color Blindness More men than woman are color blind because it is a trait carried on the X chromosome Color Vision Which theory of color vision is correct? They both are. Both theories are needed to account for the complexity of visual sensations of color Color Vision Color Vision = + = Trichromatic Theory + Opponent Process Theory Color Vision There are two steps in color processing 1. 2. The cones in the retina respond to and encode color in terms of red, green, and blue. This supports the Trichromatic Theory, which describes the visual processing in the retina The ganglion cells respond to and encode color in terms of opposing pairs en route to the visual cortex. This supports the OpponentProcess Theory, which describes color vision at higher levels within the brain Path of Light as it enters the eye Cool People Like Raduege Big Geeks Oh No Totally, Oh Lord Color Constancy Color Constancy: Perceiving familiar objects as having consistent color, even if changing illumination alters the wave-length reflected by the object. If it weren’t for perceptual constancy the world would seem ever-changing and chaotic. Hearing Audition The sense of hearing Hearing The stimulus for hearing is sound waves. These sounds waves move in roughly the same fashion as do light waves, however they have a much slower range of speed Hearing Amplitude The height of a sound wave Amplitude determines how loud a sound is Hearing Loudness: Measured in units called decibels (dB) Determined by the height (amplitude) of the sound wave. The higher the amplitude of the wave, the louder the sound When sounds reach a decibel level beyond 130Db, they can become painful Continued noise at upper limits (85dB) can cause permanent hearing loss Hearing Hearing Frequency the complete wavelengths that pass by a given point each second Hearing Frequency Frequency is measured in Hertz units (Hz)= number of cycles per second Wavelengh and frequency are related. The longer the wavelength, the lower the frequency, and vice versa Hearing Frequency and Pitch Frequency determines pitch High frequency/short wavelength= high pitch Examples? Low frequency/long wavelength=low pitch Examples? We hear sound best that have the frequencies within the range of the human voice Hearing “Oh Grandma, what big ears you have.” “The better to hear you with my dear.” True or false? Hearing Parts of the Ear Pinna: the ear flap Hearing Auditory Ear Canal The hollow tube that conducts sound through the external ear, from the pinna to the ear drum Hearing Ear Drum: The Ear Drum is a piece of skin stretched over the entrance to the ear, it separates the external ear from the middle ear and serves to transform the pressure waves of sounds into mechanical vibrations of the bone of the middle ear. Hearing Middle Ear (Hammer, Anvil, Stirrup) The hammer, anvil and stirrup are the auditory ossicles that transmit sound vibrations from the tympanic membrane to the oval window of the inner ear. The ossicles allow efficient transmission of sound from air to the fluid-filled cochlea Hearing Middle Ear (Malleus, Incus, Stapes) hammer anvil stirrup Hearing Oval Window: The membrane in the wall of the cochlea to which the stapes is attached. By the time the sound has reached the oval window, it is many times stronger than when it first struck the eardrum. Oval Window Hearing Semicircular Canals Semicircular Canals A set of three looped tubular channels in the inner ear that detect movements of the head and provide the sense of equilibrium that is essential for maintaining balance. They are oriented roughly at right angles to each other, and can therefore monitor movements in each of three different planes. Hearing Cochlea Cochlea is the Greek word for “snail”. It is filled with fluid and small hairs that vibrate to incoming sounds. These vibrations generate neural impulses that are transmitted to the brain Hearing Basilar Membrane: the floor of the fluid filled duct that runs through the cochlea. This organ contains the hair cells called cilia. The movement of the fluid within the cochlea causes the cilia to bend and as they bend, nerve impulses are sent via the auditory nerve to the brain Hearing Auditory Nerve The Auditory Nerve is a bundle of nerves that carry stimuli from the hair cells of the cochlea to the temporal lobe of the brain where auditory processing occurs Three Sections of the Ear OUTER EAR MIDDLE EAR INNER EAR ___________the sound. Sound travels by means of ___________the sound by means of ___________ sound into neural energy by means of Consists of: Consists of: Consists of: Hearing How do we perceive pitch? Place Theory: This theory links the pitch we hear with the place where the cochlea’s membrane is stimulated. Hearing How do we perceive pitch? Place Theory High Frequency waves (high pitched sounds) trigger activity mostly near the beginning/base of the cochlea’s membrane, near the oval window Hearing How do we perceive pitch? Place Theory Middle Frequency waves (medium pitched sounds) trigger activity at the apex of the cochlea Hearing How do we perceive pitch? Place Theory The place theory describes how we hear high frequency/high pitched sounds but doesn’t do a great job of explaining how we hear low pitched sounds Hearing Frequency Theory: This 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 The frequency theory describes best how we hear low frequency/low pitched sounds Hearing Locating Sound The placement of our ears allows us to enjoy stereophonic hearing (three-dimensional) If a sound is louder in our right ear and reaches it before it reaches our left ear, we perceive the sound as coming from the right Hearing Locating Sound: It is difficult to locate sounds that are directly in front, behind, or on top of our ears. Why? Because the sound reaches both of our ears at the same time and with the same intensity. Hearing Deafness About 2 million Americans are deaf There are two basic types of deafness Conductive deafness Sensorineural deafness (nerve deafness) Hearing Conductive Deafness Occurs due to damage to the middle ear (damage to the mechanical system that conducts sound waves to the cochlea) Since it is caused by the ear’s inability to conduct vibrations it can be helped by a hearing aid which will amplify the vibrations Hearing Sensorineural Deafness (Nerve Deafness) Occurs due to damage to the inner ear (the cochlea’s receptor cells or to the auditory nerves) Could result from: Disease Prolonged Exposure to very loud sounds Biological changes associated with age Hearing Because it is due to damage to the inner ear, a hearing aid will not be very helpful. However, today cochlear implants are being used to help people with this type of deafness Hearing Cochlear Implant: A device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea (The first implant was done in 1980) Hearing Controversy: One group supports the use of cochlear implants to medically "repair" deafness in children with a sensorineural hearing loss while the other believes the children's natural condition should be emphasized. Those who support cochlear implants believe that normalization is the key to success for deaf children. On the other side, the Deaf community and others opposed to cochlear implants feel that deafness should be looked at as a cultural identity, not a disability Hearing Cochlear Implants Sensory Compensation Some also argue that sensory compensation, which enhances other senses, gives deaf people an advantage that the hearing do not have Other Important Senses Touch: our sense of touch is a mix of at least four distinct skin senses pressure warmth cold pain These four senses combine to produce other sensations, such as “hot” Other Important Senses Touch The sense of touch codes information about two aspects of an object in contact with our skin Intensity: how heavy it is (coded by the firing rate of neurons. The higher the rate of firing, the heavier the objects) Location: where the touch is Other Important Senses Pain: There is not one type of stimulus that triggers pain, and there are no special receptors for pain. However, pain is an alarm system that draws our attention to some physical problem. Other Important Senses Pain There are two types of nerve fibers that carry pain signals from the skin to the spinal cord A-delta fibers: carry sharp, pricking pain sensations. They are myelinated C fibers: carry chronic, dull aches and burning sensations Other Important Senses Biological, Psychological, and Social- Cultural Influences on Pain The biopsychological approach views pain not only as product of biological influences but also as a result of psychological influences such as the situation and our past experience and social influences such as cultural expectations and the presence of observers Other Important Senses Gate-Control Theory: This theory states that there is a “gate” in the spinal cord that either lets pain impulses travel upward to the brain or blocks their progress. The major parts of this theory are incorrect. However, there is some evidence that natural mechanisms can block pain sensation by coming in to the spinal cord at the same time as the pain gets there and “taking over” the pathways that the pain impulses would have used. Other Important Senses Pain Control Pain is controlled through a combination of medical and psychological treatments. Other Important Senses Taste: the sense of taste is called gustation Taste (a chemical sense) is composed of Sweet Sour Salty Bitter Umami (meat, fish, some vegetables, and cheeses) And aromas that interact with information from taste buds Other Important Senses This theory has largely been debunked Babies seem to be born disliking bitter tastes Other Important Senses These taste buds on the top and sides of the tongue and in the back and roof of the mouth contain taste receptor cells. These cells send information to an area of the temporal lobe near the area where olfactory information is received. Taste receptors replace themselves every week Other Important Senses Supertasters: (25%) Have more papillae than the average person Other Important Senses Sensory Interaction: We taste with more than just our taste buds. Our sense of smell and vision are also involved in our sense of taste. Other facts about taste Food deprivation or salt deficiency makes sweet or salty foods taste better Flavor is affected by tactile properties Warm food= sweeter Other Important Senses Smell: The sense of smell is called olfaction Olfactory receptors (located in the nasal cavity) are involved in smell The physical stimulus for smell is chemical substances Name of sense Seeing Hearing Tasting Touching Smelling Stimulus Location of receptors Other Important Senses Facts about Smell The ability to identify scents peaks in adulthood and gradually declines thereafter. The sense of smell shows sensory adaptation. The perceived strength of an odor usually declines to less than half of its original strength within 4 minutes Other Important Senses There is a strong relationship between olfaction and emotional memory. An odor’s ability to spontaneously evoke memories is due, in part, to the close connections between brain areas that process smell and those involved in memory storage Other Important Senses Kinesthesia: The system for sensing the position and movement of individual body parts. Sensors in the muscles, tendons, and joints are continually providing our brain with information Other Important Senses Vestibular Sense: Monitors the head’s (and thus the body’s) position and movement. The receptors for the vestibular senses are located in the semi-circular canals (thee small fluid-filled canals located in the inner ear) and the vestibular sacs located in the inner ear