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Module 09 Sensation Let’s see if you labeled correctly: Let’s take in our surroundings: • What do you see? – What shapes are around you? What colors? • What sounds are you listening to? • What can you feel? – Is your clothing comfortable, what about your chair? • What do you taste? • Are there any odors? • This awareness of the world around you is called sensation. Sensation • The process by which our sensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli from the environment • Bottom-up processing: – Information processing that focuses on the raw material entering through the eyes, ears, and other organs of sensation Perception • The process of organizing and interpreting sensory information • Top-Down Processing: – Information processing that focuses on expectations and experiences in interpreting incoming sensory information Sensation and Perception • Do you see some marks that look the same as others, but are meant to be interpreted differently? – Sensation brings image from paper to your brain, a bottom-up process of gathering environmental info through the senses. – Perception involves knowing what to make of the individual marks in the sentence. This top-down interpretation relies on your experiences with, and expectations about, language. Thresholds: an edge or a boundary What are absolute thresholds and difference thresholds, and how do they differ? Absolute & Difference Threshold • Absolute threshold: – The minimum stimulation needed to detect a particular stimulus. – Dimmest star in the sky would be right at the absolute threshold for vision. – What about for taste/hearing? • Difference threshold – Aka: just noticeable difference – Minimum difference that a person can detect b/t 2 stimuli. – The smallest detectable change in a stimulus. • When does sound become too loud or when is something too tight? Signal Detection Theory: What is it, and why is it a significant accomplishment for modern psych? • What’s that on the x-ray: scar tissue or a tumor??? • Grew out of the Cold War. – To improve our ability to detect incoming nuclear warheads in time to respond appropriately. • National security depends on accurate signal detection! • Set of formulas and principles that predict when we will detect the presence of a faint stimulus (signal) amid background stimulation (noise) – Detection depends on qualities of the stimulus, the environment, and the person who is detecting. Signal Detection Theory (cont.) • 3 Kinds of variables: – 1. Stimulus • How bright is the blip on the radar screen? – 2. Environmental • How much distracting noise is there in the room with the radar equipment? – 3. Organismic • Is the operator properly trained and motivated? • Now used in ways other than militaristic: – Air traffic control, make sure one plane isn’t too close to another, accurately detecting tumors, etc. Sensory Adaptation How does sensory adaptation make your life easier? • When we filter out the non-changing aspects of our environment. – If a stimulus is constant and unchanging, eventually a person may fail to respond to it. – Diminished sensitivity as a result of constant stimulation. – EX: getting into a swimming pool that seems rather chilly • What happens at first? After a while? – EX: ever look for your sunglasses and realize they are on your head? Selective Attention How does selective attention relate to effective study skills? • Focusing conscious awareness on a particular stimulus to the exclusion of others – You can’t pay attention to every single little thing at once! • The ability to focus on one stimulus at a time – Ever blocked out sound to help you study/sleep? • Allows a person to function in a world filled with many stimuli So… what do you see? • You can attend to one view or the other: – Old or young woman • You can earn learn to switch back and forth. • You cannot see both images at once. Module 9: Sensation The Visual System: The Nature of Light What is light? Electromagnetic Energy • Light enters the eye as waves of electromagnetic energy. • An energy spectrum that includes Xrays, radar, and radio waves . – A small portion of the spectrum includes light visible to the human eye The Electromagnetic Spectrum • Light is a form of electromagnetic energy. This energy travels in waves, ranging from short gamma rays to long radio waves. The human eye can detect only a small portion of these waves, the visible spectrum, as light. 1st characteristic of waves: Hue • The color of light as determined by the wavelength of the light energy – What color is this power point slide? • Includes: red, orange, yellow, green, blue, indigo and violet (ROY G BIV) • The eye can detect 7 million separate hues Wavelength 2nd characteristic of waves: Amplitude • The brightness of light as determined by height of the wave • The taller the wave, the brighter the color – Thus greater amplitude stronger hue. Module 9: Sensation The Visual System: The Structure of the Visual System What are the major parts of the visual system, and what roles do these parts play in our ability to see? • Light first strikes the cornea! • The clear bulge on the front of the eyeball • Begins to focus the light by bending it toward a central focal point • Protects the eye Cornea • Colored part • A ring of muscle tissue that forms the colored portion of the eye; creates a hole in the center of the iris (pupil) • Regulates the size of the pupil by changing its size--allowing more or less light to enter the eye Iris Pupil • The adjustable opening in the center of the eye that controls the amount of light entering the eye (surrounded by the iris) – In bright conditions the iris expands, making the pupil smaller. – In dark conditions the iris contracts, making the pupil larger. • Ex: wake up in middle of night go to the bathroom, turn on light and watch your pupil shrink in the mirror. – Restricting light b/c it’s too bright for you. Lens • A transparent structure behind the pupil; focuses the image on the back of the eye (retina) • Muscles that change the thickness of the lens change how the light is bent thereby focusing the image • Lens not letting you focus? – Get contacts/glasses Nearsightedness & Farsightedness • With normal vision, the lens changes in thickness to cause the light rays from a viewed object to converge at the retina. – The result is a clear focused image. • In a nearsighted person’s eye, the lens causes light rays from distant objects to converge in front of the retina, which blurs the image. • If a person is farsighted, the lends causes light rays from close objects to converge behind the retina. • Corrective lenses, help the eye’s own lens focus the image correctly. Retina • All other structures • Made up of three (cornea, pupil, iris, layers of cells lens) direct traffic – – Receptor cells move visual info to retina! – Bipolar cells • Important processing – Ganglion cells center at the back of the eyeball • Light-sensitive surface with cells that convert light energy to nerve impulses Retina layer: Receptor Cells • Deepest layer of retina. • Can change light energy into nerve impulses that the brain can interpret. – Without this, the brain would be completely isolated from information in the outside world. • Two different types: – Rods and cones • Visual receptor cells located in the retina. • Different in appearance and function. Comparing and Contrasting: Rods Cones • Can only detect black and white. • Have a lower absolute threshold. • Respond to less light than do cones. • Under dim light, only rods respond and you see the worlds in shades of gray. • Less of them. • Can detect sharp images and color. • Need more light. • Many cones are clustered in the fovea, where your vision is best. • The central focal point of the retina • The spot where vision is best (most detailed) Fovea Two remaining layers of the retina: • Bipolar Cells: – Middle layer of retina. – Gather information from the rods and cones and pass it on to the ganglion cells • Ganglion Cells: – Top layer of retina. – Receive info from bipolar cells and transmit it through their axons, which together form the optic nerve. Visual Processing in the Retina • The nerve that carries visual info. from the eye to the occipital lobes of the brain. Optic Nerve Parts of the Eye – Blind Spot • The point at which the optic nerve travels through the retina to exit the eye. The lack of receptor rods and cones at this point creates a small blind spot. Module 9: Sensation The Visual System: Color Vision What are the two theories of color vision? Which one offers the best explanation of how we see colors? #1:Trichromatic (three-color) Theory • Theory of color vision that says cones are “tuned” to be sensitive to red, green and blue light – All the colors we see are a combination of these three colors. • Based on work of Helmholtz and Young • Similar to the design of a color TV • Subtractive Color Mixing – When mixing colored paints, each new color SUBTRACTS (soaks up) another wavelength. – Red, blue, and yellow combine to make black paint. • Additive Color Mixing – When mixing colored lights, each new color ADDS another wavelength. – Red, green, and blue combine to make white light. Color Deficient Vision • People who lack one of the three types of cones – Usually the red or green receptors are missing • Usually referred to as color blindness • In inherited and found more in males • Sometimes people don’t even know the problem exists. #2: Opponent-Process Theory of Color • Ewald Hering’s theory that says color is processed in opponent pairs of color: – Red-green, yellow-blue, black-white • Light that stimulated one half of the pair inhibits the other half • Explains the afterimage effect Afterimage Effect: Stare at the white dot in the middle w/o blinking So…what do you see? Hearing: The Nature of Sound What is sound?? Sound • Sound, like light, comes in waves – Sound is vibration • Features of sound include: – Pitch – Hertz – decibels Pitch • A sound’s highness or lowness • Dependent on the frequency of the sound wave • Is measured as hertz (Hz) Hertz (Hz) Decibel (dB) • Determines pitch • Determines loudness • A measure of the • A measure of the number of sound height of the sound wave peaks per wave second; measures – Sometimes called amplitude “frequency” • Human hearing goes • Named after Alexander Graham from 20 Hz to 20,000 Bell. Hz Module 9: Sensation Hearing: The Structure of the Auditory System What are the major components of the auditory system? What is the function of each? • The opening through which sound waves travel as they move into the ear for processing • Ends at the tympanic membrane (eardrum) Parts of the Ear – Sound Waves Auditory Canal Tympanic Membrane (eardrum) • The tissue barrier that transfers sound vibration from the air to the tine bones of the middle ear • Can be damaged by objects in the ear or exceptionally loud noises Parts of the Ear – Tympanic Membrane • Three tiny bones that transfer sound waves from the eardrum to the cochlea • Hammer, anvil and stirrup Ossicles • A hearing organ where sound waves are changed into neural impulses • The major organ of hearing • Filled with fluid • snail shaped body tube Cochlea Oval Window • The point on the surface of the cochlea which receives the sound vibration from the ossicles • As the oval window vibrates, the fluid in the cochlea vibrates. Parts of the Ear – Oval Window Hair Cells • The receptor cells for hearing in the cochlea that change sound vibrations into neural impulses • Similar to the rods and cones within the eye • The nerve that carries sound info. from the ears to the temporal lobes of the brain Auditory Nerve Semicircular Canals • Organs in the inner ear used in sensing body orientation and balance (vestibular sense) • Relies on fluid in the canals – Spinning in circles disrupts the fluid. Parts of the Ear – Semicircular Canals Divisions of the Ear • Ear’s structure can be divided into: • The outer ear • The middle ear • The inner ear Hearing: Localization of Sound How do you identify where a sound is coming from? • Locating where sound is originating from • Done through two cues: – Which ear hears the sound first? – Which ear hears the louder sound? Other Senses: #1: Taste • Taste is a chemical sense. • Receptor cells are located primarily on the tongue and in the mouth. • Four different tastes: – Salty, sweet, sour and bitter • Damaged taste receptor cells are replaced within a few days. Supertasters • People with an abundance of taste receptors • Approximately 25% of the population Nontasters • People with a minimum of taste receptors • Taste with less intensity than the rest of the population • Approximately 25% of the population #2: Smell • Smell is a chemical sense. • Olfactory cells in the upper nasal passages detect molecules in the air. – Taste and smell interact to produce flavor. • Olfactory Cells – The chemical receptor cells for smell – Located in the nasal passages Smell Smell #3: Touch • Touch receptors are on the skin • Four basic skin senses are – Pain, warmth, cold, and pressure • All skin sensations are a combination of these four basic senses Gate-control Theory of Pain • Pain messages travel on one set of nerve fibers containing pain gates. – The gates are open when pain is felt. • Other sensory messages go through another set of fibers. • The nonpain fibers can close the pain gates to stop the sense of pain. Other Senses: Body Senses Kinesthetic Sense • The system for sensing the position and movement of individual body parts • Relies on receptor cells from the muscles and joints • One’s leg “falling asleep” is a disruption of the kinesthetic sense Vestibular Sense • The system for sensing body orientation and balance • Relies on fluid in the semicircular canals of the inner ear • Spinning in circles disrupts the fluid. Parts of the Ear – Semicircular Canals