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PSYC 100 - 4 Sensation and Perception.docx

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PSYC 100
Peter Graf

Sensation and Perception Sensation – the process by which you detect physical energy from your environment and encode it as neural signals; activation of senses Perception – the process of organizing and interpreting sensory information; influenced by your memory, motivation, emotion, and even culture; understanding these sensations Bottom-up Processing – analysis that begins with the sense receptors and works up to the brain’s processing of information; takes longer, more accurate Top-down Processing – information processing guided by higher-level processes (expectations & experiences) Psychophysics – the study of the relationship between physical energy and psychological experiences; asks questions about our sensitivity to stimuli. (ex. Light-brightness; sound- volume; pressure-weight) Absolute threshold – the minimum stimulation needed to detect ONE stimulus 50% of the time Signal detection theory – theory that our ability to DETECT absolute thresholds and SIGNALS changes based on our level of experience, focus, motivation, and fatigue Subliminal Stimulation – stimulation below one’s threshold of conscious awareness (ex. advertising) Difference threshold – the minimum difference required to tell the difference between two stimuli 50% of the time; also called 'just noticeable difference' Weber's law – difference threshold requires a constant proportion, not a constant number 1. (ex. A candy bar increases by $2, you won't buy it. A car increases by $2, you'll still buy it) Sensory Adaptation – our diminishing sensitivity to unchanging stimuli (ex. Band-aid) Selective attention – the focusing of conscious awareness on specific stimuli, ignoring other stimuli Cocktail effect – focusing in on one voice among many, like when at a cocktail party Inattentional blindness – inability to see an object/person amidst an engrossing scene Change blindness – when subjects focused on one thing don't notice something change in their environment Transduction – TRANSLATING sensory information (stimulus energies –sound waves, light waves) into neural impulses (ex. TRANSLATING the image of a DUCK into the neural message for DUCK) Phototransduction – conversion of light energy into neural impulses that brain can understand Vision and Light Energy Wavelength – distance from peak to peak of light/sound waves; determines hue (vision) or pitch (auditory) Hue (colour) – determined by light wavelength; long = red, short = blue Amplitude – height of a light/sound wave; determines brightness (vision) and loudness (hearing) Intensity – brightness; amount of energy in light waves; determined by wave's amplitude (height) Light -> cornea -> pupil (iris) -> lens -> retina -> (photoreceptors –rods & cones) -> optic nerve -> (bipolar cells -> ganglion cells) -> thalamus -> visual cortex Cornea – where light first enters the eye; protects eye; bends light to start focusing Pupil – 2nd stage; light passes through this adjustable opening; amount coming in controlled by iris 2. Iris – the colour muscle that controls pupil size and amount of light coming in Lens – 3rd stage; takes light from pupil, accommodates it (change shape), and focuses it on retina 3. Acuity – sharpness of vision; affected by distortions in lens shape 1. Nearsightedness – nearby objects are seen more clearly than distant objects 2. Farsightedness – faraway objects are seen more clearly than near objects Retina – contains sensory receptors that process visual information and send it to the brain 4. light sensitive inner surface of eye; contains rods and cones (receptor cells) and layers of other neurons (bipolar, ganglion cells) that process visual information 5. Fovea – the retina's central area of focus; cones cluster in the center here Photoreceptors: 6. Rods – peripheral receptors on the retina; sensitive to dim light 7. Cones – Centered receptors on the retina; sensitive to color and detail Optic nerve – nerve that carries neural impulses from eye to brain 8. Bipolar cells – receive messages from photoreceptors--> ganglion cells; form optic nerve 9. Ganglion cells –receives messages from bipolar cells; axons of these cells form optic nerve 10. Optic nerves connect to the thalamus in the middle of the brain Blind spot – where the optic nerve leaves the eye; no receptor cells are in this SPOT Feature Detectors – nerve cells in visual cortex respond to specific features (shape, angle, movement) Parallel processing – ability of brain to process several aspect of a situation simultaneously Colour vision Young-Helmholtz Trichromatic theory – (3-color theory); theory that retina has 3 types of cones -red, green, and blue receptors; which when stimulated in combination can produce any colour - Doesn’t explain afterimage or colour blindness Opponent-process theory – theory that opposing retinal processes (red-Green, yellow-Blue, white- Black) enable color vision; to see a color, some cells are stimulated while others are turned off; explains afterimage Color constancy – perceiving familiar objects as having consistent color, even when light changes how the object looks (context changes) Audition – sense of hearing Acoustical transduction – conversion of sound waves into neural impulses in the hair cells of the inner ear Frequency – wavelength; determines pitch; long = low pitch Amplitude – height of wavelength; determines loudness (intensity) Sound localization – sound waves strike one ear sooner and with more intensity than other ear; brain can determine location of sound Pinna -> auditory canal -> eardrum -> middle ear -> (hammer, anvil, stirrup) -> inner ear cochlea -> (basilar membrane -> hair cells) -> auditory nerves -> thalamus -> temporal lobe Outer ear: Pinna –collects sounds; Auditory canal – channels sound waves to eardrum Eardrum –tight membrane that vibrates with sounds from the auditory canal; sends vibrations along Middle ear – between eardrum and cochlea; 3 tiny bones (ossicles) - hammer, anvil, and stirrup 11. Hammer, anvil, stirrup –sends vibrations from middle ear to inner ear cochlea Inner ear –contains cochlea, semicircular canals, vestibular sacs 12. Cochlea – coiled, bony, fluid-filled tube that transduces sound vibrations to auditory signals 1. Basilar membrane –inner ear cochlea; contains hair cells (receptor cells for sound) 1. Hair cells – inner ear basilar membrane; axons form the auditory nerves Theories of Audition Place theory – Hermann von Helmholtz's theory that we hear difference pitches because sound waves hit different PLACES on the basilar membrane; explains high-pitched sounds Frequency theory – the theory that the rate of nerve impulses traveling the auditory nerve matches the FREQUENCY of a pitch; explains low-pitched sounds (because high pitches are too fast) Volley principle – neural cells alternate firing so that they achieve a combined frequency that goes much higher than what they
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