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HOW MUCH OF OUR EXPERIENCE OF THE WORLD IS REAL? AND HOW MUCH IS OUR INTERPRETATION BASED ON EXPERIENCE? SENSATION & PERCEPTION (PSYCHOPHYSICS) TWO PROCESSES THAT WORK TOGETHER Sensation Perception The process of attending to and taking stimuli from the environment. the environment can be our own bodies. “Bottom-up” processing. The process of interpretation and organization of sensory information. May be as much as 90% stored knowledge/memory. “Top-down” processing. TOP-DOWN PROCESSING Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT http://www.psywww.com/intropsych/ch07_cognition/top-down_and_bottom-up_processing.html BOTTOM-UP PROCESSING 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.” MAKING SENSE OF COMPLEXITY Our sensory and perceptual processes work together to help us sort out complex images. Need a volunteer OUR SENSES…. • Vision • Hearing • Taste • Touch (pain, temperature & proprioception) • Smell • Vestibular (body balance/equilibrium) • Kinesthetic (position/movement) THRESHOLDS MEASURING SENSATION • Absolute threshold= the minimum amount of a stimulus you can detect (50% of the time) • Just noticeable difference (JND)=the amount of change in stimuli (increase or decrease) before it becomes noticeably different. It is the smallest amount of difference detected 50% of the time. • Weber’s Law= The amount of change needed to produce JND is in proportion to the original stimulus’s intensity. DETECTING STIMULI CAN BE CHALLENGING! • Our senses act as a data reduction system. This allows us to focus on specific stimuli when there is a great deal of background stimuli. Example: air conditioner/heat vent, traffic sounds, bad smell, swimming in the ocean.. • Repeated exposure to any stimulus can desensitize someone so that they no longer attend to it= habituation. • Our sensory experience is not stimulus alone. Feelings, expectations & motivation all influence whether you experience a stimulus. Signal detection theory explains the relationship between stimuli and motivation. • Hit- Miss- False alarm (Your phone…….) SELECTIVE AND DIVIDED ATTENTION Selective Attention Cocktail party effect Divided Attention Inattentional blindness= Gorilla example Are you a multi-tasker? Can the brain multi-task? PERCEPTUAL DEFENSE=EXPLAINS WHY DETECTING STIMULI MAY BE CHALLENGING Whore Rape Bitch Penis Wharf Rope Batch Pencil ALL SENSES TAKE STIMULI AND CHANGE (TRANSDUCE) IT INTO A SIGNAL UNDERSTOOD BY THE BRAIN • Receptor cells take energy and change it into a neurological signal which travels to the thalamus. • Except for smell • (which has a direct root to the frontal lobe) • Senses interact with each other. THE EYE Receptors: Rods=night/peripheral. Cones= daylight/color(located in the Fovea. Retina= contains photoreceptors Iris= controls size of pupil Pupil= Opening Lens=bends light/focus Optic nerve=blind spot THEORIES OF COLOR (HUE) Trichromatic Theory (Young-Helmholtz) • Three different types of color receptors set to identify redblue-green • Different rates of neural processing allow us to see “other” colors Opponent Process Theory • Two kinds of cones • One relates to red & green • One relates to blue & yellow • Rods relate to black & white • When one color is excited- the other is inhibited. This helps explain afterimages THE EAR (AUDITION)SOUND WAVES TRANSDUCED BY RECEPTORS LOCATED ON THE MEMBRANE IN THE COCHLEA Process:Sound waves- auditory canal-vibrates the eardrum- which vibrates three ossicles-pass into the cochlea (fluid) Sensory information carried to the auditory cortex. HAIR CELLS Inner ear hair cells Damaged inner ear hair cells CHARACTERISTICS OF SOUNDS • Frequency= pitch( high or low sounds) • Amplitude= loudness(volume) • Place theory= differences in pitch from stimulation in different areas of the basil membrane • Frequency theory= differences in pitch are due to speed of neural impulses CHEMICAL SENSES: NOSE=OLFACTORY • Receptors located along the olfactory bulb. • Olfactory cells stimulated by gases • Over 100 different receptor sitescombinations produce 10,000 + different scents THE TONGUE GUSTATORY(CHEMICAL) SYSTEM • Chemical-sensitive receptors located in taste bud (clusters) • Taste buds regenerate. • Decline with age. • Stimulus must be dissolved. • Other influences on taste: smell, touch/texture, temperature BODY SENSES=SENSES OF TOUCH • Pressure (only skin sense with identifiable receptors) • Warmth • Cold • Pain PAIN=IT’S YOUR BODIES WAY OF TELLING YOU SOMETHING IS WRONG… • Pain is property of the senses and the brain (we all experience it differently) • Phantom Limb Sensation • Two systems- carry nerve fibers from skin to spine • A-delta fibers= sharp, fast pain • C-fibers=dull pain (influenced by limbic system) • Gate-control theory of pain (small fibers “open” the gate- large fibers “close” the gate) YOU HAVE MILLIONS OF POSITION & MOTION SENSORS ALL OVER YOUR BODY! Kinesthetic System • The sense of our body part’s position & movement Vestibular System • Monitors the head (and body) position and movement thru the inner ear.