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SENSATION & PERCEPTION Do Now: Could you live without any one of your senses? BASIC PRINCIPLES Sensation: sensory receptors & nervous system receive and represent information from the environment Perception: process of organizing and interpreting sensory info Recognize meaningful objects and events PROCESSING Bottom-Up Processing Sensory receptors to brain’s integration of sensory info Top-Down Processing Constructs perceptions from the sensory from sensory input by drawing on experience and expectations TRANSDUCTION Sensory System Receives stimuli Transforms it into neural stimulation Delivers info to brain This process of changing one form of energy into something your brain can use is transduction What are some of the strengths and weaknesses of this system? THRESHOLD Right now we are being hit with tons of different waves (xrays, radio waves, uv and infrared light, sound waves). Why don’t we notice these? Absolute Threshold The least amount of stimulation needed to detect a stimulus 50% of the time i.e. Hearing tests Signal Detection Theory Predicts when we will detect weak signals (hits/false alarms) Tests sensations but also our expectations Subliminal: stimuli you detect less than 50% of the time Prime: activation of an association and thereby predisposing you to form a memory or response Often unconscious of this Image test BREAK TIME! You’re driving a bus with 12 passengers. At your first stop, 6 passengers get off. At the second stop, 3 get off. At the third stop, 2 more get off but 3 new people get on. What color are the bus driver’s eyes? Can we be controlled by subliminal messages? DIFFERENCE THRESHOLDS To function we need: Low enough absolute thresholds so we can see, hear, taste, feel, and smell important stimuli Need to know the small differences among stimuli Difference Threshold: The just noticeable difference Minimum dif. a person can detect between any two stimuli half the time Weber’s Law: For the average person to perceive a difference, 2 stimuli must differ by a constant proportion. Ex. Two lights must differ in intensity by 8% Sensory Adaptation Decrease in sensitivity as a result of constant stimulation We perceive the world not exactly as it is, but as it is useful for us to perceive it. What are some examples? How do TV editors do this? YouTube videos use this to their advantage? Perceptual Set A set of mental tendencies and assumptions that impact what we perceive (top-down) What determines this? Schemas Schemas are experiences that form concepts that help us organize and interpret unfamiliar information How do we know what pronoun to use for a newborn? Context Effects A stimulus might trigger different perceptions because of our different mental sets but… …also because of the context Eel is on the wagon or eel is on the orange Emotion & Motivation Sad music Water bottle seems closer when thirsty If you’re tired when walking the destination seems further VISION LIGHT ENERGY Only see a small portion of all rays Other organisms see different spectrums Wavelength Hue Distance from one peak to next Color we experience Determined by wavelength Intensity Amount of energy Amplitude Brightness THE EYE Pupil Iris Small adjustable opening Light passes through Controls pupil Colored muscle Light/ Emotions Lens Focuses on incoming light into an image Accommodation: adjusts curvature Retina Multilayered image on eye’s inner surface THE RETINA (CON’T) Receives info as upside down Sends neural impulses – brain perceives this images as right side up 2 types of cells Rods Retinal cells detect black, white, gray Use at night and for peripheral vision Share bipolar cells Cones Retinal cells near center Color, fine detail, daylight (fovea- point of central focus on retina) Each has one bipolar cell Bipolar cells send to ganglion cells: form optic nerve Carry info to brain (thalamus to distribute) Where optic nerve leaves eye there are no cells: blind spot Brain fills in the hole VISUAL INFORMATION PROCESSING Retina begins processing info Frog’s eye: see “fly like” movement fight/flight response Feature Detection Respond to specific features Cortical areas respond to details What if this area was damaged? Brain’s face processing is different than object perception Cells are specialized: movement, gaze, posture, etc. Parallel Processing Doing many things at once Divide a scene Facial recognition Blind sight: say they see nothing but guess correctly COLOR VISION 2. Item rejects color we perceive them Color is mental construction Young Helmholtz Thrichromatic Theory 1. 3 types of color receptors (red-green-blue) Sensitive to one color Ex. Yellow stimulates red and green receptors Deficiency: lack receptors Opponent Processing Theory Red-green, yellow-blue, white-black Allows color vision to happen Receptor turns on with red and off with green VISUAL ORGANIZATION Gestalt: organization of sensations in a “whole” Filter info and make meaning Form Perception Figure and ground Grouping Order and form to stimuli Proximity (close), Continuity (smooth), Closure (fill in gaps) Depth Perception Estimate object’s distance Binocular cues Two eyes to judge distance Retinal Disparity: difference between two images; closer object is determined Monocular cues Depth cues available to each eye Motion perception Phi Phenomenon: Lights can recreate this PERCEPTUAL CONSTANCY Top-down Perceive objects as unchanging, even if illumination and retinal image change Color and Brightness Constancy Shape and Size Constancy VISUAL INTERPRETATION Perceptual adaptation Will adapt given new visual input e.g. glasses HEARING (AUDITION) Sound waves: amplitude = loudness frequency = pitch measure in decibels The Ear Outer ear – eardrum (vibrates) Middle ear – hammer, anvil, stirrup Inner ear – cochlea (oval window): vibrates and fills with fludid Bends hair cells(auditory nerve) sends to auditory cortex HEARING DAMAGE Sorineural Hearing Loss nerve deafness Conduction Hearing Loss rare damage to mechanical system Treatment Cochlear implant Restores hearing with nerve damage TOUCH Crucial to development (needed as an infant) Paiin Nocireceptors: dects harmful temp, pressure, chemicals Gate-Control Theory Spinal cord either blocks or allows pain to pass to the brain What holistic approaches help to inhibit pain? Physical Phenomena Endorphins Phantom limb sensations Psych influences Social-cultural influences Controlling pain TASTE Sweet Salty Sour Bitter Umami Sensory interaction One sense influences another SMELL Women have better sense of smell What types of factors might contribute to having a worse sense of smell? Associate smell with memories Learned Associations BODY POSITION & MOVEMENT