Chapter 6 Sensation and Perception Sensation the experience of having your sense organs stimulated Perception interpreting the sensations that are experienced to recognize meaningful objects and events ex smelling something and knowing it s coffee Sensation vs Perception Evidence Sensation with out perception difficult to interpret images Same sensation different perception images with multiple interpretations Sensation Perception damaged brain areas Prosopagnosia inability to perceive faces even though vision is fine from Bottom up processing analysis beginning with sensory receptors and works up to brain s integration of sensory info sensory higher levels of processing sensation Top down processing info processing guided by higher mental processes experience expectations perception Thresholds o Psychophysics study of relationship between physical characteristics of a stimuli ex intensity and our psychological experiences of them o Absolute threshold minimum stimulation needed to detect a particular sense stimulus 50 of the time o Signal detection Signal vs background noise how and when we detect Experience expectation motivation fatigue o Subliminal stimulation Subliminal below threshold or conscious awareness Priming activation often unconscious of certain associations predisposing one s perceptions memory or response exposure at time 1 effects exposure at time 2 Difference threshold just noticeable difference JND minimum difference a person can detect between two stimulus half the time Weber s Law to be different the stimuli must vary by a constant proportion NOT AMOUNT Sensory adaptation diminishing sensitivity to an unchanging stimulus helps you perceive things because it gives a different input ex you don t smell your perfume but others do adjust to it Perceptual set a set of mental tendencies and assumptions that greatly affect what we perceive ex seeing two images in 1 Vision Transduction transforming one form of energy into another Wave length distance from one peak of one wave to peak of another determines color short blue long reddish Amplitude height of the wave tells us how bright the light is higher brighter The eye o Pupil hole in the eye allows light to enter o Iris muscle that surrounds the pupil regulates the amount of light that it s going to let enter the eye the eye o Cornea clear coating that goes over the eye focuses light and protects o Lens behind the pupil focuses light o Retina along the back of your eye where photo receptors are detect light energy and starts process of transduction o Fovea point of central focus whatever you re focusing on is the image that falls on your fovea not peripheral vision Normal vision occurs when light gets focused on fovea Nearsightedness visual image is focused on the front of the fovea Farsightedness visual image is focused behind fovea 1 Light enters the eye triggers photochemical reaction in rods and cones at the back of the retina Rod black and white active during the night bigger shapes and sizes greater concentration in periphery of fovea Cones color vision work best in day type conditions give detail highest concentration at fovea 2 Chemical reaction in turn actives bipolar cells 3 Bipolar cells active ganglion cells the axons of which converge to form optic nerves This nerve transmits info to the visual cortex via the thalamus in the brain Blind spot part of the eye where optic nerve exits no photo receptors no stimulation on that part of the eye Visual Processing Optic nerves come from eyes cross over at optic chiasm sent to thalamus and then sent to the brain ex shape angle Feature detectors nerve cells that respond to specific features of the stimulus Supercell clusters receive info from the feature detectors and respond to more complex patterns ex faces houses chairs Parallel Processing processing many aspects of a problem simultaneously more than 1 thing at a time Color vision Wavelength determines color Young Helmholtz trichromatic theory retina contains 3 different color receptors R G B all other colors formed from the combination of those three Opponent process theory opposing retinal processes allow for color vision red green yellow blue white black Visual Organization Figure and ground organization of visual fields into its objects figures and its surroundings ground what figures stand out in the ground Grouping tendency to organize stimuli into coherent groups o Proximity things that are near each other in space are perceived to be in the same group Similarity things that are alike get grouped Continuity want to perceive things as a constant sequence Connectedness pair because connected Closure filling in lines and edges that aren t there psychologically Depth perception ability to perceive the world in 3 D even though the images that fall on the retina are in 2 D ex visual cliff see how far objects are from us o Binocular cues depth cues that depend on the use of two eyes ex two pencils together o Retinal disparity difference between two images o Monocular cues depth cues available to eyes separately o Motion perception ability to perceive movement o Perceptual constancy perceiving objects as unchanging even as illumination and retinal images change o Color constancy perception of consistent color o Brightness constancy perception of consistent brighten when it s illumination varies Perceptual organization Gestalt said we perceive things as an organized whole a whole is different than the sum of its parts Hearing Audition the sense act of hearing Volume is measured in decibels threshold for humans is 0 decibels 80 90 decibels starts hearing damage Sound waves o Amplitude height loudness taller louder o Wave length pitch frequency The Ear Outer ear what we see o Pinna acts like a funnel what you hear o Auditory canal channel that sound waves travel through Middle ear Inner ear o Ear drum piece of tissue that s pulled tight as sound goes through ear causes eardrum to vibrate o Hammer anvil stirrup eardrum vibrates and sets off hammer anvil stirrup to vibrate o Cochlea coiled bony fluid filled tube sound waves travel through fluid and trigger nerve impulses goes to the thalamus and then temporal lobe Perceiving loudness of activated hair cells more hair cells louder Perceiving pitch o Place theory different sound waves trigger activity at different places along the basilar membrane closer to BM higher pitch o Frequency theory frequency of neural impulses traveling up auditory o Volley principle neural