Myers EXPLORING PSYCHOLOGYSensationSlide 3SensationSensation: Basic PrinciplesSensation: ThresholdsSlide 7Slide 8Now you see it, now you don’t!VisionSlide 11Slide 12Vision: Physical Properties of WavesSlide 14Slide 15Retina’s Reaction to Light- ReceptorsRetina’s Reaction to LightSlide 18Vision: ReceptorsPathways from the Eyes to the Visual CortexVisual Information ProcessingSlide 22Slide 23Slide 24Slide 25Slide 26Color-Deficient VisionOpponent Process: Afterimage EffectMyers EXPLORING PSYCHOLOGYModule 14Introduction to Sensation and Perception: VisionJames A. McCubbin, PhDClemson UniversityWorth PublishersSensationSensationthe process by which our sensory receptors and nervous system receive and represent stimulus energyPerceptionthe process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and eventsSensationOur sensory and perceptual processes work together to help us sort out complex imagesSensationBottom-Up Processinganalysis that begins with the sense receptors and works up to the brain’s integration of sensory informationTop-Down Processinginformation processing guided by higher-level mental processesas when we construct perceptions drawing on our experience and expectationsSensation: Basic PrinciplesPsychophysicsstudy of the relationship between physical characteristics of stimuli and our psychological experience of themLight- brightnessSound- volumePressure- weightTaste- sweetnessSensation: ThresholdsAbsolute Threshold minimum stimulation needed to detect a particular stimulus 50% of the timeDifference Thresholdminimum difference between two stimuli required for detection 50% of the timejust noticeable difference (JND)Sensation: ThresholdsSubliminalwhen stimuli are below one’s absolute threshold for conscious awareness0255075100Low AbsolutethresholdMediumIntensity of stimulusPercentageof correctdetectionsSubliminal stimuliSensation: ThresholdsWeber’s Lawto be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)light intensity- 8%weight- 2%tone frequency- 0.3%Now you see it, now you don’t!Sensory Adaptation- diminished sensitivity as a consequence of constant stimulationVisionTransductionconversion of one form of energy to anotherin sensation, transforming of stimulus energies into neural impulsesWavelengththe distance from the peak of one wave to the peak of the nextVisionHuedimension of color determined by wavelength of lightIntensityamount of energy in a wave determined by amplitudebrightnessloudnessThe spectrum of electromagnetic energyVision: Physical Properties of WavesShort wavelength=high frequency(bluish colors, high-pitched sounds)Long wavelength=low frequency(reddish colors, low-pitched sounds)Great amplitude(bright colors, loud sounds)Small amplitude(dull colors, soft sounds)VisionVisionAccommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retinaRetina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual informationRetina’s Reaction to Light- ReceptorsRodsperipheral retina receptorsdetect black, white and grayfor peripheral or twilight conditionsConesreceptors near center of retina fine detail and color visionfor daylight or well-lit conditionsRetina’s Reaction to LightOptic nervenerve that carries neural impulses from the eye to the brainBlind Spotpoint at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located thereVision: ReceptorsReceptors in the Human EyeCones RodsNumberLocation in retinaSensitivity in dim lightColor sensitive? YesLowCenter6 millionNoHighPeriphery120 millionPathways from the Eyes to the Visual CortexVisual Information ProcessingFeature Detectorsnerve cells in the brain that respond to specific featuresshapeanglemovementStimulusCell’s responsesVisual Information ProcessingParallel Processingsimultaneous processing of several aspects of a problem simultaneouslyVisual Information ProcessingTrichromatic (three color) TheoryYoung and Helmholtzthree different retinal color receptorsredgreenblueVisual Information ProcessingOpponent-Process Theory- opposing retinal processes enable color vision“ON” “OFF”red greengreen red blue yellow yellow blue black whitewhite blackVisual Information ProcessingColor ConstancyPerceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the objectColor-Deficient VisionPeople who suffer red-green dificiency have trouble perceiving the number within the designOpponent Process: Afterimage
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