PSYCH CH. 4.doc

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Department
Psychology
Course
PSY100H1
Professor
Dax Urbszat
Semester
Winter

Description
Chapter 4 Sensation and PerceptionSensationthe stimulation of sense organsPerceptionthe selection organization and interpretation of sensory inputSensation involves the absorption of energy such as light or sound waves by sensory organs such as ears and eyesPerception involves organizing and translating sensory input into something meaningfulPsychophysicsPsychophysics the study of how physical stimuli are translated into psychological experienceImportant contributor Gustav FechnerThresholdsSensation begins with a stimulus any detectable input from environmentThreshold the dividing point between energy levels that do and do not have a detectable effectAbsolute threshold for a specific type of sensory input the minimum amount of stimulation that an organism can detectoDefine the boundaries of an organisms sensory capabilitiesoHowever the absolute threshold is not absoluteie as stimulus intensity increases subjects probability or responding to a stimuli gradually increasesJust Noticeable Difference JNDJND the smallest difference in the amount of stimulation that a specific sense can detectoVery similar to absolute thresholdoAbsolute thresholdJND from nothing no stimulus inputJNDs vary by senseThe smallest detectable difference is a fairly stable proportion of the size of the original stimulusWebers lawothe size of a just noticeable difference is a constant proportion of the size of the initial stimulusoConstant proportion is called the Weber fractionoThis law applies to all sensesoDifferent fractions apply to different types of sensory inputPsychophysical ScalingFechners law the magnitude of a sensory experience is proportional to the number of JNDs that the stimulus causing the experience is above the absolute thresholdoConstant increments in stimulus intensity produce smaller and smaller increases in the perceived magnitude of sensationoEg in a dark room with a single lamp that has three bulbs of the same wattage you turn on one light bulb the difference against the completely dark room is striking as ndyou turn on the 2 bulb the amount of light is doubled but the room does not seem rdto be twice as bright by the 3 bulb you barely notice the differenceThis means that perceptions cant be measured on absolute scalesIn terms of sensory experience virtually everything is relativeSignalDetection TheorySignaldetection theory the detection of stimuli involves decision processes as well as sensory processes which are both influenced by a variety of factors besides stimulus intensityoYour responses will depend in part on the criterion you set for how sure you must feel before you reactoYour performance will also depend on the level of noise in the systemNoise comes from all of the irrelevant stimuli in the environment the more noise the harder to pick up a weak signalPerceptions without AwarenessSubliminal perception the registration of sensory input without conscious awarenessoSubliminal means below thresholdThere has been research that proved perception without awareness CAN take placeSubliminal stimulation generally produces weak effects thus there is little reason for concern about the threat of subliminal persuasionSensory AdaptationSensory adaptation a gradual decline in sensitivity due to prolonged stimulationoWith continued exposure to the stimuli your sensitivity to it decreasesoIt is an automatic builtin processoAllows people to ignore the obvious and focus on changes in their environment that may signal threats to safety
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