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Chapter 4

Chapter 4 Notes Notes on chapter 4 in point form

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Wilfrid Laurier University
Eileen Wood

Chapter 4 Psychology Notes By Yen HoangSensation the stimulation of sense organsThe process through which the senses detect visual auditory and other sensory stimuli and transmit them to the brainInvolves the absorption of energy such as light or sound waves by sensory organs such as the eyes or ears Perception the selection organization and interpretation of sensory inputThe process by which sensory information is actively organized and interpreted by the brainInvolves organizing and translating sensory input into something meaningful such as your best friends face or other environmental stimuliPsychophysics Basic Concepts and IssuesPsychophysics the study of how physical stimuli are translated into psychological experienceThresholds looking for limits o Sensation begins with a stimulus any detectable input from the environment o A threshold is a dividing point between energy levels that do and do not have a detectable effectAn absolute threshold for a specific type of sensory input is the minimum amount of stimulation that an organism can detectThey define the boundaries of an organisms sensory capabilities o The difference between being able to perceive a stimulus and being able to just barely perceive itResearchers had to arbitrarily define the absolute threshold as the stimulus intensity detected 50 of the timeWeighing the difference the JND o Difference threshold the smallest increase or decrease in a physical stimulus that is required to produce the just noticeable difference JND in sensation that is detectable 50 of the timeJND is the smallest difference in the amount of stimulation that a specific sense can detect As stimuli increase in magnitude the JND becomes larger Webers law states that the size of a just noticeable difference is a constant proportion of the size of the initial stimuluso This constant proportion is called the Weber fractionAmount of increase needed to make a differenceIe if you are carrying 20 kg 1 additional gram will not make a difference o Whereas if youre carrying only 20 g 1 g will make a difference o Webers law applies not only to weight perception but to all of the senses The flaw with these classic measures o Focus on the physical stimulusHow strongweak it isHow muchlittle there is o What about individual variationsIndividuals differ from each otherIndividuals can differ depending on contextPsychophysical scaling o Feschners law states that the magnitude of a sensory experience is proportional to the number of JNDs that the stimulus causing the experience is above the absolute thresholdConstant increments in stimulus intensity produce smaller and smaller increases in the perceived magnitude of sensation o Perceptions cannot be measured in absolute scalesIn the domain of sensory experience virtually everything is relativeSignaldetection theory o The fact that perceptions cant be measured on absolute scales applied not only to sensory scaling but to sensory thresholds as well o Signaldetection theory proposes that the detection of stimuli involves decision processes as well as sensory processes which are both influenced by a variety of factors besides stimulus intensityDetection of sensory stimulus involves noticing a stimulus from background noise and a decision about whether the stimulus is presentDecision the probability of stimulus occurrence and potential gainloss with deciding whether the stimulus was presentnotReal life example picking up your cousin whom youve never met at the airport having only a descriptionold photoThere are four possible outcomes o Hits detecting signals when theyre present o Misses failing to detect signals when theyre present o False alarms detecting signals when theyre not present o Correct rejections not detecting signals when they are absentPerception without awareness o Subliminal perception the registration of sensory input without conscious awareness Is it possibleYes and no o If just at threshold it works but very very tinySubliminal stimulation generally produces weak effects o Below threshold technically not possibleSensory adaptationo The process of sensory adaptation is yet another factor that influences registration of sensory input o Sensory adaptation is a gradual decline in sensitivity due to prolonged stimulation
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