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Chapter 5

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PSYC 100
James Mac Dougall

Chapter 5Sensation and PerceptionHow do we sense our worldsSensationthe sense organs responses to external stimuli and the transmission of these responses to the brainoLight air vibrations odoursdetectionPerceptionthe processing organization and interpretation of sensory signals it results in an internal representation of the stimulusoConstruction of useful and meaningful information about a particular environmentSteps Stimulus Sensation Sensory Coding PerceptionPerception often based on prior experiencesWhat we sense see hear taste touch smell is the result of brain processes that actively construct perceptual experiences allowing us to adapt to our environments detailsStimuli must be coded to be understood by the brainSensory codingsensory organs translations of stimulis physical properties into neural impulsesDifferent environmental features coded by different neural impulse patternsBrain does not process raw stimuli so it must be translated into chemicalelectrical signals for the brain to interpretTransductiona process by which sensory receptors produce neural impulses when they receive physical and chemical stimulationoSensory receptors specialized neurons in a sense organ pass impulses to connection neuronsoConnecting neurons transmit information to brain in form of neural impulsesoFirst goes to thalamus then to the cortex to be interpreted as sight smell touch tasteSenseStimuliReceptorsPathways to BrainTasteMolecules Taste cells in taste buds Portions of facial dissolved in fluid on the tongueglossopharyngeal vagus on the tonguenervesSmellMolecules Sensitive ends of Olfactory nervedissolved in fluid olfactory neurons in the on mucous mucous membranesmembranes in the noseTouchPressure on the Sensitive ends of touch Trigeminal nerve for touch skinneurons in skinabove the neck spinal nerves for touch elsewhereHearingSound wavesPressuresensitive hair Auditory nervecells in cochlea of inner earVisionLight wavesLightsensitive rods and Optic nervecones in retina of eyeBrains need quantitative and qualitative information about the stimulusoQualitativecan identify differences because different sensory receptors respond to qualitatively different stimuli and neurons are firing in different combinationsoQuantitativedifferences in stimuli are coded by the speed of a particular neurons firingmore rapidly firing neurons respond at higher frequenciesReceptors provide coarse codingsensory qualities are coded by only a few different types of receptorseach responding to broad stimuli rangeoCombined responses of different receptors firing at different rates allow us to tell difference between themPsychophysics relates stimuli to responseRelationship between worlds physical properties and how we senseperceive themPsychophysicssubfield by Weber and Fechner examines psychological experiences of physical stimulioHow much physical energy required for our sense organs to detect a stimulusoHow much change is required before we notice the changeSensory thresholdsoAbsolute thresholdminimum intensity of stimulation that must occur before you experience a sensationTaste1 teaspoon of sugar in 75 L of waterSmellone drop of perfume diffused in the entire volume of 6 roomsOucha flys wing falling on your cheek from 1 cm awayHearingthe tick of a clock 6 meters away in quiet conditionsVisioncandle flame seen 50 km away on dark clear nightoDifference thresholdjust noticeable difference between two stimuliminimum amount of change required for a person to detect a differenceWebers Lawstates the just noticeable difference between two stimuli is based on a proportion of the orignal stimulus rather than a fixed amount of differenceDIIksignal detection theorya theory of perception based on the idea that the detection of a faint stimulus requires a judgmentit is an allornone processosensory thresholds are not absolute since human judgment can be impairedoseries of trials where stimulus presented in only some trialsoeach trialparticipants state whether they sensed the stimulus or notohitsignal presented and observer detects itomisssignal presented and observer doesnt detect itofalse alarmsignal not presented but observer detects itocorrect rejectionsignal not presented and observer doesnt detect itoresponse biasparticipants tendency to report detecting signal in ambiguous trial
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