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Chapter 6

Textbook Notes - Week 6.docx

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University of Toronto St. George
Ashley Waggoner Denton

PSY 100 Textbook NotesWeek 6 Ch 5 pp 187239 sensationperception Ch 7 pp 289319 pp 327337 attentionmemoryHOW DO WE SENSE OUR WORLDS Sensation the sense organs responses to external stimuli and the transmission of these responses to the brainPerception the processing organization and interpretation of sensory signals it results in an internal representation of the stimulusThe study of sensation and perception is the study of the bodily systems that convert stimulus energy into useful informationPerception is often based on our prior experiences which shape our expectations about new sensory experiencesWhat we sense is the result of brain processes that actively construct perceptual experiences and as a result allow us to adapt to our environments details o This system can get things wrong sometimes filling in information that has not been provided but it does so in an intelligent and efficient way that still produces a meaningful understanding of what is and what happensStimuli Must Be Coded to Be Understood by the BrainTransduction A process by which sensory receptors produce neural impulses when they receive physical or chemical stimulationOur sensory organs translations of stimulis physical properties into neural impulses is called sensory codingdifferent features are coded by different neural impulse patternsSensory receptors specialized neurons in the sense organs pass impulses to connecting neurons when the receptors receive physical or chemical stimulationo Connecting neurons then transmit information to the brain in the form of neural impulses Most sensory information first goes to the thalamus Neurons in the thalamus then send information to the cortex where incoming neural impulses are interpreted as sight smell sound touch or tasteTaste o Stimuli molecules dissolved in fluid on the tongue o Receptors Taste cells in taste buds on the tongue o Pathways to Brain Portions of the facial glossopharyngeal and vagus nervesSmells o Stimuli Molecules dissolved in fluid on mucous membranes in the nose o Receptors sensitive ends of olfactory neurons in the mucous membrane o Pathway to Brain Olfactory nerveTouch o Stimuli Pressure on the skin o Receptors Sensitive ends of touch neurons in the skin o Pathway to Brain Trigeminal nerve for above the neck spinal nerves for touch elsewhereHearing o Stimuli Soundwaves PSY 100 o Receptors Pressure sensitive hair cells in cochlea of inner ear o Pathway to Brain Auditory nerveVision o Stimuli Light waves o Receptors Lightsensitive rods and cones in retina of eye o Pathway to Brain Optic nerveQualitative Stimulus Information Different sensory receptors respond to qualitatively different stimuli o Whether a light is green or red o Whether a sound is from a guitar or piano o Whether a taste is salty of sweetQuantitative Stimuli Information Coded by the speed of a particular neurons firing o A rapidly firing neuron is responding at a higher frequencybrighter light louder sound heavier weightReceptors provide coarse coding o Sensory qualities are coded by only a few different types of receptors each of which responds to a broad range of stimuli o Combined firing by different receptors at different rates allows us to tell the difference between for example lime green and forest green or a pinch and a shovePsychophysics Relates Stimulus to ResponsethPsychophysics is a subfield developed during the 19 century by Ernst Weber and Gustav Fechner and it exams our psychological experiences of physical stimuli It assesses how much physical energy is required for our sense organs to detect a stimulus and how much change is required before we notice it SENSORY THRESHOLDSSensory organs constantly acquire information from the environment much of which you do not noticeAbsolute Threshold the minimum intensity of stimulation that must occur before you experience a sensation or the stimulus intensity detected above chance o For hearing this is the faintest sound a person can detect 50 percent of the time o Taste one teaspoon of sugar in 75 litres of water o Sight A candle flame seen at 50 km on a dark clear nightDifference Threshold the just noticeable difference between two stimulithe minimum amount of change required for a person to detect a difference o Difference threshold increases as the stimulus becomes more intense o Difference between 20 g and 40 g is easily detectable but the difference between 2 kg and 202 kg is not as easy to detectWebers Law The just noticeable difference between two stimuli is based on a proportion of the original stimulus rather than on a fixed amount of differenceDelta IIa constantfor example you can detect 1 candle in a group of 10 candles 11001 and thus you would need 10 candles to detect a difference in brightness when you have 100 candlesSIGNAL DETECTION THEORY
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