PSY280 Final Exam Notes

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Kristie Dukewich

PSY280H1 Final Exam Notes made by Man Lai Ho Lecture 1Experience o Perception act of giving meaning to sensationTopdown processing knowledgedrivenEg Ratman demonstration o Presentation of first ratlikemanlike picture influences observers perception of second picture o Sensation ability to detect stimulusBottomup processing datadriven o Only your own sensory experience is accessible to you perception is a private experiencePerceptual process sequence of steps leading from environment to perception recognition of a stimulus and action with regard to the stimulus o Environmental stimulus stimulusin external environmentEx Light in the environment o Stimulus transformedPrinciple of Transformation perception of stimuli and responses created by stimuli are transformedchanged between environmental stimulus and perceptionPrinciple of Representation everything a person perceives is based on representations of stimuli on the receptors and in the nervous system not on direct contact with stimuliEx Info from object is carried by light reflected off object travels through atmosphere and focused on eyes optical system passes through cornea lens and on receptors on retina o Receptor processesSensory receptors cells specialized to respond to specific environmental ENTransduction transformation of environmental EN into electrical ENEx Visual receptorsRod and cone receptors lining back of eye transform light EN Into electrical EN influence what we perceive o Visual pigment lightsensitive molecule in rod and cone outer segmentsReacts to light and generates electrical response in receptors o Neural processingAfter transduction electrical signals enter network of neuronsNetwork of neuronsTransmit signals from receptors to brain within brain multiple routesProcess signals amplification reduction travel in opposite directions blockedPrimary receiving areas areas of cerebral cortex that first receive most of the signals initiated by senses receptors A Occipital lobe VisionB Parietal lobe Skin Senses o Termination point of the dorsal wherehow stream of visual processingC Frontal lobe Action o Receives signals from all senses coordination of info PSY280H1 Final Exam Notes made by Man Lai Ho o Language thought memory and motor functioningD Temporal lobe Hearing o Termination point for ventral what stream of visual processing o Fusiform face area and extrastriate area o Perception conscious sensory experience o Recognition ability to place an object in a category that gives meaningEg Visual form agnosia inability to recognize objects o Action motor activities and also lack of action o Unidirectional from Environmental stimulus to Receptor processes Bidirectional from Receptor processes to ActionSteps can cooccurhappen in reverse direction Action can change how we perceiverecognizeApproaches to study of perception o Psychophysics psychophysical determine how persons perception is related to stimuli in environmentRelationship between physical stimuli and psychological experienceStimulus Intensity I on xaxis Sensation magnitude S on yaxisLinear Exponential or Logarithmico Eg Exponential functionIntensity of Pressure vs PainOblique effect enhanced sensitivity to verticallyhorizontally oriented visual stimuli compared to obliquely oriented slantedEg Fine line test o Physiological determine how a persons perception is related to physiological process occurring within the person o Cognitive influences on perception knowledge memories expectation that a person brings to a situation influences hisher perceptionMeasuring Perception o Absolute threshold minimum stimulus intensity necessary for stimulus to be detectedIe Is A presentGustav Fechner 1860 Classical psychophysical methodsMethod of limits experimenter presents sequences of stimuli in ascending and descending order o Eg low tone deep beepTypical threshold is between 97dB and 99dB intensitySeveral trials alternating between starting highlow in intensityo Thresholdaverage of the crossover valuesMethod of adjustments participant adjusts stimulus intensity in a continuous manner until participant detects stimulus o Eg Adjustable knob for starting highlow o Thresholdaverage of points at which it is barely audible toneMethod of constant stimuli number of stimuli with different intensities are presented repeatedly in a random order o Data points collected by determiningof trials observer detected each intensity o Thresholdintensity that results in detection on 50 of the trials o Most accurate but time consumingPerception in human beings is never perfectgradual detection of stimulus o Ideally step detectionof detection bounce straight up upon reaching absolute threshold o Difference threshold minimum detectable differences between two stimuliIe Is A biggerbrighterheavier than BDepends on where you start More difficult to determine addition of 1 penny if start with 100 pennies instead of 1 penny difference threshold2 for weight PSY280H1 Final Exam Notes made by Man Lai HoJND just noticeable difference change in intensity between 25 brighter and 75 brighterdifference thresholdTarget Light intensity I on xaxis Percentage brighter on yaxisWebers Fraction IkI I JND kWeber Fraction 08 light Ireference intensity o Magnitude estimate subject assigns numbers to a stimulus that are proportional to perceived magnitude of stimulusIe On a scale of 1 to 10 how bright is APerceived magnitude varies with individual intensity is physical measure set valueStevens Power Law n PKS Pperceived intensity Kconstant Sstimulus intensity nexponent slope of logn1 linearn1 exponential response expansion o eg Electric shocksn1 logarithmic response compression o eg brightnessLog both sides function converted from nonlinear to linear o Log stimulus intensity on xaxis log magnitude estimate on yaxis o Phenomenological method determine relationship between stimuli and perception in which observer describes what heshe perceives people with brain damage o Visual search procedure in which persons task is to find particular element in a display containing a number of elements o Reaction time time between presentation of stimulus and subjects response to the stimulusMeasure of speed of processingLecture 2Signal detection Theory detection of a stimulus depends both on participants sensitivity to the stimulus and on the participants response criteria o In a detection experiment Vivian says yes to 70 of trials while Pavel says yes to 90 of trialsThreshold at 50 is at a lower light intensity for Pavel than Vivian o Response criteria decisionmaking under conditions of uncertaintyConservative Say no more Vivian Liberal Say yes more PavelCan be adjusted by using rewards Stimulus Yes No Present Hit Miss Absent False alarm Correct rejection o ROC receiver operating characteristicPlots a persons proportion of hits on yaxis vs false alarms on xaxis for different response criteria Conservative Neutral LiberalSensitivity can be evaluated100 hits for stimulus present 100 false alarms for stimulus absentIf curves superimpose on each otherperceptual sensitivity is the same but response criteria is differentIf one is more perceptually sensitive than other one curve above the otherResponse criteria is orthogonal unrelated to perceptual sensitivity ability to detect faint stimulusVision o Sensory systems thought of as being nearfar with respect to detecting external stimuli o Dominant sensory system in humans and takes up aboutof brain for processing o Lightreceptorsafferent neuronsBrainknowledge
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