PSYCH100H EXAM 2NATIVISM = some knowledge is innateEMPIRICISM = some knowledge acquired through experimental learningDistal stimulus = how object actually appearsProximal stimulus = physical stimulation available to be measuredThe distal stimulus is inferred based on info from proximal stimulusPsychophysics = the study of relationships btw the distal stimulus and our sensationsLeads to measurements of presumed sensations & determinations of thresholdsPerceptions are generated by combining traditional sensory psychAbsolute Threshold = minimum stimulus energy needed for detection 50% of the timeDifference Threshold / Just Noticeable Difference = change of a stimulus needed for detection 50% of the timeThe JND is a constant fraction of a standard: ΔI / I (Weber’s Law)Fechner’s Law says that stimulus strength & perceived stimulus strength display a logarithmic relationshipEqual increases in stimulus magnitude yield exponentially lower growth rates of sensationSignal Detection TheoryExperiments are impacted by response biases: must distinguish btw hits, misses, & false alarmsHit = correct identification of the signalMiss = no identification of signalFalse Alarm = incorrect identification of signalMore guessing = more of BOTH hits and false alarmsReceiver-Operator Curve plots false alarms vs. hits at diff stimulus intensities while manipulating response biasFor hits ABOVE threshold, there is a greater hit rateFor hits BELOW threshold, there is a greater false alarm rateTransduction = Conversion of energy into another form of energy (ex, light to nerve action pot)Muller’s Theory = doctrine of specific nerve energies  only partially correct!Specificity Theory = diff sensory qualities are signaled by diff neuronsAcross Fiber Pattern Theory = overall pattern activation in a set of nerve fibers codes sensory qualities (ex, olfactory system)VISION AND LIGHTVisible light = only a small part of the electromagnetic spectrumEncompasses large fraction of energy reaching earth’s surfaceWavelength corresponds to color, light intensity corresponds to brightness Light is focused by a convergent lensPrincipal axis = line that runs through center of curvePrincipal focus = where rays convergeForms images by refractive propertiesAs object gets closer, image enlarges & moves farther from focal planeImage cannot be formed if object is at focal distanceCornea & lens focus light on the retinaNeural tissue at back of eye makeup optic nerveAccomodation occurs when the lens BULGES to focus NEAR objectsFLATTENS for FAR objectsRefractive errors impair perceptions of distanceMyopia = concave lens correctionFarsighted = convex lens correctionRods contain rhodopsinFunction in low levels of lightCones contain photopsinsFunction during daylightContained in the fovea (highest density of photoreceptors)Rods/cones differ in time course of dark adaption & max sensitivityRods & cones are connected with bipolar and ganglion cellsGanglion cells receive both excitatory and inhibitory input edge enhancementLateral inhibition = ability of an excited neuron to reduce the activity of its neighbors (LATERAL relationships)COLOR VISIONTri-chromatic Theory (Helmholz) = color vision is generated by 3 wavelength sensitive receptorsDoes not account for uniqueness of yellow, color blindness, or afterimagesHering proposed 3 visual opponent-process channelsRed-greenBlue-yellowBlack-whiteEach photoreceptor responds to a range of wavelengthsWavelength corresponds to pattern of photoreceptor responsesExistence of several types of opponent-process ganglion cellsWhite light:All cones & rods have strong responseRed light:Red strong response, green medium response, blue weak response, rods weak responseGreen light:Red medium response, green strong response, blue med response, rods med Blue light:Red weak response, green medium response, blue strong response, rods weakYellow Light:Red strong response, green strong response, blue med response, rods strong responseYellow color is created by adding middle & long wavelengths (summation) to same bipolar cellsColor Weakness / BlindnessGenes for L and M opsins (red and green) are both on x-chromGene for S opsin (blue) is autosomalExtra gene copies do not impair color visionPERCEPTIONEmpiricists (Locke) believe perception = associations btw simple sensationsNativists (Kant) believe perception is guided by a priori mental processesNativism v. Empiricism:Do we LEARN to use multiple cues in proximal stimulus to infer distal 3D structure?Or do INNATE perceptual mechanisms allow us to do this?Depth perception:Uses monocular and binocular cuesBinocular Disparity= difference btw two retinal images; decreases when fartherInterposition = monocular cue (spatial inferences)Retinal image is flatRequires either learned or unlearned INFERENCE of depthTexture gradient density increases as objects move farther awaySize of retinal image increases when closer—size of objects allow distance inferencesGestalt Psychology = “Pattern”Innate mental processes organize stimuli into patternsLaw of Pragnanz = perception favors symmetry and simplicityBelieve that we innately separate figure and background in perceptionReification = generating aspects of perception; creating an image by “filling in the gaps”Apparent motion (“beta”) is sometimes indistinguishable from real motion (“phi)Similarity & proximity reinforce idea of innatenessContinuity = patterns in sensory persist in the mindCommon fate = elements moving in same direction together are perceived as a unitInvariance = common objects retain their shapes when moving or rotatingGood continuation = simplest interpretation is madeClosure = assumption of “filling the gap” to create a shapeMEMORYImplicit = memories we access w/out being consciously aware of doing so (motor skills)Explicit = memories we’re consciously aware of accessingepisodic, semantic, spatial, genericinvolves both short and long term memoryEncoding = the form info is placed in during learningStorage = the record made of this info in the brainRetrieval of this info is studied by recall or recognitionShort term memory = temporaryCapacity is about 2-7 itemsMust be rehearsed or material is lostFirst and last items are best recalledFirst items enter long termLast items remain in short termHowever, fast presentation prevents rehearsal, reducing memory of the firstDelaying recall prevents last info from being rememberedMaintenance rehearsal does not always ensure long term