PSYCH100H EXAM 2 NATIVISM some knowledge is innate EMPIRICISM some knowledge acquired through experimental learning Distal stimulus how object actually appears Proximal stimulus physical stimulation available to be measured The distal stimulus is inferred based on info from proximal stimulus Psychophysics the study of relationships btw the distal stimulus and our sensations Leads to measurements of presumed sensations determinations of thresholds Perceptions are generated by combining traditional sensory psych Absolute Threshold minimum stimulus energy needed for detection 50 of the time Difference Threshold Just Noticeable Difference change of a stimulus needed for detection 50 of the time The JND is a constant fraction of a standard I I Weber s Law Fechner s Law says that stimulus strength perceived stimulus strength display a logarithmic relationship Equal increases in stimulus magnitude yield exponentially lower growth rates of sensation Signal Detection Theory Experiments are impacted by response biases must distinguish btw hits misses false alarms Hit correct identification of the signal Miss no identification of signal False Alarm incorrect identification of signal More guessing more of BOTH hits and false alarms Receiver Operator Curve plots false alarms vs hits at diff stimulus intensities while manipulating response bias For hits ABOVE threshold there is a greater hit rate For hits BELOW threshold there is a greater false alarm rate Transduction 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 neurons Across Fiber Pattern Theory overall pattern activation in a set of nerve fibers codes sensory qualities ex olfactory system VISION AND LIGHT Visible light only a small part of the electromagnetic spectrum Encompasses large fraction of energy reaching earth s surface Wavelength corresponds to color light intensity corresponds to brightness Light is focused by a convergent lens Principal axis line that runs through center of curve Principal focus where rays converge Forms images by refractive properties As object gets closer image enlarges moves farther from focal plane Image cannot be formed if object is at focal distance Cornea lens focus light on the retina Neural tissue at back of eye makeup optic nerve Accomodation occurs when the lens BULGES to focus NEAR objects FLATTENS for FAR objects Refractive errors impair perceptions of distance Myopia concave lens correction Farsighted convex lens correction Rods contain rhodopsin Function in low levels of light Cones contain photopsins Function during daylight Contained in the fovea highest density of photoreceptors Rods cones differ in time course of dark adaption max sensitivity Rods cones are connected with bipolar and ganglion cells Ganglion cells receive both excitatory and inhibitory input edge enhancement Lateral inhibition ability of an excited neuron to reduce the activity of its neighbors LATERAL relationships COLOR VISION Tri chromatic Theory Helmholz color vision is generated by 3 wavelength sensitive receptors Does not account for uniqueness of yellow color blindness or afterimages Hering proposed 3 visual opponent process channels Red green Blue yellow Black white Each photoreceptor responds to a range of wavelengths Wavelength corresponds to pattern of photoreceptor responses Existence of several types of opponent process ganglion cells All cones rods have strong response White light Red light Green light Blue light Yellow Light Red strong response green medium response blue weak response rods weak response Red medium response green strong response blue med response rods med Red weak response green medium response blue strong response rods weak Red strong response green strong response blue med response rods strong response Yellow color is created by adding middle long wavelengths summation to same bipolar cells Color Weakness Blindness Genes for L and M opsins red and green are both on x chrom Gene for S opsin blue is autosomal Extra gene copies do not impair color vision PERCEPTION Empiricists Locke believe perception associations btw simple sensations Nativists Kant believe perception is guided by a priori mental processes Nativism 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 cues Binocular Disparity difference btw two retinal images decreases when farther Interposition monocular cue spatial inferences Retinal image is flat Requires either learned or unlearned INFERENCE of depth Texture gradient density increases as objects move farther away Size of retinal image increases when closer size of objects allow distance inferences Gestalt Psychology Pattern Innate mental processes organize stimuli into patterns Law of Pragnanz perception favors symmetry and simplicity Believe that we innately separate figure and background in perception Reification 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 innateness Continuity patterns in sensory persist in the mind Common fate elements moving in same direction together are perceived as a unit Invariance common objects retain their shapes when moving or rotating Good continuation simplest interpretation is made Closure assumption of filling the gap to create a shape MEMORY Implicit memories we access w out being consciously aware of doing so motor skills Explicit memories we re consciously aware of accessing episodic semantic spatial generic involves both short and long term memory Encoding the form info is placed in during learning Storage the record made of this info in the brain Retrieval of this info is studied by recall or recognition Short term memory temporary Capacity is about 2 7 items Must be rehearsed or material is lost First and last items are best recalled First items enter long term Last items remain in short term However fast presentation prevents rehearsal reducing memory of the first Delaying recall prevents last info from being remembered Maintenance rehearsal does not always ensure long term storage The more elaborately items are encoded the more likely they are to be recalled later Forgetting is a