Midterm Study Guide
Popular in Psychology of Perception
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This 6 page Study Guide was uploaded by Sarah Kincaid on Sunday October 16, 2016. The Study Guide belongs to 222 at Boston University taught by Rucci in Winter 2016. Since its upload, it has received 77 views. For similar materials see Psychology of Perception in Psychology at Boston University.
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Date Created: 10/16/16
Midterm Study Guide Sensation: detection of signal; external signal internal signal Perception: assigning meaning to detected signal Gustav Fechner - Father of psychophysics (science of defining quantitative relationships between physical & psychological events) - Panpsychism: all matter has consciousness - 2-point touch threshold: minimum distance two tactile stimuli can be distinguished - Absolute threshold: minimum stimulus detected 50% time - JND: just noticeable difference; smallest noticeable difference between two stimuli or the minimum change in a stimulus - 2 changes in sensation should be equal…. all JNDs must feel the same – incorrect - Fechner’s Law (logarithmic): S = k log I Weber’s Law (linear): DI = k I (does not fit all models) a Steven’s Law (power): DS = k I (appears to be accurate but not able to prove) Ways to determine threshold - Method of constant stimuli: lots of stimuli of varying ranges are presented in one sitting (long time, boring, tedious) - Method of limits: go from smallest biggest stimuli, vice versa, back and forth - Method of adjustments: least reliable; subject manually determines threshold (quick) Magnitude estimation: participant assigns value (if that’s 1/10, then this is 3/10…) Cross modality matching: participant matches sensation intensity of one modality with the intensity of another (light vs bitterness) Psychophysical theory is used in Signal Detection… - To quantify observer’s response to presented signal in presence of noise Stimulus Present Stimulus Absent Response Present Hit False Alarm Response Absent Miss Correct Rejection Pr(Hit)+Pr(Miss)=1.00 Pr(FA)+Pr(CR)=1.00 Criterion: threshold at which a stimulus is detected - High criterion, conservative: less false alarms & hits; more correct rejections & misses - Unbiased criterion: at or near the intersection of two curves - Low criterion, liberal: more hits and false alarms; less correct rejections & misses Midterm Study Guide d’= how far apart distributions for stimulus present and absent are from each other - d’=0; useless, nearly on top of each other; hard to discriminate - d’=1; moderate sensitivity; relatively easy to discriminate - d’=≥3; high sensitivity; easy to discriminate ROC curves (receiver operating characteristic curves) - graph of hit rate as function of false alarm rate - d’=z(Hits)-z(False Alarms) - linear: useless, d’=1, no discrimination - as observer sensitivity increases, curve bows to upper left corner (100% hits, 0% false alarms) Sine wave - amplitude (how tall is peak) - frequency (# of periods per unit time, usually second) - phase (position of sine wave along axis: i.e. 0, 90, 180, 270, 360) In visual system, sine components Amplitude Frequency Low Low contrast, more even Blurrier, changes slowly, distribution of luminosity general/surfaces High High contrast, larger range Sharper, edges, changes of luminosity quickly Fourier Analysis aka frequency/spectral analysis - separates signal into component sine waves at different frequencies - all signals represented by sum of sinusoidal functions - all signals represented by 2 graphs (amplitude as function of frequency, phase as function of frequency) 360 degrees = 2π radians Signals are sent through neurons via action potentials (series of events that lead to a signal travelling along axon (Na+ depolarizes)) - axon, axon terminal (presynaptic), synaptic vesicles (pushed by Ca2+), synapse with dendrites Neurotransmitter: chemical substance used in neuronal communication at synapses - Glutamate: excitatory synapses all over the brain; used at most “modifiable” synapses (capable of increasing/decreasing in strength) o “modifiable” synapses are possibly main memory-storage elements - GABA: inhibitory synapses all over brain; sedative/tranquilizing drugs are GABA enhancers (glycine = inhibitory transmitter in spinal cord) - Acetylcholine: neuromuscular junction connecting motor nerves to muscles (curare, which causes paralysis, blocks transmission at these synapses) Midterm Study Guide - Dopamine: reward system; degeneration causes Parkinson’s Disease & schizophrenia - Serotonin: monoamine neurotransmitter; most produced & found in intestine, 90% (remained in CNS* neurons); appetite, sleep, memory and learning, temperature, mood, behavior, muscle contraction, and function of the cardiovascular system and endocrine system; possibly involved with depression - Substance P: undecapeptide responsible from pain transmission from certain sensory neurons to CNS* EEG (electroencephalography) - Weak signals (from electric fields imposed) are received by electrodes on skull by providing different signals & seeing patterns in + and – oscillations (+ voltage down, - up on EEG graphs) - Event-related potentials: averages of many trials timed with the stimulus (stimulus at t = 0), need at least 100 repetitions - Good temporal resolution & poor spatial resolution - Cheap MEG (magnoencephalography) - Good temporal resolution & better spatial resolution - Measures change in magnetic fields across neurons - Magnetic field formed in head by small magnetic field around the stimulated neurons - Expensive CT (computerized tomography) - X-rays create slices through volumes of material MRI (magnetic resonance imaging) - Show soft tissue, unlike CT - Atomic response to strong magnetic fields to form images of brain structures (magnetic dipoles release energy) - loud fMRI (functional magnetic resonance imaging) - Measure localized areas in brain bc activated neurons = increased blood flow = measure changes in oxygenated & deoxygenated blood to strong magnetic fields - Blood oxygen level-dependent signal (BOLD) o Oxygenated: deoxygenated hemoglobin permits localization of brain neurons involved in task (need more oxygen to work) - Time consuming, must stay still - Good spatial but poor temporal resolution (bc averaging) - Stronger magnetic field = better spatial resolution PET (positron emission tomography) Midterm Study Guide - Define locations of high neural activity in brain via metabolism of brain cells (radioactive isotope) - Quiet Sensation matters which neurons are stimulated not how they are stimulated. Cranial nerves involved in vision: 1. Optic (I) nerve 2. Oculomotor (III) nerve 3. Trochlear (IV) nerve 4. Abducen (VI) nerve 5. What is light? - A wave - a stream of photons - tiny particles, one quantum of energy each - human eyes only sensitive to visible light, 430-770 nm - travels quickly (much faster than sound) Electromagnetic spectrum (e.g. infrared – warmth, radio waves – sound) - higher energy = higher frequency = shorter wavelength - lower energy = lower frequency = longer wavelength - Period (T) = wavelength (λ) - Frequency (F) is inversely proportional to wavelength/period o F = 1/T = 1/period = 1/λ = 1/wavelength Historically, how has light been measured/attempted to be measured? - Galileo: lit lanterns on two different hills – didn’t work, too short a distance - Ole Roemer: used Jupiter’s moon, Io, to measure how quickly moon’s light travelled to Jupiter from different distances What light can do as it interacts with objects - Absorbed: takes up energy – not transmitted - Scattered: disperses energy in irregular fashion - Reflected: redirects energy when it strikes a surface (sometimes back to origin) - Transmitted: passes energy on through a surface (neither reflected nor absorbed by surface) - Refracted: alters energy as it passes through another medium in which it has a different speed – changes its course (light through air then water seems “bent”) Pathway of light Cornea Aqueous humor pupil lens vitreous humor retina optic nerve brain occipital lobe Eye anatomy Midterm Study Guide - Cornea: transparent window to eye that refracts light; consists of highly ordered fibers, nerves endings and no blood vessels; delicate/rapid healing; responsible for tear production - Aqueous (water) humor: refracts light (change in medium); watery liquid in anterior chamber – provides nutrients for cornea & lens - Iris/pupil: pupillary light reflex (regulates amount of light entering eye); pupil is opening in center of iris - (Crystalline) Lens: changes shape to adapt focus - Vitreous humor: transparent liquid in vitreous chamber (80% volume); floaters - Retina: light sensitive membrane at back of eye with rods and cones; records image; entry point of visual system; light comes from back of eye (fundus) up through bipolar & ganglion cells to photoreceptors and eventually to optic nerve to go to brain o Rods: night vision; low lighting; no color processing o Cones: day vision; finer acuity; color processing; lots of light Why have both? To be better suited to different environments (duplex retina in humans) Refraction: cornea and lens focus light rays Accommodation: lens changes shape to tune refraction (how much bend light ray) for the distance so that it is in focus - Ciliary muscles with strings, Zonules of Zinn, which are connected to the floating lens o For near images, muscle contracts & strings loosen so lens is thicker o For far images, muscle relaxes & strings are taut so lens is thinner - Diopter: unit of refractive power reciprocal to focal length (in m) o Diopter = 1/distance Emmetropia: no refractive error – rays converge at same point Myopia: nearsightedness; light is focused in front of retina; eye is too long so rays intersect (blurry images in distance) Hyperopia: farsightedness; light focused behind retina bc eye too short; different strength lenses to correct Astigmatism: unequal curving of one or more refractive surfaces in eye (usually cornea) causes visual defect Presbyopia: natural aging, muscle contracts still but lens is hard, which makes it harder for lens to change shape (close objects are suddenly blurry); first noticeable in dark area Cataracts: opacity of lens (irregularly packed crystallins) which absorbs & scatters light (less light retina = blurry image); lens should be transparent (i.e. regularly packed crystallins); - Congenital cataracts: present at birth; affect visual development if not corrected Retinal cells Midterm Study Guide - Bipolar cells: contacts bipolar, ganglion, and other amacrine cells - Ganglion cells: photoreceptor info from 2 intermediate neurons, bipolar and amacrine cells - Horizontal cells: contacts photoreceptor and bipolar cells Photo activation - Biochemical cascade of events leading to glutamate concentration change for rods & cones (same process for both, just different photons dif pigments) - Photon absorbed by visual pigment which changes shape - Na+ channels close & cell hyperpolarizes (more negative than surrounding potential) - Less glutamate released at synaptic terminal (graded potentials) when a photon is captured (less neuromotivators sent) o This means more activity in the dark - The following bipolar cell will become hyperpolarized/depolarized depending on its type Adjusting to light and dark… - pupil is bigger in dark so lens must work well for objects to be in focus - in the bright, the pupil is tiny so images are focused
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