sens1

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ralissa
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64527
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sens1
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2011-02-06 18:37:30
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Sensation & Perception Exam 1
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  1. Sensation
    the initial process of detecting and encoding environmental energy
  2. Perception
    the process of organizing and interpreting sensations into meaningful experiences
  3. Doctrine of Specific Nerve Energies
    the quality of a sensation elicited by a stimulus depends primarily on the nerve stimulated and only secondarily on the stimulus itself
  4. Synesthesia
    condition in which stimulation of one sense evokes an involuntary experience in another sense
  5. Psychophysics
    the study of the relationship between the physical properties of a stimulus and the subject's experience of the stimulus
  6. Absolute Threshold
    smallest amount of energy necessary for an observer to reliably detect a stimulus
  7. D Prime
    a measure of how sensitive a subject is to a stimulus in a Signal Detection Theory (SDT) experiment
  8. Receptive Field
    the region on the receptor surface that, when stimulated, influences the firing rate of the cell
  9. Contribution of Plato
    • Emanation Theory
    • an inner fire sends out rays through the eyes that bring back information about the world
  10. Contribution of Alhazen
    • Eye works like pinhole camera
    • Eye pupil is much too large to work this way
    • Alhazen thought he was wrong because pinhole camera image is upside down but this refutation of his own theory is also wrong; our eye does create an upside down image on our retina
  11. Contribution of Kepler
    • demonstrated that eye uses lenses to create an image
    • cut back off of cat's eye and used it as projector
  12. Contribution of Mueller
    • developed Doctrine of Specific Nerve Energies
    • suggested, incorrectly, that mechanical stimulation of the optic nerve is what produces image (it is actually chemical reaction)
  13. Contribution of Weber (veber)
    • Founder of psychophysics
    • First to study the Difference Threshold
  14. Contribution of Fechner
    • developed 3 methods for determining Absolute Threshold
    • Magnitude Scaling - determining relationship between perceived magnitude and stimulus intensity
  15. Contribution of Stevens
    Developed most accurate law of magnitude scaling
  16. Weber's Law
    • /\I / I = k
    • I = magnitude of original stimulus
    • /\I = increment in intensity that can just be discriminated from I
    • k = constant depending on the sense being measured
  17. Fechner's Law
    • p = k[log(I)]
    • p = perceived magnitude
    • k = constant depending on sense being measured
    • I = stimulus intensity
  18. Stevens' Law
    • p=kI^b
    • p = perceived magnitude
    • k = constant depending on sense being measured
    • b = constant depending on sense being measured
    • I = stimulus intensity
  19. Fechner's 3 Methods for Determining Absolute Threshold
    • Method of Constant Stimuli - number of stimulus intensities selected beforehand, stimuli presented numerous times in random order and subject reports whether each stimulus is detected, graph plotted showing detection and intensity, point at which stimulus detected 50% of time is absolute threshold
    • Method of Limits - researcher starts with stimulus clearly above threshold, adjusts stimulus intensity down in fixed increment until subject cannot detect, repeated several times sometimes ascending sometimes descending, average of crossover points is absolute threshold
    • Method of Adjustment - intensity of stimulus is adjusted by observer until they can barely detect it
  20. Problems with Fechner's Methods
    • Observer's criteria for responding greatly affects results
    • Observer could be lying
  21. Assumptions of Fechner's Law
    • Weber's law is correct
    • All JND's are subjectively equal
  22. Steven's Magnitude Estimation Experiments
    • Subjects presented with stimulus and given arbitrary number distinguishing its intensity (shown light with brightness of "10")
    • Stimuli of various intensities presented to subject and subject assigns number to each, relative to standard (shown brighter light and responds with "30")
    • Reported number is perceived intensity; actual measure (wattage, pounds, etc.) is stimulus intensity
  23. Significance of "b"
    • b<1 - doubling of stimulus intensity leads to less than doubling of perceived magnitude
    • b=1 - doubling of stimulus intensity leads to doubling of perceived magnitude
    • b>1 - doubling of stimulus intensity leads to more than doubling of perceived magnitude
  24. Why is signal detection theory superior to Fechner's methods for determining absolute threshold?
    It eliminates the possibility for subjects to be lying and measures a subject's sensitivity independent of their response bias.
  25. Signal Detection Theory Experiment
    • On each trial, subject is presented with either very faint stimulus or no stimulus.
    • Subject reports whether or not the stimulus was present.
    • Sequence is repeated many times.
  26. Hit
    • Subject's response - stimulus present
    • Actual state - stimulus present
  27. Miss
    • Subject's response - stimulus absent
    • Actual state - stimulus present
  28. False Alarm
    • Subject's response - stimulus present
    • Actual state - stimulus absent
  29. Correct Rejection
    • Subject's response - stimulus absent
    • Actual state - stimulus absent
  30. Four Main Parts of Neuron
    • Dendrites - receive information from presynaptic neuron
    • Soma - cell body
    • Axon - site of action potential, transports electrical impulse to terminal buttons
    • Terminal buttons - send information to postsynaptic neuron
  31. Resting Potential
    -70
  32. Absolute Refractory Period
    the brief period in which a neuron cannot fire again after generating an action potential
  33. Relative Refractory Period
    the brief period in which a neuron is less likely to fire again after generating an action potential
  34. How do neurons indicate their level of excitation?
    Their rate of fire
  35. What is the significance of Werner and Mountcastle's 1965 experiment?
    Showed that perceived magnitude is due to firing rate of sensory neurons.
  36. Why do we have two eyes?
    • Enhanced depth perception
    • Increased peripheral vision
    • Enhanced vision in dark or dim light
    • One eye covers the other's blind spot
    • Spare
  37. Function of Eyebrows
    Keep sweat out of our eyes
  38. Function of Cornea
    primary refractive surface of the eye
  39. Function of Iris
    • Controls amount of light entering eye
    • Absorbs light
  40. Function of Lens
    allows adjustments in focus of eyes
  41. Lens System
    • Bends light rays to focus many on single spot on retina
    • Advantage - creates bright image
    • Disadvantage - can be out of focus
  42. Pinhole Camera
    • uses very small hole to let in one light particle for each spot in space
    • Advantage - no focusing problems
    • Disadvantage - image is very dim
  43. Myopia
    • eye is too long
    • creates near-sightedness
  44. Hypermetropia
    • eye is too short
    • creates far-sightedness
  45. Similarities of Rods and Cones
    • Contain light-sensitive chemicals called photopigments
    • Hyperpolarize in response to light (resting potential is -30 and this decreases when exposed to light)
    • Do not have action potentials
    • Synapse with bipolar cells
    • At BACK of retina
  46. Differnces Between Rods and Cones
    • Rods are more sensitive to light than cones
    • Rod are larger than cones
    • There are many more rods than cones (120M/6M)
    • Rods' pigment is not as sensitive to wavelenght as cones (this is why cones detect color)
    • Rods are found only in the periphery, but Cones are concentrated in Fovea
    • Rods' pigment reginerates in 30 min, Cones' pigment reginerates in 6 min.
  47. Function of Bipolar Cells
    carry output of photoreceptors to ganglion cells
  48. Function of Horizontal Cells
    • Modulate connection between photoreceptors and bipolar cells
    • Allow photoreceptors to communicate with eachother
  49. Function of Amacrine Cells
    Modulate connection between bipolar cells and ganglion cells
  50. Function of Ganglion Cells
    generate the action potentials that are carried to the brain
  51. Why is center-surround organization desirable in ganglion cells?
    Edge enhancement
  52. Three Types of Ganglia
    • P cells (parvo) - color and form perception, center-surround
    • M cells (magno) - motion perception, depth perception, simple detection of light, center-surround
    • K cells (dust) - code overall level of illumination, no center-surround

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