Vision Flashcards

0
Q

Fovea

A

Cones only At the retina’s periphery, only rods

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1
Q

Parts of the eye (front to back)

A

Cornea, pupil/iris, lens, retina (fovea, blind spot)

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2
Q

Connection between sensorireceptors and retinal ganglion cells

A

Rods and cones connect with bipolar neurons Bipolar neurons connect to ganglion cells Ganglion cells group together to form optic nerve

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3
Q

Convergence in the retina

A

Cones converge less, more likely to have one-to-one connection through bipolar to ganglion cell: greater acuity Rods have higher convergence: better sensitivity to to light but lessened visual acuity

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4
Q

Visual field as it corresponds to retina

A

Right side of each eye’s visual field forms left half of each eye’s retina; left side of visual field forms on right half of each eye’s retina

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5
Q

Pathway from Visual Field to Cortex

A

Visual field –> retina –> optic nerve (crossover occurs) –> nasal fibers from left eye go to right hemisphere and nasal fibers from right eye go to left hemisphere, however temporal side fibers do not cross over (all left visual field info ends up in right hemisphere and all right visual field info ends up in left hemisphere) –> LGN (lateral geniculate nucleus of thalamus) –> visual cortex, association areas, & superior colliculus

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6
Q

Hubel and Wiesel found neural basis for…

A

Feature detection theory: certain cells are maximally sensitive to certain features of stimuli Simple, complex, and hypercomplex

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7
Q

“Simple cells” in visual cortex

A

give information about orientation and boundaries of a visual object

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8
Q

“Complex cells” in visual cortex

A

respond to more advanced information about orientation, such as movement

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9
Q

“Hypercomplex cells” in visual cortex

A

Give information about more abstract concepts, like object shape

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10
Q

Hubel and Wiesel (methodology)

A

single-cell recording; recording from single nerve fibers Place microeletrode in cortex so sensitive it records activity of single cell

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11
Q

Illumination vs. Brightness

A

Illumination: physical measurement of amount of light Brightness: subjective experience of light intensity

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12
Q

Adaptation

A

Adapt to darker environment: dark adaptation Adapt to brighter environment: light adaptation

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13
Q

Rhodopsin

A

Photochemical/photopigment used by rods; Made of retinal (vitamin A derivative) and opsin (a protein)

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14
Q

Rhodopsin function

A

When rhodopsin absorbs photon of light, pigment decomposes into retinal and opsin: “bleaching” Dark adaptation is the time is takes for rhodopsin to regenerate after bleaching Vitamin A deficiency –> difficulty seeing in the dark

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15
Q

Simultaneous brightness contrast

A

A target area of a particular luminance appears brighter when surrounded by a darker stimulus than when surrounded by a lighter stimulus

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16
Q

Lateral inhibition

A

Adjacent retinal cells inhibit one another causing simultaneous brightness contrast. If a cell is excited, neighboring cells are inhibited. Creates contrast; sharpen and highlights the borders between dark and light areas

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17
Q

Wavelength of light

A

Color perception. Humans: 400 to 800 nm

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18
Q

Subtractive color mixture

A

Occurs when we mix pigments. (Ex. Blue + yellow = green)

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19
Q

Additive color mixing

A

Has to do with lights. Primary colors with additive mixing are red, blue, and green.

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20
Q

Young-Hemholtz theory

A

Trichromatic theory. Suggests that the retina contains three different types of cones which are differentially sensitive to different colors: red, green, blue. Combine stimulation of these receptors produces all color. Young demonstrated that by mixing the three primary lights, all other colors of the spectrum can be produced

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21
Q

Ewald Hering & Opponent-Process Theory of Color

A

Criticized the trichromatic theory of color vision; held that yellow must be one of the primary colors, and yellow was a basic color along with red, blue, and green. Organized in opposing hair cells: red would excite a red-green cell and green would inhibit the red-green cell. (Hence, you can’t see reddish-green). Also included an opposing parent to code brightness (something like black-white).

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22
Q

Modern research in color processing

A

Supports Helmholtz’s theory. Are indeed three types of cones, each one maximally sensitive to a different primary color. However, cells in LGN of thalamus may apply a system similar to the opponent-process theory

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23
Q

Afterimages

A

This concept led Hering to his theory. The visual perception that appears after prolonged or intense exposure to a stimulus.

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24
Q

George Berkeley, 1709

A

Listed various cues for depth perception

25
Q

Interposition (overlap)

A

Refers to the cue for death perception when one object covers or overlaps another object. We see object A as being in front.

26
Q

Relative size

A

Can judge distance by comparing the size of images you perceive with what you know about their actual size

27
Q

Linear perspective

A

Refers to the convergence of parallel lines in the distance.

28
Q

Cues for depth perception

A

Interposition, relative size, linear perspective, texture gradients, motion parallax, binocular disparity (only binocular cue, all others were monocular)

29
Q

Texture gradients (J. J. Gibson)

A

Changes in texture gradient can indicate surfaces receding in depth (as distance increases) or may indicate a corner. For example: hardwood getting narrower as it gets further away (horizontally; different from linear perspective) or the way tile pattern changes, indicating a corner.

30
Q

Motion parallax

A

Phenomenon where… When in motion (as in a car/train), when fixated on an object halfway between you and the horizon, objects closer to you and your fixation point appear to move the same direction you do. The perceived speed at which these objects appear to move also varies depending on how close the object is to your fixation point.

31
Q

Kinetic depth effect

A

Specific type of motion parallax. Object is moving rather than the observer. The motion of that object gives us cues about the relative depth of the parts of the object.

32
Q

Binocular disparity

A

Also called stereopsis. Cue depending on the fact that the distance between the eyes provides us with two slightly disparate views of the world.

33
Q

Binocular parallax

A

The degree of disparity in the retinal images of the eyes due to the slight differences in the horizontal position of each eye

34
Q

Perceptual objects

A

Use perception of form cue including consideration of figure and ground

35
Q

Gestalt laws explaining organization of visual information

A

Proximity, similarity, good continuation, closure, prägnanz

36
Q

Law of proximity

A

Elements close together tend to be perceived as a unit

37
Q

Law of similarity

A

Objects that are similar tend to be grouped together

38
Q

Law of good continuation

A

Elements that appear to follow in the same direction tend to be grouped together (ex. Break down overlay of two lines as their most simple versions)

39
Q

Subjective contours

A

Perception of contours which are not physically present. Law of closure: when a space is enclosed by a contour, it tends to be perceived as a figure

40
Q

Law of prägnanz

A

Encompasses all the other Gestalt laws of organization. States that perceptual organization will always be as regular, simple, and symmetric as possible.

41
Q

Five ways for light to appear to be moving

A

Real motion, apparent motion (stroboscopic movement/phi phenomenon), induced motion, autokinetic effect, motion aftereffect (waterfall illusion)

42
Q

Real motion

A

Light which is actually moving and appears to be moving

43
Q

Apparent motion

A

An illusion that occurs when two dots flashed in different locations on a screen seconds apart are perceived as one moving dot of light

44
Q

Induced motion

A

The illusion of movement occurring when everything around the spot of light is moved (when the background moves)

45
Q

Autokinetic effect

A

An illusion that occurs when a spot of light appears to move erratically in a dark room simply because there is no frame of reference

46
Q

Motion aftereffect

A

Occurs when you first view a moving pattern (such as stripes moving off to the right) and then you view a spot of light, the spot off light will appear to move in the opposite direction

47
Q

Proximal vs. distal stimuli

A

Distal: actual object or event out there in the world Proximal: the information our sensory receptors receive about the object

48
Q

Four constancies of visual perception

A

Size constancy, shape constancy, lightness constancy, color constancy

49
Q

Wolfgang Kohler

A

Introduced theory of isomorphism: suggests there is a one-to-one correspondence between the object in the perceptual field and the pattern of stimulation in the brain. Addresses how figure-ground configurations are represented in the brain. Has not fared well empirically.

50
Q

Two types of psychological processing in visual system (directional)

A

Bottom-up processing: refers to object perception that responds directly to visual input (data-driven processing) Top-down processing: refers to object perception guided by conceptual processes such as memories and expectations that allow the brain to recognize the whole object and then the components (conceptually driven processing) Modern theories of object recognition assume both.

51
Q

Size constancy

A

When an object appears to remain the same in size despite the fact that it’s image on the retina has changed in size (perceive the change in retinal size as distance)

52
Q

Emmert’s law

A

Relates size constancy and apparent distance Led to size-distance invariance principle, which states size constancy depends on apparent distance

53
Q

Ames room

A

Fools observer into believing person A & B appear to be at same distance so observer perceives equally sized people as different sizes because of lacking information on distance (difference in visual angles is not attributed to distance but size)

54
Q

Moon illusion

A

Moon on the horizon appears larger than moon at its zenith (despite the fact that both moons are the same size, in actuality and on the retina) One explanation is distance cues like buildings causes moon on horizon to appear bigger

55
Q

Shape constancy

A

Retinal shape does not necessarily match perceived shape (example an open door) We use information like depth cues to perceptually resolve the shape

56
Q

Lightness constancy

A

Refers to the fact that, despite changes in the amount of I light falling on an object (illumination), the apparent lightness of the object remains unchanged. Occurs because levels of illumination are the same for both the object and the background

57
Q

Color constancy

A

Tendency for the perceived color of an object to remain constant despite changes in the spectrum of light falling on it.

58
Q

Visual perception research in infants

A

Preferential looking (measure time spent looking at two stimuli; difference in time infers that the infant can discriminate between the two stimuli) Habituation (when new stimulus is presented, if the infant can discriminate between the old and new, he/she will orient toward it)

59
Q

Infant visuals

A

Can follow object/light with their eyes when it’s placed in the center of their visual field. Can perceive color, simple figures, sharp contrast, and can see in dim light.

60
Q

Visual cliff

A

Glass on table creates “visual cliff”; developed by Gibson and Walk As young as 6 months, infant will not cross the cliff, indicating their ability to perceive depth

61
Q
A