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Psychology > 4.2 The visual system > Flashcards

4.2 The visual system Flashcards

1
Q

eyes rely on light energy

A

eyes take in light information and convert it into neural signals that the brain can interpret

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2
Q

eyes

A

tool for collecting light energy

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3
Q

light

A

travels through space in the forms of waves

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4
Q

wavelength

A

the distance b/w two waves

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5
Q

amplitude

A

range
distance b/w the lowest and highest points
high amplitude is brighter than low amplitude

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6
Q

the visual light spectrum is just a small part

A

gamma rays (too short to see ex, used for tanning)
x-rays
ultraviolet rays

visible light

infrared rays
radar
radio waves (too long for us to see)
ac circuits

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7
Q

shortest waves lengths we can see are

A

blue or purple

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8
Q

longest visible wave lengths is the colour

A

red

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9
Q

intermediate visible wave lengths are the colours

A

yellow and green

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10
Q

saturation

A

*light that consists of a mixture of different wavelengths have low saturation (faint colour)
# of wavelengths they receive from a single region in space
complex mixtures of wavelengths are perceived as white
*light waves that consists of mostly one wavelength have high saturation

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11
Q

what we perceive as colour represents the …

A

wavelengths that bounce off of objects

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12
Q

structure of the eye

A

designed to let light enter but also to direct light to the right spot of the inside of the eye

  • sclera
  • cornea
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13
Q

sclera

A

white surface of the eyes

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14
Q

cornea

A

clear part in the front of the eye
-shape of cornea helps direct light to right area of the eye by suspending the light waves toward the point that it needs to strike at the back of the eye

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15
Q

pupil

A

the dark opening part

  • after traveling through the cornea, light then travels through the pupil
  • size of pupil varies depending on how much light is available
  • in bright context pupil is smaller to reduce the amount of light that can enter
  • in dim context pupil is larger to allow more light to enter
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16
Q

iris

A

difference in pupil size depends on the iris

  • the part around the pupil that has a colour
  • it is a muscle that tightens around the pupil constricting it
  • when the muscle relaxes the pupil dilates
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17
Q

the lens

A

behind the pupil

  • the clear part that changes shape
  • bends light more or less
  • accommodation reflex
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18
Q

accommodation

A

refers to the lens changing shape to bend light that enters the eye, so that it strikes the right spot at the back of the eye

  • close objects need the lens to be more spherical because the light from those objects must be bent more significantly to bring them into focus
  • bringing far objects into focus requires the lens to be flat since light energy does not need need to be bent as much to direct them to the proper spot at the back of the eye
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19
Q

the retina

A

after passing through the lens the light will travel through the liquid contents of the eye and strike a structure at the back called the retina

  • photoreceptors
  • ganglion cells
  • optic nerve
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20
Q

photoreceptors

A

pair of light receptors designed to absorb light

  • transduce light energy into neural signals
  • rods and cones are two types of photoreceptors
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21
Q

ganglion cells

A

take signals from photoreceptors and relay that info to the brain

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22
Q

optic nerve

A

where the axons of ganglion cells get bundled together
fibres going to the brain
blind spot

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23
Q

rods

A

are more sensitive to light and they do not provide as fine-grained an image as the cones

  • they can detect light at very low intensities so we rely on them more in dim lighting
  • grey, black, white
  • yellow dots dominate outside of the fovea which represents the periphery of the visual field (not as defined as cones )
24
Q

cones

A

are less sensitive to light so we don’t rely on the as much in the dark
-different cones respond to different wavelengths, so we rely on them for colour vision
(the blue green and red dots dominate in the fovea which represents the centre of the visual field

25
Q

dark adaptation

A

the process of rods and cones adjusting their sensitivity to dark lighting conditions
this is why dark environments feel less dark as we spend more time there

26
Q

tri-chromatic (or young-Helmholtz) theory

A

colour vision depends on three types of cones that are each sensitive to different wavelengths of light that correspond to the colours blue, green and red.

27
Q

colour blindness

A

people missing one or more of the cones

28
Q

negative afterimage

A

starting at one colour and the afterimage is a different colour

29
Q

opponent-process theory

A

colour vision depends on patterns of neural signals that put pairs of colour in opposition
red vs green
blue vs yellow
black vs white
individual ganglion cells respond most vigorously to one colour (red) but their activity is inhibited when presented with the opposing colour (green),
this explains negative afterimages, cells that responds to (green) get exhausted over time when presented with something green and viewing green inhibits cells that respond to red
tired green ganglion cells cant compete with a rebound effect from the previously inhibited red ganglion cells, once we stop viewing something green. instead of a return to a neutral state, we end up experiencing an illusion of red after staring at green

30
Q

nearsightedness (or myopia)

A

prevents bringing far scenes into focus
this occurs when the eye is slightly too long
the light needs to bent less

31
Q

farsightedness (or hyperopia)

A

prevents bringing close objects into focus

  • when the eye is just a bit short that the light is not sufficiently bent by the time it strikes the retina at the proper spot
  • the light needs to bent more
32
Q

optic chiasm

A

the crossover of optic nerves at the brains midpoint
cross over for the optic nerve fibres from the right side of the brain for the left eye and the optic nerve fibres from the left side for the right eye

33
Q

left visual field is processed by the

A

right hemisphere

34
Q

right visual field is processed by the

A

left hemisphere

35
Q

on the way to the occipital cortex, visual inputs get routed through the …

A

lateral geniculate nucleus of the thalamus

36
Q

feature detection cells

A

cells in the occipital cortex of humans and other animals preferentially respond to edges presented at a specific orientation and at a specific location in the visual field

37
Q

ventral stream of visual processing

A

deals with processing visual info according to its identity (its a pencil!)

38
Q

perceptual constancies

A

info received by our eyes vary a great deal according to :
-viewing angle
-lighting conditions
-distance
we are able to unconsciously correct for these variations and perceive the properties of objects as constant or unchanging

39
Q

shape constancy

A

different viewing angles do not lead us to conclude objects are changing shape

40
Q

colour constancy

A

light and shadow change the wavelengths that bounce off of objects to strike our retinas
(amount of wavelengths in dim or bright light reflecting off the objects does not change colour)

41
Q

size constancy

A

the size of image an object projects varies with distance, but we are able to correct for this variability
closer objects project larger images than further objects

42
Q

dorsal stream of visual processing

A

deals with processing visual info for the purpose of guiding motor actions (enabling use of the pencil for writing)

43
Q

depth perception

A

despite the 2D image projected to our retinas, depth perception enables us to perceive the world in 3D

44
Q

binocular depth cues

A

-combined influence and info from both eyes
convergence
retinal disparity

45
Q

convergence

A

(extreme convergence is fully crossing our eyes)

-closer objects need more convergence (most objects we see already are close though)

46
Q

retinal disparity

A

since both of our eyes view the world from different angles we can use the difference in viewing angles to determine how far an object is away from us
(3D movies )
separate but overlapping images to each eye

47
Q

monocular depth cues

A 
-each eye separately
accommodation 
motion parallax
interposition
object brightness 
linear perspective 
texture gradient 
height in plane 
relative size
48
Q

accmmodation

A

lens changing shape in response to brining close vs far objects into focus
-source we can use to determine the distance of objects

49
Q

motion parallax

A

helps with depth perception when we are on the move
in those situations, visual inputs that are closer to us will appear to move faster and in the opposite direction we are moving, where the ones that are farther away appear to move slowly and is moving in the same direction as we are

50
Q

interposition

A

these cues conclude interposition in which one can infer that an object is closer than another one because it obscures the view of the other object

51
Q

object brightness

A

since the light received by our retinas from objects that are further away will be at lower intensity than light from closer objects

52
Q

linear perspective

A

occurs when parallel lines precede into the distance, when they do the lines appear to get closer together

53
Q

texture gradient

A

far objects will tend to be less defined and blurry then close objects

54
Q

height in plane

A

aspects of the environment that are higher in our visual field will tend to be further away

55
Q

relative size

A

an object will project a smaller image onto our retinas if it is further away from us

56
Q

the visual system

A

helps guide and helps our interactions

Psychology (42 decks)

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