Exam #3

Monday, November 17th, 2025

What are three functions of color vision?

helps us classify and identify colors (red = stop, anger)

facilitates perceptual organization (seeing one object from another)

allows us to survive (recognizing the colors of food)

What did Issac Newton propose regarding white light?

white light is a mixuture of many colors

What is a prism?

an object that could separate the different colors from white light

What is the visual spectrum?

color that humans can perceive

How many nanometers can people see color?

400 - 700

What is the wavelength for blue?

short wavelength

What is the wavelength for green?

medium wavelength

What is the wavelength for yellow?

medium/long wavelength

What is the wavelength for red?

long wavelength 

How do wavelengths get processed?

by reflecting light into the eyes, colors of objects are then determined by wavelengths

What are chromatic colors?

light is able to reflect different wavelengths (eg. red, green, blue)

What is selective reflection?

some colors reflect more than others

What are achromatic colors?

light reflects equal wavelengths (eg. white, black, gray)

What is selective transmission?

transparent objects, such as liquids, plastics and glass that allow wavelengths to pass through 

What is the use of the reflectance and transmission curves?

used to plot the percentage of light reflected or transmitted to perceive specific wavelengths

What two ways can we mix color to describe different wavelengths?

mixing paints and mixing lights

What happens when you mix paint colors?

paint absorbs or takes away colors. short, medium, and long wavelengths mix together to create black. this means it is a subtractive color mixture

blue (short) + yellow (long) = green (medium), blue and yellow no longer present

What happens when you mix light colors?

light of short, medium, and long wavelengths are superimposed (placed over eachother) they reflect white light, light produces an additive color mixture when two different wavelengths come together to create a new color

green (medium) + red (long) = yellow (medium + long)

What is hue?

the color being assessed

What is saturation?

percevived intensity and pureness of color

What is desaturation?

the fading of a color due to more white in it

What is value/lightness?

perceived brightness of the color

What is the trichromatic theory of color vision?

three different receptor mechanisms are responsible for color vision

What is the color matching experiment?

a participant had to adjust three wavelengths in a comparison field to match a test field of one wavelength

What was a test field in the color matching experiment?

the color light the experimenter wants the observer to match

What was the comparison field in the color matching experiment?

the observer must manipulate the lighting to match the test field of color

What are the key findsings of the color matching experiment?

adjusting three wavelengths allowed it to be possible to match any colors of the test field, while adjusting two wavelengths could not match all colors

What was the conclusion of the color matching experiment?

normal color vision relies on three wavelengths 

What are the wavelengths the cones consist of?

short, medium, and long wavelengths

What is the visual pigment molecule?

when the retinal bends from the opsin to produce light

What does the opsin represent?

a protein structure that differes, representing the three different pigments

What is metamerism?

a situation in which colors at different wavelengths create an identical color

What are metamers?

different wavelengths that come together to make a similar color

What happens when you only have one visual pigment receptor?

wavelengths cannot be identified, color from light looks the same (shades of gray)

What is the principle of univariance?

receptors cannot detect differences in wavelengths, only the intensity of light 

What happens when you have two visual pigment receptors?

ability to identify two wavelengths and not just the intesity of light

What happens when you have three visual pigment receptors?

ability to identify three wavelengths, creating the perception of many colors

What theory did Helmholtz, Young, and mexwell propose?

Trichromatic Theory of Color Vision

What theory did Hering propose?

Opponent Process Theory

What is the phenomenological method?

describing an observation, people observed a circle color and identified changes of a hue

What did Hering find based on his color circle experiment?

showed that differences in colors were observed as primary colors that are added in small amounts. red, yellow, green, and blue were primary colors or unique hues (pure colors that cannot be mixed with other colors).

What was Hering’s conclusion based on his Opponent Process Theory?

certain pairs of colors are opposites and do not mix

Based on phsiological evidence of the opponent-process, what are opponent neurons and where are they located?

colors that do not mix (blue/yellow, gree/red, and black/white) represent opponent neurons. opponent neurons respond to an excitatory manner to the end of the visible spectrum and an inhibitory manner to the other end for color pairings

How do the trichromatic and opponent-process theories work together?

each theory describes physiological mechanism in the visual system

trichirmatic theory explains cones in the retina

opponenent process theory explains neural response from cones to the brain

What is color deficiency? 

the partial loss of color perception 

What is color blindness?

when a person cannot see color at all, just white, gray, and black

What are Ishihara plates?

a color vision test to diagnose people with color defiencies

What are unilateral dichromats?

people with trichromatic vision in one eye and dichromatic vision in the other

What is a monochromat?

a person who has one wavelength to see color, they only see shades of gray.

it is a rare hereditary condition of color blindness, where only rods function and therefore the person is senstitive to bright light

What is a dichromat?

someone with two wavelengths to see color they can perceive some color but not all (color deficient)

Who is more likely to be a dichromat, males of females?

males are more likely because they lack an extra X chromosome. if you only have 1 X and if has a genetic defect, color becomes deficient. females have 2 X’s preventing them from being color deficient, since you only need 1 X for normal color vision 

What are the three types of dichromats?

protonopia

deutropia 

tritanopia

What is protonopia?

lacking red cones (long wavelengths)

the person sees short wavelengths (blue) and long wavelengths (yellow)

the person has difficulty seeing green and red (lacks long wavelength pigments)

What is deuternopia?

lacking green cones (medium wavelengths)

the person sees short wavelengths (blue) and long wavelengths (yellow)

the person has difficulty seeing green (lacks medium wavelength pigments) and red (cannot see red as much)

What is tritanopia?

lacking blue cones (short wavelengths)

very rare dichromat

the person sees long wavelengths (red)

difficulty seeing blue (lacks short wavelength pigment) and cannot see yellow

What is color constancy?

we perceive the colors of objects as not changing even under different lighting. prolonged exposure to a chromatic color leads to receptors in the cones to adapt to that color, making us less sensitive to that color and more senstivie to other colors not exposed as much

What is an explanation for the blue/black or yellow/white dress?

how you see color from the dress can be influenced by the illumination of light (type of light reflecting on the object. researchers are still trying to figure out why people interpret the dress differently 

What is lightness constancy?

we perceive achromatic colors (white, gray, black) as remaining relatively constant. although we may see different shades of gray (lightness) due to the amount of light reflected from the object to our eyes, the color itself does not actually change

What is depth derception?

automatic through repeated exposure of cues

What is oculomotor cue of signal depth?

cues given based on sensing the position of the eyes through tension in every muscle

What is monocular cue of signal depth?

cues available in one eye

What is binocular cue of signal depth?

cues that depend on two eyes

How are oculmotor cues created?

convergence and accomodation

What is convergence?

inward movement of the eyes when focusing on nearby object

What is accommodation?

change in the shape of the lens to focus on objects at different distances

lens flatten = far away objects

lens thickens = nearby objects

Monocular cues consist of what two types of cues?

pictorial cues and motion produced/movement-based cues

What are pictorial cues?

sources of depth info that come from 2D images from one eye

What is occlusion?

occurs when one object hides or partially hides from another object, causing the hidden object to seem far away. doesn’t tell us exactly how distant it is; all we know is that the covered object is further away

What is relative height?

objects closer to the base of the horizon are seen as more distant, whereas objects away from the base are seen as closer

What is relative size?

when objects are of equal size, the one further away takes up less of your field of view than the closer one

What is familiar size?

judging distance according to prior knowledge of the sizes of objects

What is perspective convergence?

parallel lines appear to come together in the distance, showing an increase in distance

What is atmospheric perspective?

occurs when distant objects appear less sharp (eg being very foggy and unclear than nearer objects) farther distances tend to give off short wavelengths from light. this is why the sky looks blue

What is texture gradient?

elements in a scene are seen more closely packed when the distance increases and smaller textures appear in the distance

What are shadows?

a decrease in light intensity due to blockage of light can provide info for locations, can also make objects 3D

What are the two movement-based (moetion produced) cues?

motion parallax and delection/accretion

What is motion parallax?

close objects in the direction of movement glide rapidly past but objects in the distance appear to move slowly

What is deletion?

the covering of an object

What is accreation?

the unconvering of an object

What is stereoscopic depth perception?

our awareness of depth through input by both eyes, each eye has a different viewpoint

What is a 2D image?

both eyes receive the same info

images are flat, relying on monocular cues (pictorial cues) for both eyes

What is a 3D image?

both eyes receive different info

images are positioned in different viewpoints to produce a 3D perspective

What is strabismus?

misalignment of the eyes, they rely on monocular cues instead of binocular cues

How do people with strabismus perceive images?

one eye is suppressed, causing an indivudal to see one eye to avoid double vision

What is biocular disparity?

points on the retina where an image overlaps falls on the fovea

What are corresponding retinal points?

objects that overlap into a single image

What is the horopter?

an imaginary sphere that passes through the point of focus

What are noncorresponding retinal points?

objects that do not fall on the horiopter, these points create different images in both eyes

What is absolute disparity?

objects deviate from falling on corresponding retinal points

What are angles of disparity?

the amount of absolute disparity indicates how far an object is from the horopter

What is relative disparity?

the difference between the absolute disparity of two objects

What is crossed disparity?

when you focus your horopter from a faraway object (Julie) to a close object (Bill) in front of you, the close object goes between the focused object of the horopter

What is uncrossed disparity?

when you focus your horopter from a close object (Bill) your far object (Julie) goes to the sides of your close object from the horopter 

What is stereopsis?

the ability to perceive depth through binocular disparity (differences in viewpoint for both eyes)

How is stereopsis created in movies?

slightly different positions of an image in the left eye and right eye are superimposed (placed over each other) on a screen

How does the visual system match (correspond to) images from the two eyes when both eyes are shown different viewpoints in 3D?

our visual system is able to detect specific features or parts of an object from both eyes together to form a single 3D object

Has the correspondence problem been resolved?

researchers are still trying to figure this problem out

What is another name for binocular depth cells?

disparity-selective cells

Where are binocular depth cells located?

primary visual cortex

What are binocular depth cells?

specialized neurons that respond to binocular disparity and specifically respond to absolute disparity