S&P exam 3 - ch 9 , 10 , 15

Color perception

The ability to perceive differences in color wavelengths and identify objects based on their color.

Perceptual grouping

The process of organizing and grouping features of objects based on visual cues.

• Example: The result was that observers recognized the appropriately colored objects more rapidly and accurately. Thus, knowing the colors of familiar objects helps us to recognize these objects.

• color also helps us recognize natural scenes and rapidly perceive the gist of scenes.

Visual cue

A signal that helps grab your attention and organize visual perception.

Familiar object recognition

The ability to recognize objects more rapidly and accurately when they are displayed in their typically associated colors.

Monochromatic

Refers to animals that possess only one type of photoreceptor, allowing them to see only one color.

• aquatic animals

  • dolphins have only one type of chrome cells

Dichromatic

Refers to animals, such as dogs and bears, that have only two types of photoreceptors for color vision.

Trichromatic

Refers to species like humans and monkeys that have three types of photoreceptors for color vision.

Light spectrum

The range of wavelengths of light, which corresponds to different colors perceived by the human eye.

• Color is a mental response

• We have evolved to respond to the color wavelengths

• Starts with a light source

  • White light is made up of all the frequency’s at the same levels

Selective reflection

The process by which objects reflect certain wavelengths of light while absorbing others.

• example: All frequency’s hit the apple, the apple absorbs most of the color frequency’s and then reflects the color red and doesn’t absorb it

Achromatic color

Colors that do not correspond to specific hues on the light spectrum;

include white, grey, and black.

• Reflectance curve is a flat line because it’s equally reflecting all the different parts and colors from the light spectrum

• More or less dependent on how dark or light the grey is

Reflectance curve

Graphs that depict how much light of different wavelengths is reflected by a surface.

Selective transmission

The process through which certain wavelengths of light pass through an object, absorbing all parts of the spectrum.

• not bouncing off and hitting your eye

Subtractive color mixing

A method of color mixing where pigments absorb (subtract) certain wavelengths of light, resulting in combined colors.

• Each components is subtracting out the spectrum of light but is leaving behind the little bit that isn’t being taken away

  • Mixing colors together ; paints

  • End up with black

Additive color mixing

A process where colors are created by mixing lights together, resulting in a lighter / white mixture.

How do we distinguish colors?

Through the dimensions of color;

1. Hue,

2. Saturation,

3. and Lightness / Value

Hue

The attribute of color that allows us to differentiate one color from another,

• such as green from blue.

Saturation

The intensity or purity of a color, describing how vivid or dull the color appears.

Lightness (value)

The perceived brightness of a color, influenced by the addition or subtraction of grey shades.

Trichromatic theory of color

The theory that color perception is based on the combination of three independent, primary colors:

• red, green, and blue

Young-Helmholtz theory of color vision

A color vision theory suggesting that one cone on its own can’t tell you anything about what color you’re perceiving;

→ you need three different types of cones that vary in brightness that correspond to red, green, and blue light.

• Refers to the wavelengths of lights

• Color matching studies

  • example: Give someone a reference color and then give them control over different colors of lights and they try to recreate the standard color you gave them with adjusting the lights

    • If you give them three colors then they could match any color, compared to if you gave them two or more than three, they wouldn’t be able to recreate a color

S-cones

Photoreceptors sensitive to short wavelengths of light, primarily blue.

M-cones

Photoreceptors sensitive to medium wavelengths of light, primarily green/yellow.

L-cones

Photoreceptors sensitive to long wavelengths of light, primarily yellow/red.

• example: Perception: When cones are hitting at the yellow, there is an equal firing response from L and M cones because it is hitting the same level of sensitivity

Metamers

Different wavelengths of light that are perceived as the same color due to the response of the cones.

• Red, green, and blue are metamers of white

Color deficiencies

= total / partial color blindness

A condition from birth where individuals perceive colors differently than normal because of the genetic absence or malfunction of one or more types of cone receptors.

Monochromatism

= color blindness

A form of color blindness where an individual can only see shades of gray / darkness because they only have rods and no cones at all.

• Can’t distinguish color from any other color

• Very rare

• Can make out shapes but everything would be very blurry

• Very sensitive

• Poor acuity / clearness

Dichromacy

A color vision deficiency when having only two color receptors instead of three.

• can be any of these they are missing:

  • Protanopia

  • Deuteranopia

  • Tritanopia

Protanopia

impairment of the L cones

Deuteranopia

Missing M cones

Tritanopia

Missing S cones

Unilateral dichromats

Individuals who have dichromacy only in one eye while the other eye has normal color vision.

• Normal trichromatic (three cones) in one eye and the other eye has dichromacy (only two cones)

Ishihara plates

A set of color vision tests used to diagnose red-green color deficiencies.

Anomalous trichromats

Individuals who have three types of cones, but the sensitivity of one cone has shifted, overlapping with another; causing color vision anomalies / abnormalities.

Sex-linked conditions

Genetic traits that are located on the X chromosome, often affecting males more severely.

• Genetic females could still have normal vision since they have one normal X chromosome even if the other X is infected.

• Females could only really get it if they inherit both X chromosomes being infected

• Males are more likely to get it because they only have one X chromosome so if they inherit it they will definitely have it while females are 50/50

Color afterimages

Showing the opposites of the colors you’re going to see because the opposite of that color is what is still lingering

Opponent process theory

A theory that suggests color perception isn’t made up of the three colors; its made up of colors that oppose each other

• Dimensions of opposing colors combine to form our color perception

  • such as red versus green and blue versus yellow.

Hue cancellation studies

A method where one color is used to counteract another, demonstrating the opponent process of color perception.

• Added yellow light to try and cancel out the blue color

• Can cancel out yellow with blue – vice versa

• Can cancel out red with green – vice versa

  • Opposites don’t exactly match up with green and red

  • Red is the opposite of a light blue and green is opposite of a magenta

Different “theories” of color

Turns the trichromatic three cones (independent of each other) into the opponent process (blue vs yellow) which is what is then sent to your brain

• How much yellow is there vs blue is what is sent to the brain

Impossible colors

Some combinations that are just not physically possible in the real world because of the way the cones overlap and interact with each other

• True cyan: S and M cones, with no L

  • Whenever you see cyan in the real world; the color is being desaturated / washed out some

How do you go from trichromatic to colors vs other color?

Has to do with;

• receptive fields,

• center surround fields,

• single opponent fields, and

• double opponent fields

Receptive fields determine what?

= they determine acuity

separate receptor fields in parts of body that have good acuity like in the fingers but in body parts with less acuity like the arm the receptive fields are much bigger and overlap a lot

= Combining their information together that leads to one signal

Center surround fields

• Have one kind of connection in the middle and a different on the outside

  • Inhibitory on outside

  • Excitatory on inside

Single opponent fields

respond to colors of broad / large areas

• Still has excitatory and inhibitory sections but on top of that, the signals are excited by different color factors

  • Center is excited by M cones (green)

  • Outside is excited by L cones (red)

Double opponent fields

respond to color patterns, textures, and color boundaries, and detecting edges.

• It would lead to no response at all because the signal from the one side is going to be completely signaled out by the color from the other side

  • Would get an inhibitory response if the red is against the green since the M is – in the red block so it would fire negatively

  • Would get an excitatory response if there is a boundary between the two colors; red and green

    • Responds strongly to the boundary between two colors

    • Does not respond to solid colors

• example: The boundary is being detected by our double opponent field which is why the white inside looks more orange than the white outside since it is lined with a boundary of orange vs purple

Color constancy

The ability of the visual system to still recognize and detect the color itself, despite changes in environment or to it like the color of the light above

• in example picture, can still tell that the color is red when there is a blue or green shade overtop of it but the red is actually a very dramatic change from the original red

  • We are compensating for the color of the lighting that we see in the picture

    • Mind is trying to compensate by subtracting out the blue light that is covering it which leads you to the original color; being red or yellow

    • Your mind perceives it as yellow even though it is actually a greyish

Chromatic adaptation

Similar to the ‘color after effect’ where ; you’re adapting to a color after looking at it for a while, and then after your receptors just don’t react as strongly as they did

• Can also partly explain what’s happening in the images covered by a different color light

Real world situation: under different shades of white light in a room or during “golden hour” from the sunset or sunrise outside

Lightness constancy

accurately being able to detect the lightness of an object despite the brightness of light that is hitting it is changing

• Black absorbs most of the light but not all of it

• White reflects most light

Reflectance

amount of light being reflected by white vs black

Illumination

how much light is hitting the object in the first place

• The factors of light (sun outside vs lights in a room) changes the amount of light being reflected off and is hitting your eye

  • Sun is much brighter than the lights in a room

    (image)

  • The amount of light reflecting off of black when its being hit from the sun can be a lot higher units than the amount of white units that are bouncing off a white object when in dimmer, inside lighting

    • Depends on the amount of light hitting it

Ratio principal

lightness perception is based on the ratio between an objects light intensity and the light intensity of its surroundings

• (image) ‘A’ and ‘B’ are actually the same color but they don’t look like the same color because of its surroundings and our mind making ‘B’ look lighter than it actually is since we see there is supposed to be a shadow over it

Reflectance edge

A boundary / edge caused by a change in the reflectance properties / change in actual color of object

• that creates a visual contrast between two areas due to differing reflectance levels.

Illumination edge

a visual boundary where the amount of light (or illumination) changes abruptly.

• A boundary / edge created in a scene where difference in brightness is caused by illumination ; objects color are both the same but more light is hitting one, making it look brighter or darker

• Dress example: The reason people can see it different ways is because of color constancy

  • When seeing blue and black; mind is compensating by subtracting out the bright yellow light from the background

  • When seeing yellow and white; mind is seeing it being under a shadow so you’re compensating and brightening the colors up

Identifying shadows

• Penumbra: The fuzzy border around shadows edge

• Meaningful shape:

• Orientation of the surface: What direction is the surface pointing

Ponzo illusion

An optical illusion with objects along converging lines; when something is farther away it looks bigger to you

Shepard illusion

An optical illusion that tricks / compensates for your depth perception, making two objects appear to be different sizes even when they're the same.

Muller-Lyer illusion

An optical illusion where length perception is affected by arrow shapes at the ends of lines pointing inwards or outwards;

• perceive the line where its pointing outwards as longer compared to the line with arrows facing inward when they’re actually the same size

Conflicting cues theory

because one object is bigger overall then we are using that as an extra piece of information to judge how big the line is

Ames room

gets rid of any depth information that tells you that one side of the room is closer to you than the other.

• Tricks you into thinking two things are the same distance from you, making you think one is much bigger

Familiar size development

When babies learn to develop familiar size cues

• Played with toys of different sizes

• 5 months they don’t show the effect, just as likely to grab for either one

• Couple months ~7 months later they learned how to use the distinction of familiar size and grabbed the bigger one first, thinking it was closer to them

Shadow development

Same age range of when they learned how to take advantage of the shadow information, thinking the one with deeper shadows was closer to them

Cutaneous senses

= skin senses

Completely different types of signals that pick up different types of information

The senses responsible for the perception of;

• Pressure

• Vibration

• Pain signals

• Temperature

• Itching

• Proprioception

  • Knowledge of where your body is in space

Cutaneous perception

Made up of sensory information that you can get from your skin and your body

Mechanoreceptors

receptors in the skin that respond to mechanical information

• Can involve pressure, movement, vibration, and stretching

  • (physical force & motion on your skin)

Slowly adapting receptors (SA)

Receptors that continue to respond to a stimulus as long as it is present.

(respond to pressure stimuli)

• Example: Something is pressing on you for a second and then it goes away

• These receptors are going to start firing when the pressure starts and then keeps firing the whole time something is touching you

Rapidly adapting receptors (RA)

Receptors that respond quickly to changes in stimulus but adapt to constant stimuli.

(responds to changes in pressure stimuli)

• Start firing as soon as contact starts but almost instantly stops firing and then starts firing again when the pressure stops

• Get used to the stimulus really quickly and fires again when there is another change in pressure / when the stimulus is taken away

  Has squishy stuff around it: (image)

  • Example of hand in a water balloon, you’d feel if someone’s hand was pressing down on the balloon and then wouldn’t feel it if they kept their hand there but then once they took their hand off you’d feel it and the water would move around

What are the two senses near the surface of the skin?

Merkel receptors (SA1) = slowly adapting receptors 1

• Good at picking up fine detail

Meissner corpuscles (RA1) = rapidly adapting receptors 1

• Important at detecting motion on your skin

• Useful at adjusting hand grips because pf the change

What are the two senses deeper down in the skin?

Ruffini Cylinders (SA2) = slowly adapting 2

• Good for detecting stretching in your skin

Pacinian corpuscles (RA2 / PC) = rapidly adapting 2

• Important for detecting vibration / a pressure that is coming and going quickly

• Detect fine texture

Homunculus

= little man / map of human body inside of your head

• The way it is like the body is that the responding areas are mapped out in the same order for the most part

• But.. there are a few body parts in the cortex that are out of order

• The size of each area is also not correlated to the bigger body parts

  • in the; Primary somatosensory cortex / receiving area / S1

  • Soma = body, so = body senses

Cortical magnification

The phenomenon where certain body parts have a disproportionately large area dedicated to processing sensory information in the brain.

• The reason the body parts like hands have bigger areas in the brain than say the leg is because you have better perception in those parts of your body

Experience-dependent plasticity

The brain's ability to change and adapt based on individual experiences, particularly in sensory processing.

• Example: Monkeys trained for 3 months on task involving index finger

• Results showed that there was a change in how much of the brain is designated to a certain body part just from their experience

Tactile acuity

The level of small detail that you can pick up and be perceived through touch, which varies between different body parts.

Grating acuity

A way to measure tactile acuity

• example: A measure of spatial resolution based on the participant’s ability to identify the orientation of lines.

  • the participant would tell you if the lines of the grating were horizontal or vertical

Two-point threshold

A measure of tactile acuity that indicates the smallest distance between two points that can be perceived as separate.

• measuring with an “aesthesiometer” where you can adjust the two points where it ends up feeling like one point instead of 2 and can measure how close or far apart it has to be to still be able to tell its 2 points

• Have really small two point threshold for fingers but compared to the arm the threshold number is much higher so it’s harder to detect if its two or one points

• This relies on the Merkel receptors (SA1) because of the amount of these receptors in a certain space

Merkel receptors (SA1)

Slowly adapting mechanoreceptors that provide detailed information about texture and fine touch.

• is what makes each body part and persons two point threshold a little different because of the amount of these receptors in a certain space

  • These receptors are more spaced out in the arm then they are in the fingertip

  • Pinky and index finger have same number of Merkel receptors but your index finger has better acuity than the pinky because of the experience and use – like how it was in the monkey tactile acuity study

Texture senses

= detecting repeating patterns of fine details

1. Ruffini cylinders (SA2)

2. Pacinian corpuscles (RA2 or PC)

Pacinian corpuscles

Rapidly adapting mechanoreceptors that are good at picking up fine textures because they can detect vibrations

• example: when pressing down on fine parts of sandpaper, people couldn’t tell the difference in fine textures just by applying pressure

  • But could tell the difference with movement

  • This is because it is able to be transmitted through vibrations

Spatial cues

texture features that are large enough to detect with stationary pressure

Temporal cues

smaller texture features that are detected through movement

Texture perception example study

turning off people’s ability to detect vibrations to see if they were still having the same results of telling the differences between different grids of sandpapers.

• When exposing them to 6 minutes of 250 Hz of vibration the PC cells adapted because they were overwhelmed which caused them to not be able to feel the vibrations anymore and not be able to tell the difference between the sandpapers

Haptic perception

perception based on exploring objects in the world through touch.

Involves multiple systems:

• Somatosensory system

• Motor system

• Cognitive system

Motor system

moving around to be able to feel different parts of the object to get the information you need

Cognitive system

doing trial and error, feeling different parts of the object, and coming up with ideas of what it could be

Exploratory procedures

Methods used to explore objects via touch to gain information about their characteristics.

• lateral motion

• pressure

• enclosure

• contour following

Lateral motion

Moving fingers across a surface to get tactile information about texture.

Pressure

Tells you about the density of object

(hard like rock or soft like sponge)

Contour following

The tactile exploration method used to identify the shape of an object by tracing its outline.

Inverse projection problem

makes depth perception harder

• Makes a 2D picture on your retina

• Information you have on your eye is incomplete / ambiguous; can interpret it in any way

  • Hollow mask illusion: mask looks like it is sticking out on the hollow side, fooling your mind

• No single solution

• We rely on many different sources of information at once

Oculomotor cues

Cues that make use of the information using the muscles in your eyes

• Paying attention to the tension in your eyes and using that to know how far or close something is

• Can put strain on your eyes which helps you detect how close or far an object is

Convergence

How your eyes aren’t always looking straight ahead; they’re focused inwards a little; so both can be looking at the same thing

• The closer the object moves to you, the more your eyes turn in

Accomodation

When something goes out of your eye it goes out of focus so you have to squeeze the lens to focus;

making you tense up those eye muscles which you can detect

Monocular cues

can tell the depth even if you’re looking at it with one eye

Pictorial cues - relative size

the farther away an object is from you, the smaller it is

Pictorial cues - relative height

lower on the visual field = closer, higher up = farther away

• for things that are above the horizon

• the closer it is to the horizon, the farther away it is / farther from the horizon = closer to you & bigger in your vision

Pictorial cues - Occlusion

“occluding your view” / “blocking your view” when something is covering something else, it is closer to you than what its blocking

Pictorial cues - Perspective convergence

parallel lines come together as distance increases; they meet at the —>

vanishing point = where all converging parallel lines come together at

Pictorial cues - familiar size

using knowledge of how big things actually are to figure out how far away they are.

• example: if a basketball and golf ball are both technically the same size on your visual field, then the golf ball is closer because it is much smaller than the basketball

Pictorial cues - texture gradient

elements of patterns get smaller and more densely packed as they get farther.

• works on a big scale

Pictorial cues - atmospheric perspective

as stuff gets farther from you it looks hazier and lighter

• from particles in the air and atmosphere

• works on a big scale

Pictorial cues - shadows

changes your perception of where the object is moving or is placed in space

What uses all the Pictorial cues?

The Renaissance pictures use all of the Pictorial cues.

• and uses them really well;

• making it look more realistic