Module 18: Vision (221-236) =

Light Energy and its role in Vision (how is this related to color perception)

• Light energy is crucial for the process of vision.

• Light travels in waves.

• Wavelength is the distance from one peak to the next.

  • Determines hue, which is the color we perceive.

• Waves vary in length, affecting color perception.

Frequency and Wavelength Relationship: (higher vs lower frequency)

• Frequency is the number of complete wavelengths passing a point in a given time.

• Inverse relationship between wavelength and frequency.

  • Shorter wavelength = higher frequency.

  • Longer wavelength = lower frequency

Light Wave Amplitude (what does it determine)

• Amplitude refers to the height of the wave.

  • Determines intensity, or the amount of energy the wave contains.

• Intensity influences brightness.

  • Amplitude affects the perceived brightness of colors.

Pupil and Iris and Cornea (define them)

The cornea

• is the transparent outer layer of the eye that allows light to enter and helps in focusing images onto the retina.

The pupil

• a small, adjustable opening in the center of the iris. It regulates the amount of light entering the eye by dilating (expanding) or constricting (shrinking) in response to changing light conditions.

The iris

• the colored part of the eye surrounding the pupil. It is a muscle that controls the size of the pupil and regulates the amount of light entering the eye. The iris has unique patterns that are used for identifying individuals, and it can also respond to cognitive and emotional states, causing changes in pupil size.

Vision Conditions (close and far vision impairment, what are they called)

• Nearsightedness (Myopia)

  • Difficulty seeing distant objects.

• Far sightedness (hyperopia)

  • Difficulty seeing close-up objects

Johannes Kepler's Contribution (images in the retina) What did he disapprove of?

Johannes Kepler made significant contributions to our understanding of images formed in the retina. He disproved Leonardo da Vinci's idea that images in the eye are inverted. Instead, Kepler proposed that the retina receives images in their correct orientation, meaning they are not upside-down as previously believed.

Does the Retina see a whole image, why or why not

Retina doesn't see a whole image.

• since Retina is where the Receptor cells are, that convert light to impulses.

• Through the work of the receptor, bipolar and ganglion cells

• Rapid visual information processing

VI. Explain Dark Adaptation (what eye parts are important here, how long does it take for Full dark adaptation )

• Pupils dilate in a dark place to allow more light to reach the retina.

• Full dark adaptation takes around 20 minutes, matching natural twilight transition.

• Essential for adjusting to low-light conditions.

I. Hubel and Wiesel's Work - Feature detectors (where are they located, what do they do, receive info from what)

• Feature detectors: Nerve cells in the occipital lobe's visual cortex.

  • Respond to specific features like edges, lines, angles, and movements.

• Microelectrodes used to study feature detectors.

• Feature detectors receive information from individual ganglion cells in the retina.

• Supercell clusters in cortical areas respond to more complex patterns.

III. Fusiform Face Area (FFA) (where is this, what does it do, what if its damaged?)

• Located in the temporal lobe near the right ear.

• Enables perception of faces from various viewpoints.

• Recognizing faces from strangers and friends.

• Damage to FFA leads to difficulty recognizing familiar faces = prosoagnosia

  • inability to recognize family members, friends, or even oneself

  • cant still see faces tho (not blind to them, cant call it face blindness)

  • very small percentage have this condition (super rare)

IV.Due to the fact that Visual Perception analyzes motion, form, depth, and color simultaneously, what kind a processing is at play here?

• Brain achieves visual perception through parallel processing.

• allows the brain to analyze multiple dimensions simultaneously.

V. Grandmother Cells (define, why called grandmother cell?)

• Supercells, Requires significant brain power

• highly specialized neurons that exhibit an extraordinary level of selectivity in recognizing specific stimuli, often associated with complex and familiar objects, such as faces.

• The term "grandmother cell" implies the idea that there might be a single neuron or a small group of neurons dedicated to recognizing a particular concept or individual, like one's grandmother.

Figure and Ground - Gestalt Grouping Principles

• Definition:

  • The organization of the visual field into objects (figures) that stand out from their surroundings (ground).

• Perceptual Task:

  • In our high-level brain system, the first task is perceiving an object (figure) as distinct from its surroundings (ground).

Grouping Principles (3 main)

A. Proximity

• Definition: - Grouping nearby figures together. - Application: - Objects close to each other are perceived as related or forming a group.

B. Continuity

• Definition: - Perceiving smooth, continuous patterns rather than discontinuous ones. Application: - Our mind prefers to perceive continuous and flowing patterns in visual stimuli.

C. Closure

• Definition: - Filling in gaps to create a complete whole object. - Application: - When there are missing parts, our mind completes the form to perceive a cohesive object.

II. Gibson and Walk's Visual Cliff Experiment: Used a visual cliff, a simulated cliff covered by sturdy glass. Placed 16 to 14-month-old infants on the edge with parental coaxing. What were the results, what does this tell us about infants and depth perception?

• Results:

  • Most infants refused to cross, indicating early depth perception.

  • Support the idea that crawling infants and young animals can perceive depth.

III. Adolph's Study on Infant Motor Development. What is the relationship between crawling and depth

• Finding:

  • Crawling, regardless of when it begins, decreases infants' fear of heights.

  • Crawling involves looking downward, promoting hazard awareness.

Binocular Cues (name them, what is its limits)

Definition: Depth cues relying on the use of both eyes.

• Retinal Disparity (or binocular disparity)

  • Compares retinal images from both eyes.

  • The brain computes distance based on the disparity; greater disparity means a closer object.

  • cant be used to measure depth for movies (non pictorial)

Monocular Cues

Definition: Depth cues available to each eye independently. Can be either pictorial (2D) or non pictorial (3D)

Relative Height

• Objects higher in the field of vision perceived as further away.

• higher = far

• lower = close

• (pictorial)

Relative Size

• Assuming objects are similar, a smaller retinal image is perceived as further away (small = far) (big = close)

• (pictorial)

• NON ordinal

• Potential for yielding ratio information, unlike occlusion and height

Linear Perspective:

• Parallel lines meet in the distance; sharper convergence angle suggests greater distance.

• comes from relative size (part of)

• (pictorial)

Interposition/Occlusion:

• miswording here from Myers since occlusion occurs because of interposition

• Occurs when one object partially hides another

  • Look for T junctions

  • Pictorial

  • Provides ordinal information; indicates that one object is in front of another, but not by how much (cant measure/tell distance with it)

    • ordinal = order

• Found in early art, photographs, and films

  • partial occlusion has been found in art since paleolithic rimes where is it often used alone, with no other information to convey depth.

• Can be seen as the first source of informa­tion discovered

Texture Gradient

• Objects appear larger, more spaced out, and more detailed when they are close to the viewer.

• As the surface extends into the distance, the elements become smaller, closer together, and less detailed.

• means relative density

• comes from relative size (part of)

• (pictorial)

Shape from Shading

• shape based on variations in brightness and shading on a surface.

• tell us depth from different parts of the object with whats shaded or not

• (pictorial)

Familiar Size

• brain knows (have past experience/memory of size)

• know what size a certain object is

• can find metrically (exact) distance if you already know the size

• (pictorial)

Ariel or Atmospheric

• hazy = far and clear = close

• Hazy, Bluish Distant Objects: When you look at distant objects, their light has to travel through a larger portion of the Earth's atmosphere. the shorter blue wavelengths are scattered more, causing distant objects to exhibit a bluish tint.(more or less) (far = blue tint)

• pictorial)

• Weak, just like relative density — (Weaker perceptual potency)

Accommodation

• Focusing on Near Objects: ciliary muscles contract. causes the lens to become thicker, increasing its refractive power.

• Focusing on Distant Objects: ciliary muscles relax. causes the lens to become thinner, reducing its refractive power

• (non pictorial)

Vergence

• convergence = outward (see something near)

• divergence = inward (see something far)

• (non pictorial)

Motion Parallax (what can be used to achieve this)

• far things = slow

• close things = fact

• things dont look like there moving, if you keep fixation on it (depends on fixation point)

• (non pictorial)

• Best seen during a dolly (tracking) shot, creating an impression of self-movement

• Specifically does not refer to the motion of a given object — its the motion of you looking at stationary objects (ex: like when driving)

I. Motion Perception: Stroboscopic Movement and Phi Phenomenon and Size and Speed Perception:

Size and Speed Perception: (large vs small objects and speed)

• Large objects moving at the same speed as small objects appear to move more slowly.

Stroboscopic Movement

• Phenomenon where a rapid series of slightly varying images is perceived as continuous movement — Creates Apparent Motion

• closely related to the phi phenomenon

III. Color Constancy

• Definition:

  • Perceived color remains constant despite changes in lighting.

  • the color doesnt change, the lighting does (illuminant changes)

  • same type of argument as size constancy

  • Explained by Land

V. Shape and Size Constancies

Shape Constancy:

• Perceiving the form of familiar objects as constant, even with changing retinal images.

• Visual cortex neurons rapidly learn to associate different views of an object.

Size Constancy:

• Perceiving an object as having an unchanging size despite variations in distance.

• perceived size doesnt change the distance does

• same type of argument as color constancy

Perceptual Interpretation and Development ((Nativist vs Empiricist)

I. Philosophical Perspectives:

Nativist):

• Knowledge is derived from inborn ways of organizing sensory experiences.

(Empiricist):

• Argued that through experiences, we learn to perceive the world.

• born as a blank slate

Stratton's Experiment : Glasses changing he whole world. Was Given glasses that turned the world upside down. What was the results?

• Demonstrated the remarkable adaptability of humans in adjusting to new sensory contexts.

• Initially challenging, but over time, coordination improved.

The depth cues that can be seen in movies

1. relative size

2. familiar size

3. ariel perspective

4. relative height

5. occlusion / interposition

6. shape from shading

7. Motion parallax

What are the depth cues that is not applicable for film and pictures

Can only be used to measure depth in real life, cannot do it through pictures or movies

1. Vergence (monocular, non pictorial)

2. Accommodation (monocular, non pictorial)

3. retinal disparity (binocular)

• and while motion parallax does not work for pictures (non pictorial) it still works for movies

  • this is done using sequence of images that is then played fast enough to give relative motion

  • things dont look like there moving, if you keep fixation on it (depends on fixation point)

  • so movies can keep fixation point by rotating the camera

Do these monocular cues find the distance or the size of an object first?

• first the depth (distance) is figured out

• depth is then used to know the size (apparent size)

Functions of V1 and V2 (what happens if damaged)

Also known as the striate cortex

V1 (Primary Visual Cortex)

• initial processing of basic visual information, such as edges, orientation, and simple shapes.

• Feature Detection: involved in detecting specific visual features, including edges, contrasts, and orientations. essential for recognizing objects and patterns

• facilitates binocular vision and depth perception. (receive input from both the left and right eyes)

V2 (Secondary Visual Cortex):

• builds upon the basic features extracted in V1 by processing more complex features, such as contours, textures, and patterns

• combining information from different parts of the visual field.

• crucial for integrating form and color information (color processing)

• contributes to stereoscopic depth perception by processing binocular disparity.

If either Damaged…

• Both give output to solve stereopsis so if damaged, will lead to stereo blindness, where you are cortically blind since everything goes through here

Area MT or V5 (what happens if damaged)

Also known as extra striate

• needed for motion perception

• Middle temporal cortex

• gets info from both eyes

• integrates motion information across the visual field

• closely associated with the control of smooth pursuit eye movements

Implications of Damage:

• can impact the ability to smoothly track moving objects with the eyes. (impact smooth pursuit ability)

• Can lead to a condition known as akinetopsia or motion blindness

  • have difficulty perceiving and recognizing motion

  • static visual perception remains intact

Area V4 (what happens in damaged)

• needed for color constancy and color processing

• area in the visual cortex

• also for form perception

• deals with the visual receptors (cones for color)

Damage

• leads to difficulties in color perception

• often caused by genetic factors

• more common in males. (1 in 12 males are color blind).

What are the 3 types of color blindness, explain them

Monochromacy:

• total color blindness

• only one type of color receptor or cone in the retina.

• see the world in shades of gray and lack the ability to perceive color.

  • Achromatopsia: total absence or severe reduction of color vision. see the world in shades of gray

Dichromacy:

• has two types of color receptors instead of the normal three.

Protanopia

• Lacking or malfunctioning red-sensitive cones (difficulty perceiving red light).

Deuteranopia

• Lacking or malfunctioning green-sensitive cones (difficulty perceiving green light).

Tritanopia

• Lacking or malfunctioning blue-sensitive cones (difficulty perceiving blue light).

• Individuals with dichromacy can still perceive some colors, but their color vision is limited compared to individuals with normal trichromatic vision.

Perceptual Control Theory

• seek out-certain stimuli

• developed by William T. Powers, behaviorist

• focuses on the idea that organisms are driven by a need to control their perceptions rather than their behavior

• notion of a control system, a set of processes that function to maintain a particular state or goal.

Aperture Problem

• when a Aperture is placed, we dont know how things are moving cus of small opening

• eyes and cameras have Apertures

• visual system has limited information about the direction of movement of an object,

Correspondence Problem

• encountered in stereovision (Correspondence Problem involves finding the corresponding points in the left and right images)

Reflectance x Illuminant = Color Constancy

• a simplified representation of the concept of color constancy (what V4 does) in computer vision and color science.

• Its reflectance properties (how much light is being reflected or absorbed) and the illuminant (light source intensity/wavelength size) together determine the perceived color.

• V4 separates these 2 things to calculate

Additive VS Subtractive color mixing

Additive Color Mixing:

• TV, computer screens, stage lighting

• colors are created by combining different amounts of light

• red, green, and blue (RGB) — dont use pigments, use light sources

• Process: As more light is added, the colors blend together to create white

Subtractive Color Mixing:

• Paints, color printing (use pigments, not light sources)

• Each color absorbs some light, so when you mix them, they absorb even more light, making a new color.