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absence of motion - might see “frozen” snap shots instead
Motion blindness; inability to perceive motion, as demonstrated in the case of L.M., who struggled with daily tasks post-stroke.
signals or cues that indicate when one action or event ends and another begins.
Perceived motion continues in the observer’s mind, influencing time judgement.
tendency for the mind to continue perceiving motion even after an object has stopped.
what it does: signals that the eyes are moving
when does it happen: when you move your eyes, but the scene stays the same
ex: Following a moving car with your eyes → You don’t see the background “move” because the brain knows your eyes are moving
Single neuron responses can be ambiguous due to limited receptive fields.
When an object moves, a neuron in the visual system can only see a small part of it (like looking through a tiny window). Because of this, the neuron can’t tell the object’s true direction—it only detects motion along the edge it sees. The brain solves this by combining signals from many neurons in higher areas like MT (middle temporal area).
happens when you look through a circle you make with your fingers, and move a pencil horizontally or diagnonally
The perception of depth due to binocular disparity.
how we see depth using both eyes. Since our eyes are slightly apart, each sees a slightly different image. The brain compares these images to create a 3D view of the world.
They are brain cells that detect small differences between what each eye sees (binocular disparity) to help us see depth and distance.
binocular disparity
the difference between the image on the Left retina and the image on the Right retina
protanopia
Missing red (L) cones → difficulty seeing reds, confusing reds with greens.
deuteranopia
Missing green (M) cones → difficulty seeing greens, confusing greens with reds.
tritanopia
Missing blue (S) cones → difficulty seeing blues and yellows (very rare).
Horopter
imaginary line where objects are at the same depth as the point you're focusing on. Objects on this line create identical images in both eyes (no disparity).
When an object is far from the horopter, the images on each eye are more different. The brain detects this difference (disparity) to judge depth.
Closer to horopter → Less disparity (images are similar)
Farther from horopter → Greater disparity (images are more different)
corresponding points
pair of points that would overlap if you slid one retina on top of other (aligned at foveas)
apparent movment
still images shown quickly create the illusion of motion (like flip book or movie)
Induced movement
a moving background makes a still object look like its moving (like the moon seeming to drift when the cloud moves)
eg; pigeon walk - head first then body (head appears to move backwards)
image displacement signal
What it does: Signals that something moved across the retina
when does it happen: when an object moves while your eyes stay still
ex: A person walks across your field of view while your eyes stay still → The image moves across the retina
Kinetic depth effect
2D shape appears 3D when it moves. motion provides depth cues that the brain uses to perceive structure
correspondence problem
happens when the brain tries to match up parts of two images to perceive motion or depth, but it’s not always clear which parts go together.
metamers
physically different, but perceptually identical colors—they look the same because they stimulate the cones in the same way.
ex; A yellow light vs. a mix of red + green light—different light sources, but they look the same
X & Y axis - spectral power distirbutions
X - axis: wavelength (400-700nm)
Y axis: power (intensity of each light at each wavelength)
X & Y - reflectance functions
X-axis: wavelength (shows visible light wavelengths)
Y-axis: reflectance (%)
motion produced depth cue
when movement helps us perceive depth and distance. These cues include:
Motion parallax – Closer objects move faster across our vision than distant ones.
Deletion & accretion – Objects appear or disappear behind others as we move.
Opponent process theory
color perception is based on opposing neural signals
Red Vs Green (R+/G-)
Blue vs Yellow (B+/Y-)
Black vs white (luminance)
motion produced depth cue
where motion helps us judge distance.
Types:
-Motion Parallax – Closer objects move faster than distant ones. (Example: Trees near the road zoom by, but mountains move slowly.)
-Deletion & Accretion – Objects appear or disappear behind others as you move. (Example: A pole blocking and revealing objects as you walk.)
illusory motion aftereffects
after looking at motion for a while, you see motion in the opposite direction when the motion stops.
movement aftereffects
After watching actual motion, you see illusory motion in the opposite direction when the motion stops.
Opponent neurons code for opposite directions (e.g., upward & downward).
Watching continuous movement causes one set of neurons to fatigue.
When motion stops, the opposite neurons fire more, creating the illusion.
locomotion
ability to move from one place to another using body movement.
figure/ground segregation
The ability to separate an object (figure) from its background (ground), often using motion or perceptual cues.
inhibitory connection
when one neuron reduces or suppresses the activity of another neuron.
excitatory connection
when one neuron increases the activity of another neuron, making it more likely to fire.
V1
(Primary Visual Cortex) is the first stop for motion processing.
It detects basic motion direction and edges of moving objects.
Sends motion information to MT (Middle Temporal area) for further processing.
MT (dorsal)
(Middle Temporal area) is a key motion processing center in the dorsal stream.
It specializes in detecting object movement, speed, and direction.
Helps with tracking moving objects and understanding motion in space.
Occlusion heuristic
the brain’s assumption that when one object partially covers another, the hidden object continues behind it.
Parvo streams
detects edge-information by processing things like colour.
processes color, fine detial and texture
slow but detialed
best for static objects, recognizing faces, reading
ventral (what) pathway
Magno streams
detects motion – cannot detect edges based only on colour (needs luminance contrast).
proceses motion, brightness and fast changes
fast and less detailed
best for moving objects, detetcing motion & depth
dorsal (where/how pathway) -
Ouchi illusions
creates a false sense of motion or depth, making the center disc appear to float or move over a checkered background.
Why does this happen?
When you move your eyes, different motion signals occur in the center vs. the background.
Horizontal and vertical patterns interact, confusing the brain’s motion detection system.
Common fate principle: The brain treats the center and background as separate objects, making the center seem like it moves.
expansion (loom)
• Moving forward in space (toward central dot)
• Perceive motion outward from that goal point.
• Each point in image is moving AWAY from center
Corresponds to an object increasing in size as it approaches you
contraction (receding)
• Moving backwards
• Perceive motion inward to central point
Corresponds to the scene decreasing in size as you move away from it
chromatic
contains color - red, blue etc (wavelengths of light that the eye perceives as color)
achromatic
lacks color; only shades of black, white and gray
isaac newton
• Prism bends each wavelength of light by a different amount.
• Short wavelengths more than long.
• Decompose white light into red green blue etc. component
the components of the rainbow are the fundamental constituents of light
light is unaffected by a second prism (first prism already separated it into its fundamental components)
a prisms effects are reversible - the light isnt destroyed by the first prism
monochromatic light
consists of only one wavelength of light, meaning it appears as a single, pure color.
reflectance
percentage of light that bounces off an object instead of being absorbed.
Key points:
High reflectance = Appears brighter (e.g., white paper reflects most light).
Low reflectance = Appears darker (e.g., black fabric absorbs most light).
Selective reflection: Some surfaces reflect certain wavelengths more, which gives them color (e.g., a red apple reflects red wavelengths more than others).
specificity coding
idea that a single neuron responds only to a specific stimulus (e.g., one neuron for recognizing your grandma).
ratios
comparative relationships between different sensory inputs or stimuli, like the ratio of light intensities, distances, or other physical properties that the brain uses to process and interpret information.
ratios of activation
relative amounts of activation or stimulation of the different cone types in the retina (cones for red, green, and blue light). These ratios help the brain recognize colors, even when the light intensity changes.
monochromats
have no cones (only rods)
dichromats
only 2 cone photopigments (not 3)
hering & circuits
proposed 3 “opponent” processes:
red-green - worse acuity
yellow-blue - worse acuity
black-white (luminance) - best acuity
simultaneous
happening at the same time
successive
one thing happening after another
perceptual constancy
we perceive properties of objects as remaining constant
color constancy
we percieve an objects chromatic color as remaining constant
melanopsin
light-sensitive protein in the eye that helps detect light, especially blue light, and regulates circadian rhythms (sleep-wake cycle).
opsins
light sensitive proteins
Rhodopsin (rods)
photopsin (cones; 3 types)
accommodation
lens changes shape to focus on nearby objects
convergence
eyes move inward so image of nearby objects falls on both foveas
motion parallax
nearby objects move faster than farther away objects
deletion
When an object moves out of view, its parts are "deleted" or hidden. This helps us understand the motion of an object.
accretion
When an object moves into view, its parts become visible. This helps us detect new information about an object's movement.
Julesz
known for his work in random dot stereograms
His work showed: The brain is capable of perceiving depth and motion using simple visual cues, like changes in pattern or dots.
size distance scaling
taking objects distance into account when estimating its physical size
Muller-lyer
visual illusion where two lines of the same length appear to be different due to the arrow-like figures at the ends.
ponzo
visual illusion where two horizontal lines of the same length appear to be different because of the converging lines (like railway tracks) in the background.
ames room
distorted room used in visual perception experiments to create a size illusion.
autostereograms
images designed to create a 3D effect when viewed in a specific way, without the need for special glasses.
