Mid-Level Vision, Color Vision, and Depth Perception

Object Recognition

The ability of the visual system to identify objects based on visual information.

V1, V2, V4, IT/LOC (Visual Areas)

Brain regions involved in visual processing.

V1

Primary visual cortex, processes basic visual information.

V2

Secondary visual cortex, processes more complex features.

V4

Processes color and form.

IT/LOC

Inferotemporal cortex and lateral occipital complex, involved in object recognition.

Dorsal vs. Ventral Pathways

Two major pathways in the visual system.

Dorsal (where)

Involved in spatial location and movement.

Ventral (what)

Involved in object identification.

RF Size (Receptive Field Size)

The area of the visual field that a neuron in the brain is responsive to.

Stimulus Invariances

The ability of the visual system to recognize an object despite variations in viewing angle, size, or lighting.

"Grandmother" Cells

Hypothetical neurons that respond to a specific, complex stimulus, such as a person's face.

Gestalt Principles

Principles that explain how the brain groups elements of a scene to perceive objects as a whole (e.g., proximity, similarity).

Nonaccidental Features

Features of an object that remain consistent regardless of the viewpoint (e.g., straight lines, corners).

Selfridge's Pandemonium Model

A model of object recognition based on a hierarchy of feature detectors (e.g., edge detectors, letter detectors).

Viewpoint-invariant Models

Models that propose the brain recognizes objects independent of their viewpoint.

Biederman's Geons

Simple geometric shapes that make up objects; essential for object recognition.

Color Metamers

Different combinations of wavelengths that produce the same color perception.

Trichromatic Theory

The theory that color perception is based on the activity of three types of cones (S, M, L).

Opponent Color Theory

The theory that color perception is processed in opponent channels (red-green, blue-yellow).

Cone-Opponent Cells

Neurons in the retina and LGN that compare the input from different types of cones to process color information.

Color Afterimages

The phenomenon where staring at a color for a long time causes the perception of its complementary color when looking away.

Hue Cancellation Experiments

Experiments that demonstrate how colors can be "canceled out" to reveal the underlying color perception.

Spectral

Related to the distribution of wavelengths of light.

Illuminant

The light source that illuminates an object, affecting its color appearance.

Power Spectrum

The distribution of light intensity across different wavelengths.

Absorption Spectra

The range of wavelengths absorbed by a particular material or photoreceptor.

Color Constancy

The ability to perceive the color of an object consistently despite changes in the illumination.

Color Blindness

A condition where individuals cannot perceive certain colors due to deficiencies in their cones.

Monocular Cues

Depth cues that require only one eye, such as size, texture gradient, and occlusion.

Binocular Cues

Depth cues that require both eyes, such as binocular disparity and convergence.

Stereopsis

The perception of depth created by the brain's processing of the slight differences between the images from the two eyes.

Horopter

The imaginary plane where objects are seen as having zero disparity, or the same location in both eyes' visual fields.

Panum's Fusional Area

The area around the horopter where binocular disparity is small enough for the brain to fuse the two images into a single percept.

Diplopia

The condition of seeing double, typically due to misalignment of the eyes.

Triangulation

A depth cue that uses the geometry of known objects and angles to infer depth.

Motion Parallax

A depth cue where objects closer to the observer appear to move faster across the visual field than objects farther away.

Optic Flow

The pattern of motion created by objects moving relative to the observer, used to estimate movement and depth.

Vergence

The simultaneous movement of both eyes toward or away from each other to focus on objects at different distances.

Convergence/Divergence

Eye movements that help to focus on objects either close to (convergence) or far from (divergence) the observer.

Random Dot Stereograms

Images made of random dots that create the illusion of depth when viewed with both eyes.

Real vs. Apparent Motion

Real motion: Actual movement of an object in space. Apparent motion: The illusion of movement when stationary objects are presented in different locations in quick succession.

Reichardt Detector

A model of motion-sensitive neurons that respond to motion by comparing signals from two cells with a temporal delay.

Motion Aftereffects

The phenomenon where, after viewing moving stimuli for a long time, stationary objects appear to move in the opposite direction (e.g., waterfall illusion).

Correspondence Problem

The challenge the brain faces in matching parts of objects in the visual field to track their motion across time.

First-Order Motion

Motion of an object based on changes in its luminance.

Second-Order Motion

Motion based on changes in the texture or contrast of an object, rather than luminance.

Vergence Movements

Eye movements where both eyes move in opposite directions to focus on nearby or distant objects.

Saccades

Quick, jerky eye movements that allow us to rapidly shift our gaze from one point to another.

Smooth Pursuit

Slow, continuous eye movements used to track moving objects.

Fixational Eye Movements

Involuntary movements of the eyes when fixating on a point, including microsaccades, drift, and tremor.

Efference Copy

A duplicate of the motor command sent to the eyes, helping the brain track eye movements and compensate for them.

Saccadic Suppression

The reduction in visual sensitivity during saccadic eye movements to prevent the perception of blur.