Week 2 pt 2 Depth and Distance Perception

Flashcards covering terminology, oculomotor, pictorial, stereoscopic, and motion cues to depth and distance perception, as well as experimental findings on action vs. perception.

Egocentric distance

The distance between you and an environmental object.

Exocentric distance

The distance between two environmental objects.

Absolute Egocentric Distance

The distance of an object from you in absolute units, such as meters.

Depth

Relative distances between pairs of objects, such as distance cb being $3 \times$ larger than distance ab.

Depth Order

Determining simply which of different objects is nearer.

Oculomotor Cues

Feedback from eye muscles consisting of convergence and accommodation, which are only effective when objects are $1-2\,m$ away.

Pictorial Cues

Also called Monocular Depth Cues, these are based on the principles that objects are opaque and retinal image size decreases as distance increases.

Occlusion

A pictorial cue that gives us only depth order information by showing which object is in front.

Relative Size

A pictorial cue that provides information about the relative distance between objects.

Familiar Size

A depth cue where knowledge can influence perceptions of depth, though it is a much weaker cue than relative size.

Texture gradients

The appearance of equally spaced texture elements packed closer together as distance increases, used to scale distance, size, and slant.

Perspective Gradient Cue

A cue first described by Leon Battista Alberti ($1435$) where parallel lines appear to converge to a single point as distance increases.

Compression Gradient Cue

Also known as Foreshortening, this occurs when projected depths of objects diminish according to the square of their distance, decreasing vertical separation between horizontally oriented lines.

Visible horizon

The most distant visible boundary in the scene.

True horizon

A point representing optical infinity formed by parallel lines on the ground plane converging to vanishing points.

Height in Visual Field Cue

A cue where objects above the horizon appear further when they are lower, and objects below the horizon appear further when they are higher.

Horizon Ratio

The constant ratio of the amount of an object above to the amount below the horizon as its distance from the observer increases.

Atmospheric perspective

A cue where distant objects appear less clear due to more particles in the air between the observer and the object.

Shading and lighting

Patterns of light and shadow that provide info about relative depth, based on the brain's typical assumption that the light source is above us.

Binocular disparity

The difference in the horizontal separation between images of two objects in the left and right eyes, calculated as $\alpha_L - \alpha_R$.

Motion Parallax

A monocular cue where nearer parts of a moving scene appear to move faster than further parts.

Motion Parallax Directional Rule

Objects further than the fixation point move in the same direction as the observer's head, while objects closer than fixation move in the opposite direction.

Kinetic Occlusion Cue

A cue provided by moving objects that includes accretion and deletion information, which is stronger than static occlusion.

2-Streams Hypothesis

The proposal that different visual pathways are responsible for perception and action.

Blindfolded Walking Experiment

A study showing that people often underestimate distance in verbal estimates but are accurate when walking to a target with eyes closed.

Goldstein's view of visual processing

The theory that the main goal of visual processing is not conscious perception, but to control navigation, catch prey, avoid obstacles, and detect predators.