Glossary
Binocular Cues
Depth cues, such as retinal disparity, that depend on the use of both eyes.
Example:
When trying to thread a needle, you naturally use both eyes to leverage binocular cues for precise depth judgment.
Brightness Constancy
A type of perceptual constancy that allows us to perceive an object as having a consistent level of brightness even as the illumination changes.
Example:
A white shirt appears equally white whether you're in a brightly lit room or a dimly lit hallway, due to brightness constancy.
Closure
A Gestalt grouping principle where we tend to fill in gaps to create a complete, whole object.
Example:
If you see a drawing of a circle with a small section missing, your brain automatically fills in the gap to perceive a complete circle, illustrating closure.
Color Constancy
A type of perceptual constancy that allows us to perceive the consistent color of an object even under different lighting conditions.
Example:
A red apple still looks red whether you see it in bright sunlight or dim indoor light, thanks to color constancy.
Connectedness
A Gestalt grouping principle where we perceive uniform and linked items as a single unit.
Example:
A string of Christmas lights, even if individual bulbs are spaced out, is perceived as one continuous decoration due to connectedness.
Continuity
A Gestalt grouping principle where we perceive smooth, continuous patterns rather than discontinuous ones.
Example:
Even if a tree branch partially blocks a road, you still perceive the road as a continuous path, thanks to the principle of continuity.
Depth Perception
The ability to see objects in three dimensions, even though the images that strike the retina are two-dimensional, allowing us to judge distance.
Example:
When you successfully catch a ball thrown to you, your depth perception allowed you to accurately judge its distance and trajectory.
Figure-Ground
The Gestalt principle that states we organize our visual field into objects (figures) that stand out from their surroundings (ground).
Example:
In a crowded room, focusing on your friend's voice while tuning out the background chatter is an auditory example of figure-ground organization.
Gestalt Principles
A set of principles describing how we organize our sensations into meaningful wholes or 'gestalts,' emphasizing that the whole is greater than the sum of its parts.
Example:
When you look at a scattered group of dots and automatically see a dog, you're applying Gestalt Principles to organize the visual information.
Interposition
A monocular depth cue where if one object partially blocks our view of another, we perceive it as closer.
Example:
When a book on your desk covers part of your laptop, you know the book is closer because of interposition.
Light and Shadow
A monocular depth cue where shading and light patterns provide information about the three-dimensional form and depth of objects.
Example:
A drawing can create the illusion of a sphere rather than a flat circle by using strategic light and shadow to suggest curvature.
Linear Perspective
A monocular depth cue where parallel lines appear to converge in the distance.
Example:
Standing on a long, straight road, you notice the edges of the road seem to meet at a point far away, an illusion created by linear perspective.
Monocular Cues
Depth cues, such as interposition or linear perspective, that are available to either eye alone.
Example:
An artist uses monocular cues like relative size and linear perspective to create the illusion of depth on a flat canvas.
Motion Perception
The process by which we infer the speed and direction of moving objects.
Example:
When watching a car drive by, your brain uses cues like changing size and position to achieve motion perception.
Perception
The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
Example:
Seeing a collection of lines and colors and recognizing it as your friend's face is an act of perception.
Perceptual Adaptation
The ability to adjust to an artificially displaced or even inverted visual field.
Example:
When you first put on a new pair of glasses with a slightly different prescription, your vision might feel off, but your brain quickly undergoes perceptual adaptation to adjust.
Perceptual Constancy (Object Constancy)
The tendency to perceive familiar objects as having consistent color, brightness, shape, and size, even as illumination, distance, or angle changes.
Example:
Even as a friend walks away from you, you don't perceive them as shrinking; your brain maintains perceptual constancy of their size.
Phi Phenomenon
An illusion of movement created when two or more adjacent lights blink on and off in quick succession.
Example:
The flashing lights on a theater marquee that appear to move around the sign are an example of the phi phenomenon.
Proximity
A Gestalt grouping principle where we tend to group nearby figures together.
Example:
When you see three people standing very close together, you assume they are a single group or conversation, demonstrating the principle of proximity.
Relative Height
A monocular depth cue where objects higher in our field of vision are perceived as farther away.
Example:
Looking at a landscape, you perceive distant mountains as being higher on the horizon than closer trees, illustrating relative height.
Relative Motion/Motion Parallax
A monocular depth cue where as we move, objects that are closer appear to move faster and in the opposite direction, while objects farther away appear to move slower or in the same direction.
Example:
While riding in a car, nearby telephone poles seem to whiz by quickly, but distant mountains appear to move slowly, demonstrating relative motion.
Relative Size
A monocular depth cue where if two objects are known to be similar in size, the one that casts a smaller retinal image is perceived as farther away.
Example:
You know two cars are roughly the same size, so the one that appears smaller in your vision is perceived as being farther down the road due to relative size.
Retinal Disparity
A binocular depth cue referring to the difference between the images seen by the left and right eyes; the brain uses this difference to compute distance.
Example:
When you hold your finger close to your nose and alternate closing each eye, your finger appears to jump because of the significant retinal disparity.
Sensation
The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
Example:
When light waves hit your retina, that's sensation – the raw data your eyes are collecting.
Shape Constancy
A type of perceptual constancy that allows us to perceive the consistent shape of an object even when its retinal image changes due to viewing angle.
Example:
A door still appears rectangular even when it's ajar and its image on your retina is a trapezoid, thanks to shape constancy.
Similarity
A Gestalt grouping principle where we tend to group similar figures together.
Example:
In a marching band, you perceive all the trumpeters as one group because of their similarity in instruments and uniforms.
Size Constancy
A type of perceptual constancy that allows us to perceive the consistent size of an object even when its distance from us changes, altering its retinal image size.
Example:
As an airplane flies overhead and gets farther away, you still perceive it as a large aircraft, not a tiny toy, because of size constancy.
Stroboscopic Movement
The illusion of movement created when a series of still images are presented rapidly in succession, with slight variations between them.
Example:
A flip book creates the illusion of a character running through stroboscopic movement.