Glossary

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Parallax(also: Visual Parallax, Binocular Parallax)

Parallax is the apparent displacement or difference in position of an object when viewed from two different vantage points. In human vision, binocular parallax — the slight difference between the images seen by each eye due to their spatial separation — is a primary cue for…

Perceptual Bandwidth(also: Sensory Bandwidth, Information Bandwidth)

Perceptual bandwidth refers to the rate at which a sensory channel can transmit information to the brain. In accessibility contexts, the concept highlights the fundamental asymmetry between vision and hearing: vision has extremely high bandwidth, allowing a sighted person to…

Perceptual Cycle(also: Perceptual Response Time, Perceptual Processing)

In the Model Human Processor framework, the perceptual cycle is the time required for a person to perceive and register a stimulus from their environment, such as seeing a visual change on screen. The perceptual cycle time for both able-bodied and motor-impaired users is…

Perceptual Integration(also: Perceptual Binding)

The process by which the brain combines information arriving through different sensory channels — vision, hearing, touch, proprioception — into a single coherent percept of an object or event. Perceptual integration depends on temporal synchrony (cues arriving within roughly 100…

Perceptual Learning(also: Visual Perceptual Learning, PL)

A long-studied phenomenon in vision science in which repeated exposure to, or training on, specific perceptual features — color, orientation, spatial location, shape — produces durable improvements in a person’s ability to detect and discriminate those features. Perceptual…

Perceptual Span(also: Reading Span, Visual Span)

The area of text around a fixation point from which useful information can be extracted during reading. Research using eye-tracking has shown that skilled deaf readers have a larger perceptual span than hearing readers — up to 18 letter spaces compared to 14 for hearing readers…

Peripheral Awareness(also: Peripheral Perception, Ambient Awareness)

The innate ability to unconsciously maintain and constantly update a sense of one's social and physical surroundings without actively directing attention to them. In accessibility contexts, peripheral awareness is critical for social interaction, as sighted people effortlessly…

Phantom Sensation(also: Phantom Vibration, Vibrotactile Illusion)

A phantom sensation is a perceptual illusion in which two vibrotactile actuators stimulating the skin simultaneously create the feeling of a single vibration at a point between them. By varying the amplitude and frequency of each actuator, the perceived location of the phantom…

Point-of-Gaze(also: POG, Gaze Point, Point of Regard)

Point-of-gaze is the location on a display, scene, or object at which a user's eye is currently fixating, typically reported by an eye tracker as a stream of (x, y) screen coordinates sampled at rates between 30 and several hundred hertz. Raw point-of-gaze data is noisy and…

Presence(also: Virtual Presence, Sense of Presence)

The subjective sense of being in a virtual environment, often described as the feeling of "being there" rather than simply observing a digital display. Presence is a central construct in VR research and is influenced by sensory fidelity, interaction naturalness, avatar…

Proprioception(also: Proprioceptive Sense, Body Position Sense)

The body's ability to sense its own position, movement, and orientation in space without relying on vision. Proprioceptive information comes from sensory receptors in muscles, tendons, and joints that detect stretch, tension, and pressure. For people who are blind or have low…

Pseudo-Attraction Force

A haptic illusion technique that creates the sensation of being pulled or pushed in a specific direction by exploiting the nonlinear relationship between physical and perceived acceleration. The technique uses asymmetric oscillation: a strong, brief acceleration in the intended…

Psychophysics

Psychophysics is the scientific study of the quantitative relationship between physical stimuli and the sensations and perceptions they produce. Founded in the 19th century, it uses rigorous experimental methods to measure how humans detect, discriminate, and scale sensory…

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