Glossary

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Muscle Fatigue(also: Motor fatigue)

A decline in the capacity of a muscle or muscle group to generate force or sustain activity after prolonged or repeated exertion. In human-computer interaction, muscle fatigue is a central concern for input modalities requiring sustained or repetitive motion — notably mid-air…

Muscle-Computer Interface(also: MCI (Muscle-Computer Interface), EMG Interface)

An input modality in which signals generated by muscle contractions — typically recorded via surface electromyography (sEMG) sensors worn on the forearm or other muscle group — are interpreted by a computer to recognise discrete gestures or continuous control signals. Coined by…

Myoelectric Control

The use of electromyographic (EMG) signals from voluntary muscle contractions as control inputs for external devices, most commonly powered upper-limb prostheses but also exoskeletons, wheelchairs, and general computer input. Traditional myoelectric control uses direct mappings…

Neck Range of Motion(also: Cervical Range of Motion, Neck ROM)

The extent to which a person can move their head and neck through three planes of rotation: flexion and extension (nodding forward and backward), axial rotation (turning left and right), and lateral bending (tilting ear toward shoulder). Normal active neck range of motion varies…

Neurodegenerative Disease(also: Neurodegenerative Disorder, Neurodegeneration)

A category of diseases characterized by progressive loss of structure or function of neurons, including death of nerve cells. Common neurodegenerative diseases include Alzheimer's disease, Parkinson's disease, Huntington's disease, and Amyotrophic Lateral Sclerosis (ALS). These…

Non-Verbal Vocalization(also: Non-Speech Vocalization, Vocal Gesture, Non-speech Vocalisation)

A sound produced by the voice that is not a spoken word, such as a sustained vowel sound ("Ahhhhh"), hum, or other vocal noise. In assistive technology and alternative input contexts, non-verbal vocalizations can serve as continuous control signals for cursor movement or other…

Nontraditional Assistive Technologies(also: NTATs, Nontraditional Input Technologies)

Input technologies that use physiological signals rather than physical movement to control computers, providing access for people who cannot use traditional devices like keyboards, mice, or even eye-tracking systems. NTATs include brain-computer interfaces (using EEG or fNIR),…

Oligodactyly

A congenital condition in which a person is born with fewer than the typical number of fingers or toes. The condition varies widely in presentation — some individuals may have fewer digits on one hand or both, and the remaining digits may differ in size, strength, or dexterity.…

On-Screen Keyboard(also: Virtual Keyboard, Software Keyboard, OSK)

A software application that displays a visual representation of a keyboard on the computer screen, allowing users to type by selecting keys with a pointing device, head tracker, eye gaze system, or switch. On-screen keyboards are essential assistive technology for people who…

One-Handed Input(also: Single-Handed Operation, One-Handed Operation)

One-handed input refers to interaction techniques and interface designs that can be operated using a single hand, accommodating users who have limited use of one limb due to amputation, hemiplegia, stroke, cerebral palsy, or other physical conditions. One-handed input methods…

Overshoot(also: Cursor Overshoot, Target Overshoot)

In pointing device interaction, the phenomenon where the cursor travels beyond the intended target before the user can stop it, requiring corrective movements back toward the target. Overshoot is measured as the maximum distance traveled beyond the target as a percentage of the…

Paraplegia

A condition resulting from injury to the thoracic, lumbar, or sacral segments of the spinal cord, causing partial or complete loss of motor function and sensation in the legs, pelvis, and trunk while arm and hand function is preserved. People with paraplegia can typically use…

Parkinsonian Tremor(also: Rest Tremor, Parkinson Tremor)

Parkinsonian tremor is an involuntary, rhythmic shaking that occurs primarily at rest and is associated with Parkinson's disease. It is caused by the reciprocal activation of antagonistic muscle groups and typically has a frequency of 4-6 Hz with a harmonic frequency…

Peak Velocity

The maximum speed reached by a cursor or limb during a directed movement toward a target. In human-computer interaction research, peak velocity is a key metric for understanding pointing performance, typically occurring in the first quarter of a movement. Peak velocity decreases…

Pen Input(also: Stylus Input, Pen-Based Input)

An input method using a pen or stylus to interact with a computing device, typically through direct manipulation on a touchscreen or digitizer. Pen input offers advantages for users with certain motor impairments: compared to mice, pens allow users to leverage hand-eye…

Peripheral Neuropathy(also: Neuropathy)

Peripheral neuropathy is a condition resulting from damage to the peripheral nerves, which carry signals between the brain, spinal cord, and the rest of the body. Symptoms typically include numbness, tingling, weakness, and pain, most commonly in the hands and feet. For…

Pie Menu(also: Radial Menu, Circular Menu)

A pie menu is a circular or ring-shaped menu interface in which command options are arranged radially around a central point, allowing selection by moving the cursor or making a directional gesture toward the desired item. Unlike linear drop-down menus, pie menus leverage…

Point-and-Click(also: Point and Click, Click Target)

A fundamental interaction paradigm in graphical user interfaces where the user moves a cursor to a target on screen and activates it by pressing a button on a pointing device such as a mouse or trackpad. Point-and-click tasks are central to GUI-based computing but present…

Pointer Speed(also: Mouse Gain, Cursor Speed, Mouse Speed)

An operating system setting that controls how far the cursor moves on screen relative to physical movement of the mouse or pointing device. Higher pointer speed (gain) means less physical movement is required to traverse the screen, while lower speed provides finer control but…

Pointing(also: Pointing Performance, Mouse Pointing, Cursor Pointing)

The act of moving a cursor or pointer to indicate a specific location on screen, typically to select, activate, or interact with an interface element. Pointing is a fundamental computer interaction that can be challenging for individuals with motor impairments, tremors, limited…

Pointing Device(also: Pointer Device, Input Device)

Any hardware device used to control the movement of a cursor or pointer on a computer screen, enabling users to select, click, drag, and interact with interface elements. Common pointing devices include the mouse, trackball, trackpad, touchscreen, stylus, joystick, head-tracking…

Pointing Device Gain(also: Control-Display Gain, Mouse Sensitivity, Pointer Speed)

The ratio between the movement of a physical input device (such as a mouse or trackball) and the resulting movement of the cursor on screen, typically measured in pixels per inch of device movement. Higher gain means the cursor moves further for a given physical movement. In…

Predictive Cursor(also: Anticipatory Cursor, Offset Cursor)

A cursor display technique designed to compensate for the delays inherent in speech-based or other high-latency input methods. A predictive cursor shows an indicator ahead of the actual cursor position, offset by the estimated distance the cursor will travel during the input…

Programming Accessibility(also: Accessible Programming, Accessible IDE)

The practice of making software development tools, environments, and workflows usable by programmers with disabilities. Programming presents unique accessibility challenges beyond general computer use: code requires precise typing of special characters and symbols, specific…

Range of Motion(also: ROM)

The full extent of movement possible at a joint, measured in degrees of rotation or linear distance. Range of motion is a fundamental clinical measurement used by occupational and physical therapists to assess hand, wrist, elbow, and shoulder function. In accessibility contexts,…

Remote Desktop Software(also: Remote Access Software, Remote Control Software)

Software that allows a user to access and control one computer from another device over a network, displaying the remote computer's screen and relaying input commands. In accessibility contexts, remote desktop software serves as an unexpected but powerful assistive technology…

Scanning interface(also: Switch scanning, Single-switch access)

An interaction method in which items on a screen are sequentially highlighted one at a time (or in groups), and the user activates a switch to select the currently highlighted item. Scanning interfaces provide computer access for individuals with severe motor impairments who can…

Segmentation Problem(also: Stroke Segmentation, Input Segmentation, Gesture Segmentation)

The segmentation problem in text entry and gesture recognition refers to the challenge of determining where one input unit (such as a letter, word, or gesture) ends and the next begins when there is no explicit delimiter between successive inputs. For stylus-based systems,…

Sensory-Motor Processing(also: Sensorimotor Processing, Sensorimotor Integration)

Sensory-motor processing refers to the brain's ability to receive sensory input (visual, auditory, tactile, proprioceptive) and coordinate appropriate motor responses. This includes fine motor control for tasks like typing and mouse manipulation, as well as the integration of…

Single Switch(also: Single Switch Access, One Switch)

An assistive technology input device that provides a single binary action — on or off — enabling people with severe motor impairments to interact with computers and communication devices. Switches can be activated by virtually any reliable voluntary movement, including a blink,…

Single-Switch Access(also: One-switch access, Single switch scanning)

An input method that allows users to control a computer, AAC device, or other technology using only one switch or button. Users with severe motor impairments who cannot operate a keyboard, mouse, or touchscreen can use various switch types—including buttons pressed by hand,…

Sip-and-Puff(also: Sip and Puff Switch, Pneumatic Switch)

An assistive technology input device that detects air pressure changes from a user sipping (inhaling) or puffing (exhaling) through a straw or tube to generate control signals. Sip-and-puff systems are primarily used by people with severe motor impairments, particularly those…

Slips(also: Slip Errors, Selection Slips)

Errors that occur when a user intends to click on a target but the cursor moves off the target before the mouse button is released, resulting in a missed selection. Slips are particularly common among older adults and people with motor impairments due to difficulties with fine…

Spastic Diplegia(also: Diplegic Cerebral Palsy)

A form of cerebral palsy characterised by muscle stiffness (spasticity) that primarily affects the lower limbs, though the upper limbs may also be mildly affected. It is one of the most common types of cerebral palsy. People with spastic diplegia may walk independently, use…

Spastic Triplegia(also: Triplegic Cerebral Palsy)

A form of cerebral palsy in which three limbs are affected by spasticity (muscle stiffness), typically both legs and one arm. This condition presents unique challenges for assistive technology use because the individual has limited function in three limbs while retaining…

Speech-Based Cursor Control(also: Voice Cursor Control, Speech-Driven Pointing)

A method of controlling a computer's pointing cursor using spoken voice commands rather than a mouse, trackpad, or other physical pointing device. Users speak directional commands (such as "move left," "move up") to start cursor movement and a stop command to halt it, then issue…

Speech-Based Cursor Movement(also: Voice-Controlled Cursor, Voice Cursor Control)

A technique for moving the on-screen cursor using voice commands rather than physical manipulation of a pointing device. Speech-based cursor movement systems typically use one of two approaches: discrete specification, where the user speaks a command to jump the cursor to a…

Speed-Accuracy Tradeoff(also: Speed-Accuracy Trade-off, SAT)

A fundamental principle of human motor control where increased movement speed leads to decreased accuracy, and vice versa. Users can choose to move quickly and accept more errors, or move slowly and carefully to minimize mistakes. In accessibility contexts, the speed-accuracy…

Spinal Cord Injury(also: SCI)

Damage to the spinal cord that results in temporary or permanent changes in motor function, sensation, or autonomic function below the level of injury. Depending on the location and severity, spinal cord injuries can cause paraplegia (lower body paralysis) or…

Stance-Control Orthosis(also: Stance-control KAFO, SCO, Stance-control knee-ankle-foot orthosis)

A class of knee-ankle-foot orthoses that lock the knee during the stance (weight-bearing) phase of gait to prevent buckling, but unlock it during the swing phase to allow natural knee flexion. Stance-control devices detect gait phase through joint-angle sensors,…

Steady Tapping

The ability to place a finger on a touchscreen target and hold it still long enough for the system to register a deliberate tap, as opposed to the unintentional movements caused by hand tremor. For users with motor impairments, maintaining a steady tap is a significant challenge…

Stepwise pointing(also: Recursive target acquisition, Tile-based pointing)

A mouse emulation technique in which the screen is divided into a grid of tiles, the user selects a tile to zoom into it, the tile subdivides into smaller subtiles, and this process repeats until the desired screen location is reached at pixel-level precision. Stepwise pointing…

Submovement(also: Movement Component, Movement Segment)

A discrete component of a larger aimed movement, separated from other submovements by pauses or changes in velocity. According to the Optimized Submovement Model from motor performance theory, a rapid aimed movement such as moving a cursor to a target consists of an initial…

Switch Access(also: Switch Control, Switch Scanning)

A method of computer and device interaction that uses one or more switches as input devices, designed for people who cannot use standard keyboards, mice, or touchscreens due to motor impairments. Switch access is built into major operating systems (iOS Switch Control, Android…

Switch Scanning(also: Scanning Mode, Auto Scanning)

An input method for assistive technology where options are sequentially highlighted (scanned) and the user activates a single switch to select the currently highlighted item. This enables people with severe motor disabilities to access computers, communication devices, and other…

Switch Scanning(also: Switch Access, Scanning Input)

An alternative input method in which items on a screen are sequentially highlighted and the user activates a switch to select the desired item when it is highlighted. Switch scanning is used by people with significant motor impairments who cannot use direct touch, a mouse, or a…

Target Expansion(also: Expanding Targets, Dynamic Target Sizing)

An interaction technique where clickable interface elements dynamically grow in size as the cursor approaches, making them easier to select while conserving screen space when not being targeted. Research shows target expansion can reduce selection times by up to 14% and error…

Target Selection(also: Target Acquisition, Pointing)

The fundamental interaction task of moving a cursor or pointer to a specific location on screen and confirming selection, such as clicking a button or link. Target selection difficulty is affected by target size, distance to target, and user motor abilities—relationships…

Target Size(also: Touch Target Size, Click Target Size, Hit Area)

The physical dimensions of an interactive element on screen — such as a link, button, or checkbox — that a user must point to and activate. Adequate target size is critical for users with motor impairments, tremor, or limited dexterity, as small targets require greater precision…

Target acquisition(also: Target selection, Pointing task)

The process of moving a pointer or input device to a specific on-screen element and selecting it, such as tapping an icon, clicking a button, or choosing a menu item. Target acquisition is a fundamental interaction in graphical user interfaces, and its difficulty is influenced…