Glossary

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Force-sensitive resistor(also: FSR, Pressure sensor)

An electronic sensor whose electrical resistance changes in response to applied physical pressure, enabling detection of both the presence and intensity of touch or force. In accessibility applications, force-sensitive resistors offer advantages over capacitive touchscreens…

Form Factor(also: Device Form Factor, Handset Form Factor)

Form factor refers to the overall physical size, shape, weight, and mechanical configuration of a device — for mobile phones this includes distinctions like candy-bar, clamshell (flip), slide-out keyboard, foldable, and modern all-touch slab. Form factor has direct accessibility…

Fractionation(also: Finger Fractionation, Finger Independence)

The ability to move individual fingers independently of one another, a key measure of fine motor control assessed in stroke rehabilitation. After a stroke, patients often lose fractionation, meaning that attempting to move one finger causes involuntary coupled movement in…

Freehand Gesture Interaction(also: Hand Tracking Interaction, Controller-Free Interaction)

An input method for virtual and mixed reality systems that uses camera-based hand tracking to detect and interpret natural hand movements without requiring physical controllers. Freehand gestures such as pinching, grasping, pointing, and swiping are increasingly the default…

Functional Near-Infrared Imaging(also: fNIR, fNIRS, Functional Near-Infrared Spectroscopy)

A neuroimaging technique that measures brain activity by detecting changes in oxygenated blood volume using near-infrared light transmitted through the skull. In accessibility contexts, fNIR enables brain-computer interfaces that allow people with severe motor disabilities to…

Gait(also: Walking Pattern, Locomotion Pattern)

The pattern of movement during walking, characterized by measurable parameters including walking velocity, cadence (steps per minute), step length, stride length, step time, cycle time, and swing time. Gait analysis is important in accessibility and rehabilitation because many…

Gaze Interaction(also: Gaze-Based Interaction, Gaze Input, Eye Gaze Control)

Gaze interaction is a method of controlling computers and devices by tracking where a person is looking on the screen. Using eye-tracking technology, the system detects the user's point of gaze and translates it into cursor movement or selection actions, often combined with…

Gestural Interaction(also: Gesture-Based Interaction)

A mode of human-computer interaction in which users control systems through movements of the body — hands, arms, head, eyes, or whole body — captured by sensors such as accelerometers, cameras, IMUs, or depth sensors. Gestural interaction supports hands-free or low-force control…

Gesture Elicitation(also: User-Defined Gestures)

Gesture elicitation is a participatory design method where end users are asked to invent gestures for a set of device functions, rather than having gestures predetermined by designers or engineers. Participants are shown the effect of an action (such as zooming in) and asked to…

Gesture Interaction(also: Gesture-based interaction, Gestural interfaces)

An input modality in which users control digital systems through hand, arm, or body movements detected by cameras, depth sensors, IMUs, or wearable devices rather than through traditional keyboards, pointing devices, or touchscreens. Gesture interaction underpins many augmented…

Gesture Recognition Threshold(also: Activation Threshold, Gesture Detection Threshold)

The predefined parameters that a gesture recognition system uses to determine whether a user's hand movement constitutes a valid gesture input. These thresholds specify requirements such as the exact finger positions, distances between fingertips, hand openness levels, and…

Gesture-based interaction(also: Gestural interface, Touchless interaction)

An interaction modality where users control technology through body movements, hand gestures, or postures detected by sensors such as depth cameras, rather than through traditional input devices like keyboards, mice, or touchscreens. Gesture-based interaction can benefit people…

Ghost Cursor(also: Phantom Cursor, Proxy Cursor)

A visual indicator displayed on screen that shows a potential cursor position, used in speech-based and alternative cursor movement systems. Multiple ghost cursors can be displayed simultaneously, typically aligned in a row or column, allowing users to quickly specify an…

Goal Crossing(also: Crossing-Based Input, Crossing Interface)

An input technique where users select targets by moving through a boundary line rather than clicking within a target area. Research shows goal crossing can improve input performance for people with motor impairments by reducing the precision demands of target acquisition—users…

Gorilla Arm Syndrome(also: Gorilla Arm, Gorilla Arm Effect)

Fatigue, pain, and discomfort in the arms and shoulders caused by prolonged use of interfaces that require sustained arm elevation without support. The term originates from early touchscreen computing and has become particularly relevant in virtual and mixed reality, where users…

Gravity Well(also: Target Attraction, Sticky Targets, Snap-to-Target)

An interaction filtering technique that warps the cursor space around interactive targets (such as buttons or links), creating attractive basins that pull the cursor toward the nearest target. This makes it easier for users with motor impairments to select small or distant…

Grid-Based Cursor Control(also: Grid-Based Navigation, Grid Overlay Navigation)

A hands-free cursor positioning technique that overlays a numbered grid on the screen, allowing users to select a cell by voice command or other input to recursively zoom into smaller screen regions until the desired target is reached. Grid-based approaches reduce the vocabulary…

Grid-Based Navigation(also: Grid Navigation, Grid Cursor Control)

A speech-controlled cursor positioning technique that divides the screen into numbered regions, allowing users to select progressively smaller areas by speaking numbers until the cursor reaches the target location. This alternative input method enables people with upper-body…

Hands-Free Interface(also: Hands-Free Computing, Hands-Free Input)

A hands-free interface is a computer interaction system that does not require the use of hands or fingers, enabling users to control software through alternative input channels such as head movements, eye gaze, voice commands, foot pedals, or breath-controlled switches. These…

Head Control(also: Head-Controlled Interface, Head Mouse, Head Pointer)

An alternative computer input device that translates head movements into cursor movements on screen, enabling people who cannot use their hands or arms to operate a computer. Head control systems typically use ultrasonic sensors, infrared tracking, or camera-based systems to…

Head Pointer(also: Head Mouse, Head Tracking Device)

An assistive technology input device that translates head movements into cursor movements on screen, allowing people who cannot use their hands or arms to control a computer. Head pointers can be physical devices (a stick or stylus mounted on a headband used to press keys) or…

Head Pointing(also: Head-Controlled Pointing, Head Mouse)

Head pointing is an alternative input method that maps head movements to cursor position on a computer screen, enabling hands-free mouse control. The user moves their head to direct the cursor, with the system translating head orientation or position into screen coordinates.…

Head Wand(also: Head Pointer, Head Stick, Mouth Stick)

A head wand is an assistive input device consisting of a pointer attached to a headband or held in the mouth, allowing people with limited or no hand and arm function to operate a keyboard, touchscreen, or other controls using head movements. Head wands are commonly used by…

Head-based Pointing(also: Head Tracking, Head Mouse, Head-controlled Input)

An alternative input method that allows users to control an on-screen cursor by moving their head, typically tracked via a camera, infrared sensor, or inertial measurement unit. Head-based pointing is particularly valuable for people with motor impairments who cannot use…

Heisenberg Effect(also: Heisenberg Problem)

In human-computer interaction, a spatial interaction problem where the act of making a selection disrupts the positional accuracy of the cursor or pointer. In virtual reality freehand gesture contexts, the Heisenberg effect occurs when the physical movement required to confirm a…

Input Exertion(also: Input Effort, Interaction Cost)

The physical and cognitive effort required to provide input to a digital system, including keystrokes, mouse movements, taps, and voice commands. For people with motor impairments, input exertion is a critical accessibility concern because even small inefficiencies — such as…

Integrated Control System(also: Integrated Control)

An assistive technology approach where a single input device serves multiple control functions, such as wheelchair navigation, mouse cursor control, and text entry. Integrated control systems reduce the number of separate devices a person with a disability must manage, lowering…

Isometric Gesture(also: Isometric Contraction Gesture)

An isometric gesture is a gesture in which a person activates their muscles without producing visible movement — the body position remains static while muscle tension changes. This contrasts with isotonic gestures, where visible hand or arm movement occurs over time. Isometric…

Joystick(also: Adaptive Joystick)

A joystick is an input device with a lever that tilts in multiple directions to control cursor movement on screen, used as an alternative pointing device by people with motor impairments who have difficulty using a standard mouse. Adaptive joysticks come in various forms — some…

Key Acceptance Delay(also: Acceptance Delay, Key Debounce)

A keyboard accessibility setting that requires a key to be held down for a specified minimum duration before it is registered as a deliberate press. Keys released before the delay period expires are ignored, filtering out brief accidental touches. Key acceptance delay is the…

Key Remapping(also: Key Rebinding, Control Remapping, Custom Key Bindings)

The ability to reassign keyboard controls to different keys than the software defaults. Key remapping is essential for users with motor disabilities who may only be able to reach certain areas of the keyboard, use one hand, or have limited range of motion. For example, a…

Keyguard(also: Keyboard Guard, Key Guard)

A rigid cover that fits over a keyboard with holes aligned to each key, allowing users with motor impairments to rest their hands on the surface without accidentally pressing keys. Keyguards help people who have imprecise motor control, tremors, or involuntary movements to type…

Knee-Ankle-Foot Orthosis(also: KAFO)

A lower-limb orthosis that spans the knee, ankle, and foot to provide weight-bearing support and prevent knee buckling or hyperextension in people with significant leg weakness or paralysis - commonly due to stroke, spinal cord injury, post-polio syndrome, or muscular dystrophy.…

Linear Scanning(also: Row-column scanning, Automatic scanning)

An input method for AAC devices and on-screen keyboards where selections are highlighted sequentially, typically row by row and then item by item, allowing users with severe motor impairments to select options using a single switch. The system automatically moves through options…

Locomotion Technique(also: VR Locomotion, Virtual Travel Technique)

A locomotion technique is a method for navigating or moving through a virtual environment in virtual reality (VR). Because physical space is limited and many users are seated, locomotion techniques simulate travel without requiring real-world walking. Common approaches include…

Manual Dexterity(also: Fine Motor Skills, Hand Dexterity)

The ability to use hands and fingers to perform precise, coordinated movements. Reduced manual dexterity can result from conditions such as arthritis, neurological disorders, injuries, or aging, and affects the ability to use keyboards, mice, touchscreens, and other input…

Manual Muscle Testing(also: MMT, Muscle Strength Testing)

Manual muscle testing (MMT) is a clinical assessment technique used by occupational therapists, physiotherapists, and other healthcare professionals to evaluate the strength of individual muscles or muscle groups. The examiner applies resistance to the patient's movement and…

Midas Touch Problem(also: Midas Touch Effect)

The Midas Touch problem is a well-known challenge in gaze-based and dwell-time-based computer interfaces where everything the user looks at or pauses the cursor over is interpreted as a selection command. Named after King Midas who turned everything he touched to gold, the…

Mobility Disability(also: Mobility Impairment, Physical Mobility Limitation)

A disability that affects a person's ability to move freely, including walking, climbing stairs, maintaining balance, or using fine motor skills. Mobility disabilities may result from conditions such as spinal cord injury, cerebral palsy, multiple sclerosis, amputation,…

Motion-based game accessibility(also: Movement game accessibility, Exergame accessibility)

The design and adaptation of video games that use physical movement as the primary input — such as Kinect, Wii, and VR games — to be playable by people with motor impairments including wheelchair users. Commercial motion-based games typically assume standing play and full-body…

Motor Accessibility(also: Physical Accessibility, Motor Impairment Accessibility)

Motor accessibility refers to the design of digital systems and interfaces to be operable by people with physical disabilities affecting movement, strength, coordination, or fine motor control. Relevant conditions include cerebral palsy, muscular dystrophy, spinal cord injury,…

Motor Function Time(also: Motor Response Time, Motor Cycle Time)

The time required to execute a physical action such as pressing or releasing a key, clicking a mouse button, or moving a pointing device. In the Model Human Processor, motor function time for able-bodied users averages approximately 70 milliseconds per action. For motor-impaired…

Motor Recovery(also: Motor Rehabilitation, Motor Function Recovery)

The process of regaining voluntary movement control and physical function after neurological injury such as stroke, traumatic brain injury, or spinal cord damage. Motor recovery involves reorganization of neural pathways through cortical plasticity, where undamaged areas of the…

Motor Skill(also: Motor Skills, Gross Motor Skill, Fine Motor Skill)

A motor skill is a learned ability to produce a coordinated movement of muscles to achieve an outcome, ranging from gross-motor actions like walking, jumping, and balancing to fine-motor actions like handwriting, buttoning a shirt, or manipulating a stylus. Motor skills strongly…

Mouse Alternative(also: Alternative Pointing Device, Mouse Replacement)

A mouse alternative is any input device or technique that lets a user perform pointer-control tasks — moving a cursor, clicking, dragging, selecting — without using a conventional mouse. For people with motor impairments, mouse alternatives include trackballs, head-pointer and…

Mouse Emulation(also: Mouse Simulation, Virtual Mouse)

Software or hardware that simulates mouse pointer movement, clicks, and other mouse actions using alternative input methods such as head tracking, eye gaze, joysticks, switch scanning, keyboard commands, or biosignal interfaces. Mouse emulation enables people who cannot use a…

Mouth Interface(also: Mouth-operated interface, Mouth-based input)

An input modality that uses mouth movements - tongue position, cheek puffs, jaw motion, lip gestures, breath, or sip-and-puff - to control a computer, wheelchair, or XR system. Mouth interfaces serve people with limited upper-limb mobility (e.g., spinal cord injury, muscular…

Mouth Joystick(also: Lip Joystick, Mouth-Operated Joystick)

An assistive input device controlled by the user's mouth, lips, or tongue that functions as a pointer or gamepad joystick. The user moves a small stick held between the lips to direct cursor or on-screen movement; selection is typically triggered by a sip-and-puff switch, chin…

Movement Disorder(also: Motor Disorder)

A group of neurological conditions that affect the speed, fluency, quality, and ease of movement. Movement disorders can cause excessive or reduced movement that may or may not be voluntary. Common types include Parkinson's disease, essential tremor, dystonia, and Huntington's…

Multimodal Input(also: Multimodal Interaction, Multi-modal Input)

An interaction approach that allows users to communicate with computing devices or systems through multiple input channels — such as touch, voice, eye gaze, head movement, facial expressions, hand gestures, brain-computer interfaces, and biometrics — either simultaneously or…