Glossary

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ESP Game(also: Extra Sensory Perception Game)

A human computation game, created by Luis von Ahn, in which two randomly paired online players are shown the same image and independently type words to describe it, earning points when their labels match. The ESP Game was designed to generate accurate, human-validated labels for…

Ecological Metaphor(also: Ecological Validity, Ecological Mapping)

A design principle in sonification and auditory display where the mapping between data and sound aligns with users' real-world sensory and cognitive experience. For example, mapping obstacle distance to pulse rate (like sonar or parking sensors), height to pitch (higher…

Embodied Cognition(also: Embodiment)

A theory in cognitive science proposing that the mind is not an isolated entity but is deeply integrated with the body's sensorimotor systems. In other words, how we think, perceive, and make decisions is shaped by our physical bodies and their interactions with the environment.…

Embodied Conversational Agent(also: ECA, Virtual Agent, Animated Agent)

A computer-generated animated character designed to interact with human users using multiple simultaneous communication channels — typically speech, eye gaze, facial expression, head and body posture, and hand gestures. ECAs are used in tutoring systems, customer-service agents,…

Embodied Interaction(also: Embodied Cognition in HCI)

An approach to human-computer interaction that emphasizes the role of the physical body in how people engage with and understand technology. Embodied interaction recognizes that cognition is not purely mental but shaped by physical experience, movement, and sensory engagement.…

Embodied participation(also: Embodied presence)

The experience of being physically present and actively engaged in a shared space through one's body or a technological proxy for it. In accessibility contexts, embodied participation refers to how technologies like telepresence robots can provide remote users with a physical…

Emulated Empathy

Emulated empathy is the design strategy, central to AI companion systems, of producing interactional cues - attentive language, affective mirroring, memory of previously shared information - that simulate an empathic relationship without the system possessing any subjective…

Engagement Detection(also: Engagement Monitoring, Engagement Recognition)

The use of sensors, computer vision, or other technologies to automatically assess whether a person is actively engaged with a task, device, or activity. Engagement detection systems typically monitor observable behaviours such as gaze direction, touch interaction patterns,…

Experiential Transcoding

An approach to web page transcoding that restructures content based on actual user behaviour rather than relying solely on source code analysis or predefined heuristics. By analysing how sighted users interact with web pages — typically through eye-tracking data — experiential…

Eye Gaze(also: Gaze, Gaze Direction, Visual Gaze)

The direction and focus of a person's eyes during visual attention, used both as a communication signal and as a measurable indicator of cognitive processing. In sign language communication, eye gaze serves critical linguistic functions including marking grammatical…

Eye Tracking(also: Eye-Tracking, Gaze Tracking)

A research methodology that uses specialized hardware (such as infrared cameras) to measure where a person is looking on a screen or in an environment, recording the sequence and duration of gaze fixations. In accessibility research, eye tracking provides objective behavioral…

Eye Tracking(also: Gaze Tracking, Eye-Tracking)

A research methodology and assistive technology that measures where a person looks (fixation points), how their gaze moves across a display (saccades), and how long they focus on specific areas (dwell time). In accessibility research, eye tracking reveals how users visually…

Eye tracking(also: Gaze tracking, Eye-gaze tracking, Eye Tracker)

A technology that measures where a person is looking on a screen or in an environment by detecting eye position and movement, typically using infrared light and cameras. In accessibility, eye tracking serves dual roles: as an assistive input method allowing people with severe…

Fitts' Law(also: Fitts Law)

A predictive model of human movement in human-computer interaction that states the time required to move to a target area is a function of the distance to the target and the size of the target. Specifically, larger and closer targets are faster to acquire than smaller and more…

Fitts' Law(also: Fitts Law)

A predictive model of human movement that describes the time required to rapidly move to a target area as a function of the distance to the target and the target's size. Formulated by psychologist Paul Fitts in 1954, the law states that larger, closer targets are faster to…

Fitts's Law(also: Fitts Law)

A predictive model of human movement that describes the time required to rapidly move to a target area as a function of the distance to the target and the size of the target. Formulated by Paul Fitts in 1954, the law states that movement time increases logarithmically as the…

Fitts's Law(also: Fitts Law, Fitts' Law)

A predictive model of human movement that describes the time required to rapidly move to a target area as a function of the distance to the target and the target's size. Smaller and more distant targets take longer to reach and are more prone to errors. In accessibility, Fitts's…

GOMS(also: Goals, Operators, Methods, and Selection rules, KLM, Keystroke-Level Model)

A family of human-computer interaction models used to predict how long it will take a user to complete a task with a given interface. GOMS stands for Goals, Operators, Methods, and Selection rules — the four components used to describe user behavior. The simplest variant, the…

Galvanic Skin Response(also: GSR, Electrodermal Activity, EDA)

A physiological measurement technique that detects changes in the electrical conductance of the skin caused by sweat gland activity. Because sweat glands are controlled by the sympathetic nervous system, GSR provides an objective indicator of emotional arousal, stress, and…

Game accessibility(also: Gaming accessibility, Accessible gaming)

The practice of designing video games and interactive entertainment so they can be played and enjoyed by people with disabilities. Game accessibility encompasses a wide range of considerations including remappable controls for motor impairments, audio cues and sonification for…

Gamification

The application of game design elements — such as points, rewards, competition, collection mechanics, and progress tracking — in non-game contexts to increase engagement and motivation. In accessibility work, gamification has been used to encourage people to contribute…

Gesture Input(also: Gesture Recognition, Gesture-Based Interaction)

An input method that uses physical movements of the body — typically hands, fingers, arms, or head — to interact with digital systems. Gesture input includes touchscreen gestures (swipes, taps, pinches), mid-air gestures detected by cameras or motion sensors, and motion gestures…

Gesture-Based Input(also: Gesture input, Gestural input, Gesture-based text entry)

An input method that interprets finger or hand movements — such as swipes, taps, and drawn paths — as commands or text characters. For people with visual impairments, gesture-based input on touchscreens offers an alternative to traditional keyboard layouts that require targeting…

Gesture-Based Interaction(also: Gesture Control, Gestural Input)

A mode of human-computer interaction where users control digital systems through hand or body movements detected by cameras or sensors, rather than through traditional input devices. In mixed reality headsets like the HoloLens 2, gesture-based interactions include touching,…

Graphical User Interface(also: GUI, WIMP Interface)

A visual interface paradigm based on windows, icons, menus, and pointer (WIMP) interaction, which became dominant in personal computing from the late 1980s onward. GUIs represented a major accessibility challenge when they replaced text-based command lines: screen readers…

Grid Recursion(also: Recursive Grid Navigation, Hierarchical Grid)

A navigation technique where a grid cell can be further subdivided into a finer sub-grid, allowing users to achieve progressively more precise positioning through successive levels of refinement. For example, a 3x3 top-level grid provides 9 positions; descending one level into a…

Grid-Based Interface(also: Grid Navigation Interface)

An interaction paradigm that divides a screen or workspace into a grid of cells, allowing users to navigate by specifying grid coordinates rather than precise pixel positions. Grid-based interfaces are particularly valuable for non-visual access because they provide a structured…

Guiard's Theory of Asymmetric Bimanual Action(also: Guiard kinematic chain model, Asymmetric bimanual action model)

Yves Guiard's 1987 model describing how the two hands typically take complementary, asymmetric roles in everyday manual tasks. The non-dominant hand sets a coarse spatial frame of reference that the dominant hand operates within, the non-dominant hand precedes the dominant hand…

Gulf of Execution

A concept from Don Norman's theory of action describing the gap between a user's intention and the actions available to achieve that goal through an interface. When the gulf of execution is large, users struggle to figure out how to operate a system to accomplish their…

Hands-Free Control(also: Hands-Free Interaction, Hands-Free Input)

Any method of operating a device or computer system that does not require the use of the hands or fingers. Hands-free control encompasses a range of input techniques including voice commands, eye tracking, head movements, sip-and-puff switches, foot controls, and EMG-based…

Haptic Device(also: Haptic Interface, Force-Feedback Device, Tactile Device)

A hardware device that provides tactile or force feedback to users, enabling them to feel virtual objects, textures, resistance, or vibrations. Haptic devices range from simple vibration motors in smartphones to sophisticated force-feedback systems like the Geomagic Touch…

Hick-Hyman Law(also: Hick's Law)

A principle from experimental psychology stating that the time it takes a person to make a decision increases logarithmically with the number of available choices. In accessibility and interface design, Hick-Hyman Law informs the practice of limiting the number of options…

Human Factors Engineering(also: Ergonomics, Human Factors)

The scientific discipline concerned with designing systems, products, and environments to be compatible with the physical and cognitive capabilities and limitations of the people who use them. In accessibility, human factors engineering applies usability methods and techniques —…

Human Interface Device(also: HID, Input Device, Peripheral)

Any device used to facilitate interaction between a human and a computer, including keyboards, mice, trackballs, joysticks, touchscreens, switches, and eye-tracking systems. The USB HID standard defines a protocol for these devices that enables plug-and-play compatibility. For…

Human-AI Collaboration(also: Human-AI Teaming, AI-Assisted Authoring)

An interaction paradigm where humans and artificial intelligence systems work together, each contributing their complementary strengths to achieve outcomes neither could produce as effectively alone. In accessibility contexts, human-AI collaboration combines AI efficiency in…

Human-AI Interaction(also: HAI, Human-AI Collaboration, AI Interaction Design)

The study and design of how people interact with artificial intelligence systems, including how AI communicates its outputs, uncertainty, and limitations to users. Key principles include making AI behavior transparent, supporting user correction of errors, acknowledging…

Human-Centered Computing(also: Human-Centred Computing, People-Centered Computing)

Human-centered computing is an approach to technology design and development that places human needs, capabilities, and experiences at the center of the design process. It emphasizes understanding the full diversity of human physical, sensory, and cognitive abilities, and…

Human-Robot Interaction(also: HRI)

The interdisciplinary field studying how humans and robots communicate, collaborate, and coexist. In accessibility contexts, HRI research explores how robots can be designed to support people with disabilities in workplaces, homes, and public spaces — including collaborative…

Human-Vehicle Interaction(also: HVI, Vehicle-pedestrian interaction)

The field studying how people communicate, negotiate, and coordinate with vehicles and their occupants — including drivers, passengers, and, increasingly, automated systems. Human-vehicle interaction encompasses internal interfaces (dashboards, voice assistants,…

Human-like trust in AI(also: Anthropomorphic trust)

The phenomenon where users develop trust in AI systems based on their human-like qualities — such as natural voice, conversational style, emotional expressiveness, and social behaviors — rather than the system's actual functional reliability. In accessibility contexts, this…

Humanoid Robot(also: Humanoid)

A robot whose physical form approximates a human body, typically with a head, torso, two arms, and (in bipedal designs) two legs. Humanoid robots are studied in accessibility research as embodied demonstrators that can present gestures, postures, and movement sequences in ways…

Imaginary Interface(also: Spatial Memory Interface, Empty-Handed Interaction)

An interaction paradigm where users interact with a virtual interface mapped to empty space or their own body, without any physical device in the interaction area. Users transfer their spatial memory of familiar device layouts (like a smartphone screen) to their palm or mid-air,…

Implicit Scoping(also: Prioritized Scoping)

A voice navigation strategy that combines the efficiency of relaxed scoping with intelligent disambiguation. In implicit scoping, the system maintains awareness of the user's current focus area and prioritizes targets based on proximity and context. When a user issues a command,…

Implicit User(also: Model User, Implied User)

A concept from semiotic engineering describing the hypothetical user that a designer envisions when creating an interface — encompassing assumptions about the user's behaviour, experience, competence, expectations, and goals. Every interface carries an implicit user embedded in…

Index of Difficulty(also: ID, Fitts ID)

The Index of Difficulty (ID) is the central quantity in Fitts' law that captures how hard a rapid aimed pointing movement is, computed as log₂(A/W + 1) in the Shannon formulation, where A is the amplitude (distance to the target) and W is the target width along the movement…

Infant-Computer Interaction(also: Baby-Computer Interaction)

The design and study of technology interfaces intended for use by infants, typically under 24 months of age. Infant-computer interaction presents unique challenges compared to other user populations because infants cannot be instructed, cannot provide explicit feedback about…

Information Rate(also: Throughput, Bandwidth)

The amount of information successfully communicated per unit of time through a communication channel or interface, measured in bits per second. In HCI and assistive technology evaluation, information rate quantifies how efficiently a user can convey commands or intentions…

Information Theory(also: Shannon Theory, Mathematical Theory of Communication)

A mathematical framework developed by Claude Shannon in 1948 for quantifying the transmission, processing, and storage of information. Central concepts include entropy (the measure of uncertainty or unpredictability in a message source), information rate (the reduction of…

Input Adaptation(also: Input Device Adaptation, Input Modality Adaptation)

The process of automatically or manually modifying an application's user interface to work with input devices or methods it was not originally designed for. Input adaptation addresses the fact that most graphical user interfaces are designed for keyboard and mouse, yet many…

Interaction metaphor

A conceptual mapping that allows users to understand and interact with a digital interface by drawing on familiar experiences or mental models. Common examples include the desktop metaphor (files, folders, trash can), direct manipulation (dragging objects), and the page metaphor…