Glossary

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Intermediated Technology Use(also: Intermediated Interaction, Assisted Technology Use)

A pattern of technology interaction where a person accesses technology through the assistance of another person (an intermediary) rather than using it directly themselves. This occurs when barriers such as cost, literacy, disability, or lack of access prevent direct use. Common…

Iterative Crowdsourcing(also: Iterative Human Computation, Multi-Round Crowdsourcing)

A human computation workflow in which multiple rounds of crowd workers build iteratively upon each other's responses to collectively achieve higher quality results than any individual worker could produce alone. In each iteration, workers are shown the previous round's outputs…

Keystroke-Level Model(also: KLM)

A simplified predictive model from human-computer interaction research, originally developed by Card, Moran, and Newell, that estimates task completion time by decomposing user interactions into elementary operations such as keystrokes, pointing movements, mouse clicks, and…

Learning by Doing(also: Incidental Learning, Learning-While-Doing)

Learning by doing is a pedagogical and interface design principle in which skills are acquired through the process of performing tasks rather than through separate, explicit instruction. In human-computer interaction, interfaces designed around this principle enable users to…

Linear Interaction(also: Sequential Interaction, Single-path Navigation)

An interface design pattern in which users engage with only one screen or task at a time, following a single sequential path rather than managing multiple overlapping windows, tabs, or concurrent contexts. Linear interaction reduces cognitive load by eliminating the need to…

Logical Control(also: Indirect Control)

An interaction paradigm where the user accesses specific functions supported by an application indirectly, typically by selecting from a presented set of options rather than performing the action directly. Examples include scanning through a menu of commands, using keyboard…

Low Bandwidth Input(also: Limited Input, Reduced Bandwidth Input)

A category of human-computer interaction where the user can only produce a very small number of distinct signals — typically one to four — when communicating with a computer. Low bandwidth input characterizes users with severe motor and speech impairments, such as those with…

Machine Teaching(also: Interactive Machine Teaching)

A paradigm in human-computer interaction where non-expert users guide the training of machine learning models through interactive feedback, such as providing examples, labels, or corrections. Unlike traditional machine learning where data scientists prepare datasets and tune…

Mental Workload(also: Cognitive Load, Cognitive Workload)

The amount of cognitive effort and mental resources required to complete a task. In accessibility contexts, mental workload is an important measure of how demanding an interface is to use — an interface may be technically functional but impose excessive cognitive burden on users…

Menu Selection(also: Menu Navigation, Menu Selection Task)

A fundamental computer interaction task in which a user chooses an option from a set of items presented in a menu structure, typically involving locating the target item, moving the cursor to it, and clicking to select. Menu selection performance is commonly measured by task…

Metacommunication(also: Designer-User Metacommunication)

In semiotic engineering, metacommunication refers to the overarching communication that takes place between a software designer and a user through the medium of the computer interface. The interface acts as the designer's deputy, conveying messages about what the system does,…

Metamessage(also: Designer's Metamessage)

In Semiotic Engineering theory, the overarching one-way message that a designer sends to users through the system's interface, communicating who the system is for, what it can do, how to use it, and why it was designed that way. The metamessage is encoded through interface signs…

Microinteraction(also: Micro-interaction, Quick interaction)

A brief, high-frequency interaction with a device that typically takes a sighted user less than four seconds to complete, such as checking the time, glancing at a notification, or adjusting the volume. Microinteractions are significant for accessibility because they expose…

Mixed-Initiative Design(also: Mixed-Initiative Interaction)

An interaction design approach in which both the system and the user can take initiative in directing the flow of interaction, rather than one party being entirely in control. In accessibility contexts, mixed-initiative design is used to balance automated system actions (such as…

Mixed-Initiative Interaction(also: Mixed-Initiative Systems, Human-Agent Collaboration)

An interaction paradigm in which both the human user and the computer system can take initiative in directing the task, rather than one party being entirely in control. In accessibility contexts, mixed-initiative interaction is particularly important for AI-powered assistive…

Mixed-ability group(also: Mixed-ability setting, Inclusive group)

A group composed of individuals with and without disabilities who participate together in shared activities such as research, education, or design. Mixed-ability groups are valued in accessibility practice because they reflect real-world diversity and can foster inclusive design…

Modality(also: Interaction Modality, Interface Modality)

The sensory channel or communication method through which a user interacts with a computer system, such as visual (graphical displays), auditory (speech or non-speech audio), tactile (braille, haptic feedback), or textual (command-line) output, and keyboard, mouse, voice,…

Model Human Processor(also: MHP, Human Processor Model)

A cognitive architecture developed by Card, Moran, and Newell (1983) that models human information processing as three interconnected subsystems: perceptual, cognitive, and motor processors, each with characteristic cycle times. The perceptual processor (~100ms) handles sensory…

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…

Multimodal Features(also: multimodal data, multimodal fusion)

Information extracted from multiple sensory channels or data types—such as combining visual (RGB), depth, audio, and skeletal data—to improve recognition accuracy. In accessibility systems, multimodal approaches often outperform single-modality methods because different data…

Multimodal Natural Language Generation(also: Multimodal NLG)

Natural language generation systems that produce output coordinated across more than one modality — typically combinations of text or speech with graphics, maps, animation, gesture, or tactile output. Multimodal NLG systems decompose their output into several "channels" that are…

NGOMSL(also: Natural GOMS Language)

A structured notation for writing GOMS (Goals, Operators, Methods, Selection rules) models in a program-like form that is readable by humans. NGOMSL was developed by David Kieras as a more formal variant of GOMS that includes selection rules and allows operators at the keystroke…

Natural Language Query(also: NLQ, Conversational Query, Natural Language Search)

An interaction paradigm where users pose questions or issue commands in everyday language rather than using structured search syntax, predefined filters, or navigation controls. In accessibility contexts, natural language querying is particularly valuable for screen reader users…

Natural User Interface(also: NUI)

A user interface designed to feel intuitive and invisible, allowing users to interact with technology through natural behaviors such as gestures, voice, touch, or body movement rather than learned conventions like mouse clicks or keyboard commands. NUIs are particularly valuable…

Networked Minds Social Presence Inventory(also: Networked Minds Measure of Social Presence, NMSPI)

The Networked Minds Social Presence Inventory is a self-report questionnaire developed by Biocca, Harms and colleagues to measure social presence - the sense of 'being together' with another person - in mediated environments such as video calls, virtual reality or augmented…

Non-Speech Input(also: Non-Speech Acoustic Input, Non-Verbal Voice Input)

A method of controlling computers or devices using sounds produced by the human vocal tract that are not recognised words — such as humming, whistling, hissing, clicking, or varying pitch and volume. Unlike speech recognition, which must wait for a complete utterance before…

Nonspeech Audio(also: Non-Speech Sounds, Auditory Cues)

Audio feedback in user interfaces that conveys information through sounds other than synthesized or recorded speech, including earcons (abstract musical motifs), auditory icons (realistic sounds representing actions or objects), and sonification (data mapped to sound…

Nonverbal communication(also: NVC, Body language, Nonverbal cues)

The transmission of information through channels other than spoken or written language, including facial expressions, eye contact, head gestures, hand movements, body posture, spatial proximity, and tone of voice. Nonverbal communication conveys essential social information…

On-Body Interaction(also: Body-centric interaction, Skin input, On-body input)

An interaction paradigm that uses the surface of the user's own body as an input medium, typically through gestures like taps, swipes, or touches on the skin. On-body interaction leverages tactile and proprioceptive feedback from the user's own body, making it potentially…

Paradox of the Active User

The Paradox of the Active User, identified by Carroll and Rosson (1987), refers to the observation that computer users systematically avoid investing time in learning more efficient tools or methods, even when doing so would yield significant long-term productivity gains. Users…

Parameter Mapping Sonification(also: Parameter Mapping, Auditory Parameter Mapping)

A sonification technique that represents changes in data dimensions through corresponding changes in auditory dimensions such as pitch, loudness, timbre, spatial position (panning), tempo, or reverberation. Unlike auditory icons (which use recognizable real-world sounds) or…

Participatory design(also: Co-design, PD, Cooperative design)

A design methodology originating from Scandinavian workplace practices in the 1970s in which end users, stakeholders, and designers collaborate as equal partners throughout the design process. In accessibility, participatory design is essential for ensuring that products and…

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…

Pen-based Interface(also: Stylus Interface, Pen Computing, Digital Pen Interface)

A computer interaction method that uses a stylus or digital pen as the primary input device, typically in combination with a graphics tablet or touchscreen. Pen-based interfaces can support handwriting recognition, gesture commands, and direct manipulation of on-screen objects.…

Perception-Action Cycle(also: PAC)

In human-computer interaction research, the perception-action cycle (PAC) describes the continuous loop in which a user perceives information from the environment — such as the position of an on-screen element — and uses that perception to guide a motor action. The term…

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 Gap

A design failure identified by Choudhury (2026) in which an AI system's explanation is delivered through exactly the sensory channel that its user cannot access. For example, a Grad-CAM heat map overlaid on an image tells a blind user where the model looked but cannot be seen by…

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…

Persuasive Technology(also: Behaviour Change Technology, Behavior Change Technology)

Technology designed to change users' attitudes or behaviours through persuasion and social influence rather than coercion. In health and wellness contexts, persuasive technologies use strategies such as goal-setting, self-monitoring, reminders, social comparison, and rewards to…

Persuasive Technology(also: Captology, Behavior Change Technology)

Interactive computing systems designed to change users' attitudes or behaviors through persuasion rather than coercion. Common persuasive techniques include goal-setting, self-monitoring, rewards, reminders, and social comparison. While persuasive technology has shown success in…

Physical Agency(also: Bodily Agency, Sense of Agency)

The feeling of control and ownership over physical actions and their effects in the world. In assistive technology contexts, physical agency refers to a users sense of directly controlling objects and receiving sensory confirmation of their actions. Traditional AT designs often…

Physical Control(also: Direct Control, Direct Manipulation)

An interaction paradigm where the user directly manipulates on-screen objects or controls by pointing to them and acting on them, as with a mouse click or touch screen tap. In physical control, the focus or cursor moves among all visible interface elements, and the user must…

Pilot-Passenger Model(also: Pilot/Passenger Framework)

A model describing household technology dynamics where "pilots" are the users who set up and configure devices, while "passengers" are those who simply use the systems configured for them. In disability contexts, disabled users may be forced into the passenger role due to…

Pitch Detection(also: Pitch Tracking, Fundamental Frequency Detection)

The computational process of determining the fundamental frequency (pitch) of an audio signal in real time. In accessibility, pitch detection is used in non-speech voice interfaces where changes in humming or vocal pitch are mapped to control commands — for example, a rising…

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…

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 Task(also: Target Acquisition Task, Fitts' Task)

A fundamental human-computer interaction task in which users move a cursor (via mouse, touchpad, finger, or other input device) to click or tap on a target. Pointing tasks are governed by Fitts' Law, which predicts that movement time increases with distance to the target and…

Procedural Task Tracking(also: Task Progress Tracking, Step Tracking)

The automated monitoring of a user's progress through a multi-step task, identifying which steps have been completed, which are in progress, and which remain. In accessibility contexts, procedural task tracking enables assistive systems to provide context-sensitive guidance…

Programming by Demonstration(also: PBD, Record and Replay, Macro Recording)

A technique for creating automated sequences of actions by recording a user performing the task manually, rather than requiring the user to write code or scripts. The system observes the user's interactions (clicks, keystrokes, form inputs) and generates replayable instructions.…