Glossary

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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.…

Programming by Example(also: PBE, Programming by Demonstration)

A technique in end-user programming where a system infers a generalizable program from concrete examples provided by the user, rather than requiring the user to write code directly. In accessibility contexts, programming by example has been used to enable nonprogrammers to…

Proteus Effect

The Proteus Effect is a phenomenon, first described by Yee and Bailenson (2007), in which the appearance of a person's avatar influences how they think, behave and interact in virtual or augmented environments. For example, users assigned taller or more attractive avatars tend…

Proxemics(also: Interpersonal distance, Personal space)

The study of how people use and perceive physical space in social interactions, originally defined by anthropologist Edward T. Hall in 1966. Hall identified four distance zones: intimate (0–45 cm), personal (45 cm–1.2 m), social (1.2–3.6 m), and public (beyond 3.6 m). In…

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