Glossary

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Progressive Enhancement

A web design strategy that starts with a baseline of essential content and functionality that works in any browser or with any internet connection, then layers on enhanced features for users with more capable browsers or greater bandwidth. Rooted in the "graceful transformation"…

Project Gutenberg

The oldest mass digital-library project, founded by Michael Hart in 1971, offering tens of thousands of public-domain ebooks in plain text, HTML, and EPUB. Project Gutenberg titles are widely used as a free accessible-text source by people with print disabilities, and its…

Project Sidewalk

An open-source web-based crowdsourcing tool developed at the University of Washington that enables volunteers to virtually audit sidewalk accessibility using Google Street View panoramas. Contributors label four types of accessibility features and problems: curb ramps, missing…

Proliferative Diabetic Retinopathy(also: PDR)

An advanced stage of diabetic retinopathy in which abnormal new blood vessels grow on the retina, causing bleeding, scarring, and progressive vision loss that can include blurred vision, floaters, dark spots, and partial or complete blindness. A major cause of acquired low…

Prolific

An online participant recruitment platform used in academic research that allows researchers to screen and recruit participants based on demographic criteria including disability status. Prolific and similar platforms (such as Amazon Mechanical Turk) have been increasingly used…

Prompt Chaining(also: Chained Prompting, Sequential Prompting)

A technique for interacting with large language models where multiple prompts are issued in sequence, with each prompt building on the output of the previous one to achieve a more refined or accurate result. In accessibility and bias mitigation contexts, prompt chaining enables…

Prompt Contradiction

A type of large language model failure in which the system disregards explicit instructions or constraints given in the user prompt, producing output that contradicts what was asked. For example, an AI responding with visual instructions like "click the green button" after the…

Prompt Engineering(also: Prompt Design, Prompt Crafting)

The practice of designing and structuring input prompts to guide large language models (LLMs) toward producing more accurate, relevant, and useful outputs. In accessibility contexts, prompt engineering techniques such as role-play prompting (assigning expert personas),…

Prompt Injection(also: Indirect Prompt Injection, Prompt Engineering Attack)

A technique — originally an LLM security concern — in which carefully crafted instructions embedded in a user prompt or referenced content override the model's intended behaviour, constraints, or safety rules. In accessibility research and practice, the term is increasingly used…

Prompt engineering(also: Prompt design, Prompt crafting)

The practice of designing and iteratively refining natural language inputs to large language models to elicit more accurate, relevant, or useful responses. In accessibility contexts, prompt engineering is an emerging skill that enables disabled users to customise AI interactions…

Prompting System(also: Prompting Device, Task Prompting Technology)

An assistive technology that provides stepwise guidance through text, images, audio, or video instructions to help individuals complete multi-step tasks such as cooking, personal hygiene, or workplace activities. Prompting systems are widely used to support people with cognitive…

Pronominal Reference(also: Pronoun Reference, Anaphoric Reference)

The use of pronouns or pronoun-like expressions to refer back to entities previously introduced in a discourse. In spoken and written languages this is typically achieved with words such as "he," "she," "it," or "they"; in American Sign Language and other signed languages,…

Proportional Font(also: variable-width font)

A typeface in which characters have varying widths based on their natural proportions—a narrow "i" takes less space than a wide "m". Most fonts used in everyday reading are proportional, including Arial, Times New Roman, and Verdana. While proportional fonts create a more…

Proprioception(also: Proprioceptive Sense, Body Position Sense)

The body's ability to sense its own position, movement, and orientation in space without relying on vision. Proprioceptive information comes from sensory receptors in muscles, tendons, and joints that detect stretch, tension, and pressure. For people who are blind or have low…

Prosociality(also: Prosocial Behavior, Prosocial Behaviour)

Prosociality refers to voluntary behaviour intended to benefit others, including helping, sharing, comforting, and cooperating. In accessibility and dementia research, prosocial acts observed during group activities - passing a card so a peer can see it, a reassuring touch on…

Prosodic Breaks(also: Prosodic Pauses, Prosodic Boundaries)

Pauses or breaks in the flow of communication that convey grammatical, syntactic, or emphatic meaning. In sign language, prosodic breaks occur between signs and serve functions similar to intonation and pausing in spoken language — marking sentence boundaries, separating clauses…

Prosody(also: Speech Prosody, Intonation Patterns)

The patterns of stress, rhythm, intonation, and timing in speech that convey meaning beyond the literal words. Prosody communicates emotions, emphasis, questions versus statements, sarcasm, and conversational cues like turn-taking signals. For AAC users relying on text-to-speech…

Prosopagnosia(also: Face Blindness)

A neurological condition characterised by the inability to recognise familiar faces, despite otherwise intact visual and cognitive abilities. People with prosopagnosia may fail to recognise family members, friends, or colleagues by face alone, instead relying on alternative cues…

Prospective Memory

The ability to remember to carry out intended actions in the future, such as taking medication at a specific time, attending an appointment, or completing a task when a particular cue arises. Prospective memory is distinct from retrospective memory (remembering past events) and…

Prosthesis(also: Prosthetic, Prosthetic Device, Artificial Limb)

A prosthesis is an artificial device that replaces a missing body part, which may be lost through congenital conditions, injury, or disease. Prostheses range from purely cosmetic devices designed to replicate natural appearance, to functional devices that restore some degree of…

Prosthesis(also: Prosthetic, Prosthetic device, Artificial limb)

A prosthesis is an artificial device that replaces a missing body part, most commonly a limb. Prosthetics range from cosmetic devices that restore appearance to functional devices that enable specific activities. Modern prosthetics may include mechanical components, myoelectric…

Prosthetics(also: Prostheses, Prosthetic Devices, Artificial Limbs)

Artificial devices designed to replace missing body parts, most commonly limbs lost through amputation, congenital absence, or trauma. Modern prosthetics range from basic cosmetic devices to highly functional myoelectric arms controlled by muscle signals and…

Prosumer(also: Producer-Consumer, Prosumer Content Creator)

A person who both produces and consumes content, particularly on the web. Prosumers are not formally trained in web design or development but are responsible for creating and managing user-generated content shared online — such as blog posts, newsletters, community websites, and…

Protactile Language(also: Pro-Tactile, PT)

A fully touch-based language developed by the DeafBlind community that redefines communication through physical contact, including taps, squeezes, and shared contact space. Protactile Language represents a striking example of a communication micro-culture, where a community…

Protanomaly(also: Protan Anomalous Trichromacy)

A type of colour vision deficiency where the long-wavelength (red) cone cells have a shifted sensitivity range rather than being absent entirely. Protanomaly is a milder form of protan CVD compared to protanopia, resulting in reduced but not absent ability to distinguish reds…

Protanopia(also: Protan Dichromacy, Red-Blind)

A type of colour vision deficiency caused by the complete absence of long-wavelength (red) cone cells in the retina. People with protanopia cannot distinguish between red and green and perceive reds as significantly darker than people with typical colour vision. This darkening…

Protected Characteristic(also: Protected Class, Protected Ground)

A personal attribute that is protected from discrimination under equality legislation. Under the UK Equality Act 2010, the nine protected characteristics are: age, disability, gender reassignment, marriage and civil partnership, pregnancy and maternity, race, religion or belief,…

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…

Prototyping(also: Prototype)

The iterative creation of tangible, interactive representations of a design - ranging from paper sketches and cardboard mock-ups to functional software builds - used to explore ideas, elicit feedback, and test assumptions before committing to a final product. In accessibility…

Provenance Indicator(also: Source Attribution)

Information that identifies which AI model, trial, or prompt produced a particular piece of content in a multi-model comparison. Provenance indicators help users understand which models generate which claims, enabling them to build mental models of individual model strengths and…

Provocation (HCI)(also: Design provocation, Provotype)

In human-computer interaction, a designed artifact whose purpose is to unsettle assumptions, provoke debate, or surface hidden values rather than to solve a defined problem. Provocations draw on traditions of critical design (Dunne and Raby), adversarial design (DiSalvo),…

Proxemic Interaction(also: Proximity-Based Interaction, Proxemics)

An interaction design approach that uses the spatial relationship between users, devices, and objects in the environment — including distance, orientation, and movement — to trigger contextual actions and content delivery. Derived from Edward T. Hall's theory of proxemics (the…

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…

Proximity Detection(also: Proximity Sensing, Proximity-Based Localization)

A method of determining a user's approximate location by measuring their closeness to known reference points, such as BLE beacons or Wi-Fi access points, based on signal strength. In accessible indoor navigation systems, proximity detection is used to localize users at specific…

Proxy(also: Support Person, Intermediary User)

In accessibility contexts, a person who assists someone with a disability in using technology or accessing services. Proxies may include family members, caregivers, support workers, or friends who help with tasks ranging from physical operation of devices to interpretation of…

Proxy Account(also: Delegate Account)

A formal mechanism within a digital system that allows an authorized person to perform tasks on behalf of another user with defined permissions and accountability. In financial technology, proxy accounts enable financial delegates to help older adults or people with disabilities…

Proxy Feedback(also: Proxy User Testing, Surrogate Feedback)

A user research method in which feedback on designs or prototypes is gathered from people who are close to the target users — such as carers, therapists, family members, or support workers — rather than from the users themselves. This approach is used when direct communication…

Proxy Interface(also: Accessibility Proxy, Alternative Interface)

An intermediary user interface that sits between the user and the original content, re-presenting information in a more accessible format without modifying the underlying source. In accessibility contexts, proxy interfaces are used to transform visually-encoded content (like…

Proxy User(also: Proxy Participant, Surrogate User)

A person without a disability who participates in research or usability testing as a stand-in for the intended end user with a disability. Proxies are commonly used in AAC and assistive technology research to circumvent challenges in recruiting and communicating with…

Proxy stakeholder(also: Proxy informant, Proxy respondent)

In requirements engineering and participatory design, a proxy stakeholder is a person—such as a caregiver, support worker, family member, or healthcare professional—who actively mediates, interprets, and scaffolds technology use on behalf of a primary user who faces barriers to…

Pseudo-Attraction Force

A haptic illusion technique that creates the sensation of being pulled or pushed in a specific direction by exploiting the nonlinear relationship between physical and perceived acceleration. The technique uses asymmetric oscillation: a strong, brief acceleration in the intended…

Pseudo-participation(also: Pseudo-participation by Design)

A term coined by Palacin et al. (2020) to describe forms of user involvement in design that appear participatory on the surface but grant participants limited power to shape outcomes. In accessibility and AI contexts, pseudo-participation occurs when disabled people are invited…

Pseudobulbar Affect(also: PBA, Emotional Incontinence, Involuntary Emotional Expression Disorder)

A neurological condition characterized by episodes of involuntary, exaggerated, or inappropriate emotional expression — such as uncontrollable laughing or crying — that may not match the person's actual emotional state. Pseudobulbar affect occurs after damage to the neural…

Pseudonymization(also: Pseudonymisation, De-identification)

A privacy technique in which personally identifying fields are replaced with artificial identifiers — typically hashes, tokens, or randomly assigned IDs — so that the data can no longer be attributed to a specific person without additional information kept separately. Recognised…

Psychoacoustics

The branch of perceptual psychology that studies how humans subjectively perceive sound - loudness, pitch, timbre, spatial location, foreground/background segregation, and masking. Psychoacoustic principles underpin accessible audio design: screen reader pacing, earcon and…

Psychoeducation

The process of providing education about a mental health condition, its symptoms, treatment options, and management strategies to individuals with the condition and their support networks. For OCD, psychoeducation helps people understand the nature of obsessions and compulsions,…

Psycholinguistics

The scientific study of the cognitive and neural processes that underlie the production, comprehension, and acquisition of language. Psycholinguistic research measures phenomena such as reading and signing rate, comprehension under time pressure, lexical access, and the role of…

Psychological Accessibility

A dimension of accessibility concerned with whether users find a product or service useful, appropriate, and satisfying, beyond being merely technically operable. Psychological accessibility addresses factors such as user confidence, willingness to engage with technology, and…

Psychometric Evaluation(also: Psychometric Validation, Psychometric Analysis)

The process of assessing whether a measurement instrument (such as a questionnaire or survey) possesses desirable statistical properties including validity, reliability, and consistency. In accessibility and usability research, psychometric evaluation is used to determine…

Psychometric Test(also: Psychometric Assessment, Psychometric Evaluation)

A standardised measurement instrument designed to assess an individual's cognitive abilities, motor skills, perceptual speed, or other psychological attributes. In accessibility research and usability evaluation, psychometric tests such as the Mini-Mental State Examination…