Glossary

Search results

Peripheral Vision(also: Side Vision)

Vision that occurs outside the center of gaze, encompassing the ability to see objects and movement to the sides, above, and below the point of fixation. Peripheral vision is important for spatial awareness, navigation, and detecting motion. Musicians with low vision may rely on…

Perkins Brailler(also: Brailler, Braille Writer)

A mechanical device for writing braille, manufactured by the Perkins School for the Blind since 1951. The Perkins Brailler has six keys corresponding to the six dots of a braille cell, a space bar, a backspace key, and a line advance key, allowing users to emboss braille…

Perpetual Contact

Perpetual contact is a sociological term coined by James Katz and Mark Aakhus to describe the state, enabled by mobile phones and later by ubiquitous internet messaging, in which people maintain constant availability to their social network regardless of physical location. For…

Perplexity(also: Language Model Perplexity)

A standard metric for evaluating language models that measures how well the model predicts a sample of text. Mathematically, perplexity is the inverse probability of the test set, normalised by the number of words — a lower perplexity indicates that the model assigns higher…

Perseveration(also: Perseverative Behavior)

The uncontrolled repetition of a response, word, phrase, or action that persists beyond the appropriate context. In people with cognitive impairments such as dementia, brain injury, or certain developmental disabilities, perseveration can manifest as repeatedly pressing the same…

Person-Centred Care(also: Person-Centered Care, Person-Centred Approach)

An approach to care and support that places the individual — their preferences, needs, values, history, and identity — at the centre of all decisions and interactions, rather than focusing primarily on their diagnosis or deficits. Originated in dementia care through the work of…

Person-Centred Planning(also: Person-Centered Planning, PCP)

A combination of approaches designed to empower people with disabilities to make their own choices and decisions about the support they receive. In accessibility contexts, person-centred planning shifts control from service providers to the individual, recognizing that people…

Person-First Language(also: People-First Language, PFL)

Person-first language is a linguistic convention that places the person before the disability or condition, such as "person with a disability" or "person with autism," with the intent of emphasizing personhood over diagnosis. While widely adopted in professional and medical…

Person-Technology Match(also: PTM, Matching Person and Technology)

A systematic approach to selecting assistive technology by evaluating the fit between a person's specific abilities, needs, preferences, and environment and the features and demands of available technologies. The person-technology match process recognizes that the most…

Persona(also: User Persona, Design Persona)

A fictional but research-based representation of a user group that captures key characteristics, goals, motivations, and needs. In accessibility work, personas are used to represent the diverse experiences and requirements of disabled users, helping design teams maintain empathy…

Persona(also: User Persona, Design Persona)

A fictional character created to represent a type of user who might interact with a product, service, or website. Personas are grounded in research data and typically include details such as name, age, occupation, abilities, goals, frustrations, and technology usage patterns. In…

Persona Design(also: Design Personas, User Personas)

A user-centered design technique in which designers create fictional but grounded profiles of representative users — demographics, goals, context, pain points — to guide design decisions when direct user involvement is limited. In accessibility and HCI co-design workshops,…

Personal Assistant(also: Virtual Assistant, Digital Assistant, Voice Assistant)

A software agent that can perform tasks or provide services based on user commands or queries, typically through voice interaction. Popular examples include Amazon Alexa, Google Assistant, Apple Siri, and Microsoft Cortana, often embedded in smart speakers, smartphones, and…

Personal Care Assistant(also: PCA, Personal Care Attendant, Personal Support Worker)

A person who provides hands-on assistance with activities of daily living (ADLs) to people with disabilities or older adults who need support with tasks such as bathing, dressing, toileting, grooming, eating, and transferring. PCAs may be formally employed through agencies or…

Personal Data Externalization(also: Data Externalization)

The process of representing internal experiences — thoughts, emotions, behaviours, bodily states — in some external medium such as a drawing, written word list, spreadsheet, physical artefact, or tracking log. Drawing on Larkin and Simon's distinction between internal and…

Personal Delivery Device(also: PDD, Delivery Robot, Autonomous Delivery Robot)

Personal delivery devices (PDDs) are small autonomous or semi-autonomous robots that travel on sidewalks and pedestrian pathways to deliver food, packages, and other goods. These devices have been granted pedestrian status under traffic code in several US states, giving them the…

Personal Digital Assistant(also: PDA, Handheld Computer, Pocket PC)

A portable handheld computing device popular in the late 1990s and early 2000s that combined features like a calendar, contacts, note-taking, and basic application support in a pocket-sized form factor with a touchscreen interface. In accessibility research, PDAs like the iPAQ…

Personal Independence Payment(also: PIP)

A UK non-means-tested, points-based disability benefit for working-age adults that helps with the extra costs of long-term physical or mental health conditions. PIP has two components — Daily Living and Mobility — and is awarded based on functional assessments conducted via…

Personal Moderation(also: Self-Moderation, User-Controlled Moderation)

Personal moderation refers to content moderation tools that allow individual users to control what content appears on their own feeds and experiences, as distinct from platform-level decisions that affect all users. Personal moderation actions include muting or blocking…

Personal Narrative(also: Storytelling, Conversational Narrative)

The act of telling others about one's own experiences, events, and feelings — a fundamental aspect of human social interaction. Personal narrative serves multiple functions: building and maintaining relationships, developing identity and sense of self, processing experiences…

Personal Needs and Preferences(also: PNP, Learner Preferences Profile, Access Needs Profile)

Personal Needs and Preferences (PNP) is a component of the AccessForAll framework (standardized in ISO 24751 and IMS AccessForAll) that provides a structured way to describe an individual learner's accessibility requirements and interaction preferences. A PNP profile specifies…

Personal Object Recognizer(also: Teachable Object Recognizer, Custom Object Classifier)

A computer vision system that allows individual users to train their own object recognition models by providing a small number of example photos and custom labels. Unlike generic object recognizers that use pre-defined categories, personal object recognizers let users define…

Personal Safety Management(also: PSM)

Personal Safety Management refers to the informed, agential, and proactive participation of an individual in maintaining their own physical safety. Coined in accessibility research by Branham et al. (2017), the concept highlights how people with disabilities — particularly those…

Personal Space(also: Interpersonal Distance, Personal Distance Zone)

The invisible boundary surrounding a person that they consider their own territory, the violation of which can cause discomfort or stress. Research by Edward T. Hall defined four distance zones: intimate (0-18 inches), personal (18 inches to 4 feet), social (4-12 feet), and…

Personal Voice(also: Voice Banking, AI Voice Clone)

A technology that creates a synthetic replica of a person's voice from recorded speech samples, enabling text-to-speech output that sounds like the individual rather than a generic electronic voice. Apple's Personal Voice feature (iOS 17+) allows users to train an AI model of…

Personal emergency response system(also: PERS, PER system, Medical alert system)

A device, typically a wearable pendant or wristband with a button, that allows a person to summon help in an emergency. Despite being the mainstream solution for older adults living alone, PERS devices suffer from poor adoption: users forget to wear them, find them stigmatizing,…

Personal-Scale Manufacturing(also: Desktop Manufacturing, Personal Fabrication)

The use of affordable, accessible manufacturing tools such as 3D printers, laser cutters, and CNC machines by individuals or small groups to produce custom physical objects, as opposed to relying on industrial-scale production. In the context of assistive technology,…

Personality Test(also: Personality Inventory, Personality Assessment)

A psychometric instrument that attempts to quantify traits such as conscientiousness, extraversion, emotional stability, or risk tolerance. Personality tests were introduced in industry during and after World War I to screen for "maladjusted" workers, and are now the most…

Personalization(also: User Personalization, Interface Personalization)

The adaptation of digital content, interfaces, or experiences to individual user preferences, needs, and contexts. In accessibility, personalization is essential because people with the same type of disability may have very different needs and preferences — for example, some…

Personalization Semantics(also: WAI-Adapt)

A W3C specification that defines standardized semantics enabling content to be adapted to individual user needs and preferences. Personalization Semantics allows web authors to add metadata attributes to HTML elements that describe their purpose, importance, or function in a way…

Personalized Accessibility(also: Personalized Web Accessibility, User-Tailored Accessibility)

An approach to accessibility evaluation and design that considers the specific disability profile, capabilities, and needs of individual users rather than treating accessibility as a single universal property. Personalized accessibility evaluation tools filter WCAG success…

Personalized Dynamic Accessibility(also: Dynamic Accessibility, Adaptive Accessibility)

An approach to accessibility where systems automatically detect user abilities and adapt interface settings in real-time to match current needs. Unlike static accessibility settings that remain constant, personalized dynamic accessibility recognizes that an individual's…

Personalized Learning(also: Adaptive Learning, Individualized Instruction, Differentiated Instruction)

Personalized learning is an educational approach that tailors content, pace, and delivery method to each learner's individual needs, preferences, and abilities. In accessibility contexts, personalization goes beyond selecting appropriate difficulty levels — it requires creating…

Personalized Object Recognition(also: Teachable Object Recognition)

A class of computer vision systems that allow an individual user — typically someone who is blind or has low vision — to train their device to recognize a small set of personally relevant objects (a specific coffee mug, a particular set of keys, a favourite notebook) by…

Personalized accessibility(also: Customizable accessibility, Adaptive accessibility)

An approach to accessibility that allows users to configure assistive features according to their individual needs, preferences, and abilities rather than providing a single fixed accommodation. Personalized accessibility recognizes that disabilities — particularly conditions…

Personally Identifiable Information(also: PII)

Any data that can be used to identify a specific individual, such as name, email address, location, biometric data, or device identifiers. For assistive technology users, PII concerns are heightened because the data collected often reveals sensitive information about a person's…

Personally Identifying Information(also: PII, Personal Data, Personally Identifiable Information)

Any data that can be used to identify a specific individual, including names, addresses, photographs, financial details, and biometric data. In accessibility contexts, PII is a significant concern when disabled users contribute data for AI training, as they may inadvertently…

Personhood

The recognition of a human being as a full person with agency, dignity, self-expression, and moral standing, irrespective of cognitive, physical, or communicative impairments. In dementia care and accessibility practice, affirming personhood means interacting with the individual…

Perspective-taking(also: Cognitive empathy, Theory of mind)

The cognitive ability to understand and consider another person's thoughts, feelings, beliefs, and point of view. In accessibility and neurodiversity contexts, perspective-taking is central to the double empathy problem — research shows that neurotypical individuals struggle…

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…

Perturbation testing(also: Counterfactual testing, Template-based testing)

A bias evaluation methodology for NLP models that systematically substitutes identity-related terms (e.g., disability phrases) in otherwise identical sentences to measure whether the model produces different predictions based on the identity mention alone. By holding all other…

Pervasive Accessible Technology(also: PAT)

A strategy for integrating accessibility directly into information technology infrastructure rather than retrofitting it after the fact. Proposed by Michael Paciello in 1996, Pervasive Accessible Technology combines a Standard Human Interface with an Accessible Information…

Pervasive Developmental Disorder(also: PDD, PDD-NOS, Pervasive Developmental Disorder Not Otherwise Specified)

A historical diagnostic category encompassing a group of neurodevelopmental conditions characterised by delays in socialisation, communication, and restricted patterns of behaviour. Under the DSM-IV, Pervasive Developmental Disorders included autism, Asperger syndrome, childhood…

Pet Robot(also: Robotic Pet, Zoomorphic Robot, Companion Pet Robot)

A socially interactive robot designed to resemble and behave like an animal companion — most famously PARO (a baby harp seal) and AIBO (a robotic dog) — used to provide emotional comfort, reduce loneliness, stimulate engagement, and support therapy for older adults, particularly…

Phantom Limb Pain(also: PLP)

Phantom limb pain is a chronic pain condition in which an individual experiences painful sensations appearing to come from a limb (or other body part) that has been amputated or is no longer functional. The pain is real and neurological in origin, arising from reorganisation of…

Phantom Sensation(also: Phantom Vibration, Vibrotactile Illusion)

A phantom sensation is a perceptual illusion in which two vibrotactile actuators stimulating the skin simultaneously create the feeling of a single vibration at a point between them. By varying the amplitude and frequency of each actuator, the perceived location of the phantom…

Phase-Based Motion Processing(also: Phase-Based Video Motion Processing, Phase-Based Motion Magnification)

A family of computer vision techniques that decompose video frames into complex steerable pyramids and analyse changes in the temporal phase of each scale and orientation to recover motion, including sub-pixel movements invisible to the naked eye. Because it operates in the…

Phenomenology(also: Phenomenological Inquiry)

Phenomenology is a philosophical tradition and research methodology concerned with the structures of lived, first-person experience. Originating with Husserl, Heidegger, and Merleau-Ponty, it emphasizes how phenomena appear to consciousness rather than what they are in objective…

Phoneme(also: Speech Sound)

The smallest unit of sound in a language that can distinguish one word from another. For example, the /b/ and /p/ sounds in "bat" and "pat" are different phonemes. American English has approximately 39 phonemes, compared to 26 letters in the alphabet. In accessibility and AAC…