Glossary

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AAC Corpus(also: AAC Text Corpus, Augmentative Communication Corpus)

A collection of text produced by or representative of Augmentative and Alternative Communication (AAC) device users, used for training and evaluating language models and word prediction systems. AAC corpora are notoriously difficult to assemble because AAC users produce text…

AAC Symbol Set(also: Symbol Set, Communication Symbol Set, Pictographic Symbol Set)

A standardised collection of pictographic images used in augmentative and alternative communication (AAC) to represent words, phrases, or concepts. Each symbol in a set is mapped to specific vocabulary, allowing people who cannot use spoken language to construct messages by…

Aided AAC(also: Aided Augmentative and Alternative Communication)

The branch of Augmentative and Alternative Communication that relies on an external tool to produce or carry the message — ranging from low-tech paper communication boards and picture-exchange cards to high-tech tablet apps and dedicated speech-generating devices accessed via…

Augmentative and Alternative Communication(also: AAC)

A set of tools, strategies, and techniques used to supplement or replace spoken or written communication for people with complex communication needs. AAC ranges from low-tech options like picture boards and symbol cards to high-tech solutions including speech-generating devices…

Augmentative and Alternative Communication(also: AAC)

A range of methods, devices, and strategies used to supplement or replace speech for individuals who have difficulty producing or comprehending spoken language. AAC encompasses both unaided approaches (such as gestures, sign language, and facial expressions) and aided approaches…

BIGmack Switch(also: BIGmack, BIGmack Communicator)

A single-message assistive technology device that allows a user to press a large button to play a pre-recorded message. BIGmack Switches are widely used in special education and communication interventions for individuals with significant speech and motor disabilities, including…

Blissymbols(also: Blissymbolics, Bliss Language)

A symbolic language created by Charles K. Bliss, consisting of several hundred basic symbols that can be combined to create new meanings. Unlike pictographic symbol sets where each image represents a specific word, Blissymbols are ideographic — they represent concepts rather…

Buddy Button

A widely used commercial assistive technology switch manufactured by AbleNet, designed for single-switch access to computers, communication devices, and adapted toys. Buddy Buttons are large, colorful, easy-to-activate mechanical switches that can be positioned on various body…

Choice-Making(also: Choice Board, Aided Choice)

A structured communication and learning strategy in which an individual is presented with two or more options and supported to make a selection, often using pictures, objects, or symbols. Choice-making is a foundational skill in autism education and therapy, serving multiple…

Clutching(also: Clutch Mechanism, Clutch Gesture)

In gesture- and motion-based input systems, a mechanism that lets the user temporarily disengage the recogniser so that everyday, non-communicative movements — reaching, adjusting posture, gesturing socially — do not trigger false activations. Named after the mechanical clutch…

Communication Asymmetry(also: Interaction Asymmetry, Communication Imbalance)

The imbalance in communication capabilities, speed, or modalities between conversation partners. In AAC contexts, communication asymmetry arises because AAC users communicate at 12-18 words per minute compared to 125-185 for typical speakers, creating fundamental differences in…

Communication Breakdown(also: Conversational Breakdown, Communication Failure)

A disruption in conversation where the intended message is not successfully conveyed or understood, leading to confusion, misunderstanding, or loss of conversational coherence. In AAC communication, breakdowns can occur when backchanneling cues are missed (because the partner is…

Communication Partner(also: CP, Conversation Partner)

A person who communicates with an AAC user, whether through speech, sign, or other means. Communication partners play a critical role in the success of AAC interactions — their willingness to wait, their ability to interpret messages, and their understanding of AAC devices…

Computerized Visual Communication(also: C-VIC)

A computer-based assistive technology system that enables people with aphasia to communicate by arranging icons and images on screen to form sentences, which can then be translated into spoken or written language. C-VIC systems use structured visual vocabularies where users…

Conversational Management(also: Conversation Management, Interactional Management)

The processes by which interlocutors jointly regulate the structure of a conversation - taking and ceding turns, pre-empting interruptions, shifting attention and topic, repairing misunderstandings, and maintaining flow over time. In AAC research, conversational management is a…

DECTalk

A text-to-speech synthesis system originally developed by Digital Equipment Corporation in the 1980s, using rule-based formant synthesis to generate speech from text input. DECTalk offered several preset voices (including "Paul" and "Betty") and was widely adopted in AAC…

Delegated Agency(also: Delegated Technical Agency)

Delegated agency occurs in augmentative and alternative communication (AAC) when a close conversation partner (such as a parent or aide) acts on behalf of an augmented communicator to advance the communicator's conversational goals. This may include expanding on the…

Digital Storytelling(also: Multimedia Storytelling, Personal Digital Narrative)

The use of digital media — including photographs, video clips, audio recordings, and text — to create and share personal narratives. In the context of accessibility and AAC, digital storytelling offers an alternative to text-based and real-time spoken communication, allowing…

E-Tran Frame(also: Eye-Transfer Frame, Eye-Pointing Frame, ETRAN)

A low-technology augmentative and alternative communication (AAC) device consisting of a transparent frame or board that allows a person to communicate by directing their eye gaze toward symbols, letters, words, or colour-coded groups arranged on the frame. The communication…

Ethnomethodology

A sociological approach, founded by Harold Garfinkel, that studies the everyday methods people use to make sense of and produce social order in interaction - the implicit rules and shared practices through which we treat ordinary situations as ordinary. Conversation analysis…

Expressive Communication(also: Expressive AAC, Rich Communication)

Communication that conveys not just informational content but also emotion, personality, attitude, humor, and social nuance. For AAC users, achieving expressive communication is a significant challenge because most AAC technology prioritizes efficient message transmission over…

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

The use of eye movements and gaze direction as a means of communication, either naturally (making eye contact, looking at objects to indicate interest) or through technology (eye-tracking systems that allow users to select items on a screen by looking at them). For AAC users,…

Huffman Coding(also: Huffman Algorithm, Huffman Tree)

A data compression algorithm that assigns shorter codes to more frequently occurring symbols and longer codes to less frequent ones, producing an optimal prefix-free encoding. In accessibility and AAC research, Huffman coding has been applied to the design of scanning interfaces…

Idiosyncratic Gesture(also: Personalised Gesture, Idiosyncratic Movement)

A body-based communicative movement whose form and meaning are specific to one individual (and often to one communication partner), rather than drawn from a shared vocabulary like American Sign Language. Idiosyncratic gestures are central to unaided AAC for many people with…

Indirect Text Entry(also: Indirect Selection, Indirect Text Composition)

A text input method where the number of available input controls (such as switches or keys) is significantly smaller than the number of characters that can be entered. The user selects characters through an intermediary process such as scanning, where the system cycles through…

Input Rate(also: Keystroke Rate)

The speed at which a user can produce individual keystrokes or character inputs, typically measured in seconds per keystroke. Input rate varies dramatically across access methods: touch typists may achieve 0.1-0.2 seconds per keystroke, while users of switch scanning systems or…

Interaction Symmetry(also: Balanced Interaction)

The degree to which conversation partners have equal opportunities and means to participate in an interaction. In face-to-face spoken conversation, interaction is relatively symmetric—both partners can speak, listen, and use non-verbal cues at comparable speeds. AAC…

Keystroke Saving(also: KS, Keystroke Reduction)

A metric used to evaluate word prediction and word completion systems, measuring the percentage of keystrokes that a user can avoid by accepting system predictions instead of typing each character individually. Keystroke saving is calculated by comparing the number of keystrokes…

Keystroke Savings(also: KS, Key Savings)

A metric used to evaluate word prediction systems, measuring the percentage of keystrokes eliminated by accepting predictions compared to typing the full text character by character. While keystroke savings is commonly reported in AAC research, it does not directly translate to…

Lingraphica

A commercially available computerized visual communication system designed to help people with aphasia communicate through icon-based sentence construction. Lingraphica provides a vocabulary of purpose-designed icons that users can arrange to form phrases and sentences, with the…

Lombard Effect(also: Lombard Reflex, Lombard Response)

The involuntary tendency of speakers to increase the intensity, duration, and fundamental frequency of their speech when communicating in noisy environments. Named after French otolaryngologist Étienne Lombard who first described the phenomenon in 1911, the effect involves…

Memory Aid(also: Memory Wallet, Memory Book, External Memory Aid)

A tool or device that supports memory function by providing external cues, reminders, or stored information that a person can reference. For people with dementia or other cognitive impairments, memory aids may include wallets with photos and captions, communication boards,…

Multi-Modal Communication(also: Multimodal Communication)

Communication that simultaneously uses multiple channels or modes—such as speech, gesture, facial expression, gaze, device output, and body movement—to convey meaning. AAC users are inherently multi-modal communicators, blending whatever channels are available to them to create…

Partner Training(also: Communication Partner Training, Interlocutor Training)

Education and coaching provided to the communication partners of AAC users to help them interact more effectively and supportively. Partner training covers strategies like allowing adequate time for responses, recognizing non-verbal and device-mediated communication cues,…

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…

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…

Pictograms(also: Pictogram, Picture Symbols, PCS)

Simplified pictorial symbols that represent concepts, objects, activities, emotions, or places, widely used as a form of augmentative and alternative communication (AAC) and as a visual support for autistic individuals, minimally verbal users, and people with cognitive…

Picture Communication Symbols(also: PCS, Boardmaker Symbols)

A widely used graphic symbol system for augmentative and alternative communication (AAC), consisting of simple, colorful line drawings representing words, phrases, and concepts. Developed by Mayer-Johnson (now part of Tobii Dynavox), PCS is one of the most common symbol sets…

Picture Exchange Communication System(also: PECS)

A structured augmentative and alternative communication (AAC) system that teaches individuals to use pictures to communicate with others. Developed by Andrew Bondy and Lori Frost in 1985, PECS uses a series of six phases to teach individuals — typically children with autism or…

Pre-Programmed Message(also: Stored Message, Canned Response, Pre-Set Phrase)

A message or phrase stored in an AAC device that can be quickly retrieved and spoken without requiring real-time composition. Pre-programmed messages trade expressiveness for speed—they enable faster communication but are limited to anticipated phrases. For backchanneling,…

Prediction Utilization(also: PU)

The percentage of opportunities where a user accepts a word prediction rather than continuing to type the word manually. Prediction utilization reflects user trust in a prediction system—higher quality predictions lead to higher utilization rates. Research shows that users…

QuickFire(also: Quick Phrases, Quick Response Buttons)

Pre-programmed short phrases or responses stored on AAC devices that can be accessed and played quickly with minimal navigation, typically arranged on a single page for rapid access. QuickFire phrases commonly include backchanneling responses ("yes," "no," "wait"), social…

Remnant book(also: remnant scrapbook, memory book)

An AAC strategy that uses collected physical artifacts—such as ticket stubs, photos, business cards, and other tangible items—organized in a book or album to support communication for people with aphasia or other cognitive-communication disorders. Remnant books leverage…

Response Time(also: Reaction Time, Tact)

The time elapsed between the presentation of a stimulus and the user's physical response, typically measured in milliseconds. In scanning-based AAC, response time (often called Tact) is the interval between when an item is highlighted and when the user activates the switch.…

Row-Column Scanning(also: RCS, Grid Scanning, Two-Switch Scanning)

The most widely used single-switch selection method for augmentative and alternative communication (AAC) devices and on-screen keyboards. Options are arranged in a two-dimensional grid, and the interface sequentially highlights each row. When the user clicks their switch, the…

Scanning(also: Switch Scanning, Automatic Scanning)

An indirect selection method used in augmentative and alternative communication (AAC) and assistive technology where items (letters, words, or commands) are highlighted sequentially by the system, and the user activates a switch to select the currently highlighted item. In…

Scanning Delay(also: Tscan, Scan Rate, Dwell Time)

The time interval a scanning system waits before automatically advancing to highlight the next item. Setting scanning delay appropriately is critical for switch access users: too short causes selection errors because the user cannot respond quickly enough; too long dramatically…

Scanning System(also: Automatic Scanning, Group Scanning, Row-Column Scanning)

An assistive technology input method in which selectable items are sequentially highlighted on screen, and the user activates a switch (or other simple input) when the desired item is highlighted. Scanning systems are designed for people with severe motor disabilities who can…

Semantic Redundancy(also: Redundant Multimodal Input)

A design strategy in multimodal interfaces where the same command or message is conveyed simultaneously through multiple input channels, each independently signalling the user's intent. For example, a user might perform a head nod and a hand gesture at the same time, both…

Single Switch(also: Single Switch Access, One Switch)

An assistive technology input device that provides a single binary action — on or off — enabling people with severe motor impairments to interact with computers and communication devices. Switches can be activated by virtually any reliable voluntary movement, including a blink,…