Augmentative Communication: A Glossary
The following section provides a brief description of some of the terms that are used in augmentative communication. Understanding some of these terms may be helpful as you become involved in your search for an appropriate communication system.
Communication is based on the use of the individual words of our language. True communication is spontaneous and novel. Therefore, communication systems cannot be based significantly on pre-stored sentences. Communication requires access to a vocabulary of individual words suitable to our needs that are multiple and subject to change. These words must be selected to form the sentences that we wish to say.
How we select these words is a function of our abilities and the systems we have available to us. When we cannot speak naturally, other methods of selecting words can be used. These methods have two parts: the language representation method and the physical selection technique.
In some cases, such as with sign language, the communication may be direct to the partner. An electronic AAC system may include speech output which then transmits the words to the communication partner.
Gestures – Some gestures, such as shaking or nodding the head or shrugging the shoulders, are so common that they are generally understood by everyone. Other less obvious, but still easily recognizable, gestures can also be used for communication. For example, the American Indians made up a group of hand signals that they could use for basic communication at their intertribal meetings. These gesture systems are easy to use, but detailed conversation is not possible.
Sign languages – These are languages composed of different hand shapes originally developed for people withsevere hearing loss or deafness. They require a certain amount of manual dexterity, and are not understood well by people who do not know the system. Different sign languages have developed in different countries.
Fingerspelling – Letters are formed by different shapes of the hand and fingers. Each word is then spelled out. Fingerspelling often is used with sign language for spelling of proper names, technical terms, and the like.
Speech – Oral symbols/speech can be spoken by a person or generated by computer.
Language representation methods – Speech output AAC systems use one or a combination of three basic language representation methods: single meaning pictures, alphabet-based methods, and semantic compaction. An understanding of the performance differences and appropriate choices of method(s) are very important to the effectiveness of the communication system.
Single meaning pictures – Each word in the vocabulary is represented by a different picture. Thousands of pictures are needed for a modest vocabulary size. Meanings must be taught since most words are not naturally represented by pictures.
Alphabet-based methods – These include spelling, word prediction, letter codes, and whole words. Literacy is required.
Semantic compaction – This method uses sequences of multi-meaning icons to represent vocabulary items.
Core Vocabulary – The small number of words that are used for the majority of communication. For most people, about 85% of communication is accomplished using just a few hundred words.
Extended vocabulary – The words that are used for the 15% of communication not covered by core vocabulary.
Language activity monitoring – This is the automatic recording of the content and time of language events. The information is then analyzed to produce a report of various quantitative summary measures of communication performance.
There are a variety of different ways to send messages. With good motor control, an individual can produce communication symbols by using speech, gestures, sign language, fingerspelling, writing, head shaking, eye blinks, and other facial and body movements. When an electronic AAC device is used, the device transmits the communication in response to input from the user.
Without adequate motor control, an individual must be taught how to indicate those symbols he or she wants to use. Selection techniques include direct selection, scanning, and encoding. The selection rate has direct impact on the rate of communication. Selection rate can be measured and the fastest technique should be used.
Direct selection – The individual directly indicates the desired symbol, usually by pointing with a body part, such as the finger, thumb, fist, elbow, eyes, foot or knee. Often, a pointing aid is needed. It can be a pointer held in a closed fist, a stick held in the mouth, or a lightbeam mounted in a headband.
If motor control is not good enough for pointing, a number of electronic devices are available to help with selection. One such device uses a very good camera and a high-speed microprocessor to find even very small eye movements. For people who can speak but not write, desired words can be spoken, decoded by computer, and then printed out.
Direct selection generally is faster than other approaches.
Scanning – In scanning, symbol choices are presented to the user one at a time. The user chooses the symbol, or group of symbols, wanted by signaling at the appropriate time.
Scanning can be done with or without electronic equipment. In one of the simplest forms, the user has a chart of pictures representing various personal needs and interests. The communication partner points to each picture one at a time and asks a yes/no question (e.g., "Is this what you want?"). The user answers the question with a head nod or eye blink, and the process is repeated until the correct choice is found.
By using an electronic device, an individual can produce messages independently. A special switch is used to stop a moving light when it comes to the desired symbol. Many different kinds of switches are available that can be used by people who have very limited motor control. Basic scanning is slow, and is useful only when no more than 15 choices are available.
When more choices are needed, other types of scanning have to be used. Choices may be arranged in rows and columns. The user locates the desired symbol, and allows the light to move from column to column until it reaches the right one and then from row to row until the desired symbol is lit.
For even more choices, the user may have a number of different charts with different rows and columns. Through self-selection or answering yes-no questions, the user chooses the chart with the desired symbol on it, and the communication then proceeds just as it did for row and column scanning.
Encoding – With encoding, the user learns to use specific codes for each message. Numerical codes (1 = Can I talk with you a minute?, 2 = I'd like to have pizza for lunch, 3 = Let's pick a movie to see) are the most common, but sequences of letters and shapes also have been used. Encoding can be a very rapid way of expressing lengthy messages.
If mental abilities are better than motor abilities, encoding can provide a greater range of vocabulary options. For example, a vocabulary display may only have room for 10 choices. However, by combining numbers, many more messages can be expressed. For example, I + 3 = "Please leave me alone!"
Usually, both users and communication partners must know the code or have a chart of the codes available. However, some communication devices work by pressing a number code that generates computer speech.