Augmentative & Alternative Communication (AAC) Devices
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Introduction
Augmentative and alternative communication (AAC) includes all forms of communication (other than oral speech) that are used to express thoughts, needs, wants, and ideas. We all use AAC when we make facial expressions or gestures, use symbols or pictures, or write.
People with severe speech or language problems rely on AAC to supplement existing speech or replace speech that is not functional. Special augmentative aids, such as picture and symbol communication boards and electronic devices, are available to help people express themselves. This may increase social interaction, school performance, and feelings of self-worth.
AAC users should not stop using speech if they are able to do so. The AAC aids and devices are used to enhance their communication.
There are 2 types of AAC systems
- Unaided communication systems – rely on the user's body to convey messages. Examples include gestures, body language, and/or sign language.
- Aided communication systems – require the use of tools or equipment in addition to the user's body. Aided communication methods can range from paper and pencil to communication books or boards to devices that produce voice output (speech generating devices or SGD's)and/or written output. Electronic communication aids allow the user to use picture symbols, letters, and/or words and phrases to create messages. Some devices can be programmed to produce different spoken languages.
Unaided Communication Systems
Unaided Communication systems are those that do not require an external tool, and include facial expression, vocalizations, gestures, and sign languages and systems. Informal vocalizations and gestures such as body language and facial expressions are part of natural communication, and such signals may be used by those with profound disabilities. More formalized gestural codes exist that lack a base in a naturally occurring language. For example, the Amer-Ind code is based on Plains Indian Sign Language, and has been used with children with severe-profound disabilities, and adults with a variety of diagnoses including dementia, aphasia and dysarthria. The benefits of gestures and pantomime are that they are always available to the user, usually understood by an educated listener, and are efficient means of communicating.
In contrast, sign languages have a linguistic base and permit the expression of an unlimited number of messages. Approaches to signing can be divided into two major categories:
- those that encode an existing language e.g. American Sign Language
- those that are languages in their own right e.g. Signing Exact English
Signing is used alone or in conjunction with speech to support communication with individuals with a variety of disorders. The specific hand shapes and movements of sign and gesture require an individual to have adequate fine motor and motor planning skills. Sign languages require more fine-motor coordination and are less transparent in meaning than gestural codes such as Amer-Ind; the latter limits the number of people able to understand the person's communication without training.
Aided Communication Systems
Aided communication systems can be divided into 2 types:
- Low-tech communication aids
- High-tech
Low-tech Communication Aids
Low-tech communication aids are defined as those that do not need batteries, electricity or electronics. These are often very simple communication boards or books, from which the user selects letters, words, phrases, pictures, and/or symbols to communicate a message. Depending on physical abilities and limitations, users may indicate the appropriate message with a body part, light pointer, eye-gaze direction, or a head/mouth stick. Alternatively, they may indicate yes or no while a listener scans through possible options.
High-tech Communication Aids
High-tech communication aids permit the storage and retrieval of electronic messages, with most allowing the user to communicate using speech output. Such devices are known as speech generating devices (SGD) or voice output communication aids (VOCA). A device's speech output may be digitized and/or synthesized: digitized systems play recorded words or phrases and are generally more intelligible while synthesized speech uses text-to-speech software that can be harder to understand but that permits the user to spell words and speak novel messages.
High-tech systems may be dedicated devices developed solely for AAC, or non-dedicated devices such as computers that run additional software to allow them to function as AAC devices. They may be static or dynamic in form. Static communication devices have symbols in fixed positions on paper overlays, which are changed manually. To increase the vocabulary available, some static devices have multiple levels, with different words appearing on different levels. On dynamic AAC devices, the user can change the symbols available using page links to navigate to appropriate pages of vocabulary and messages.
High-tech devices vary in the amount of information that they can store, as well as their size, weight and thus their portability. Access methods depend on the abilities of the user, and may include the use of direct selection of symbols on the screen or keyboard with a body part, pointer, adapted mice or joysticks, or indirect selection using switches and scanning. Devices with voice output offer its user the advantage of more communicative power, including the ability to initiate conversation with communication partners who are at a distance. However, they typically require programming, and tend to be unreliable. Because of the latter, low tech systems often recommended as a backup in case of device failure.
Symbols
Symbols used on high and low-tech AAC systems include graphic, auditory, gestural and textural symbols to represent objects, actions and concepts. For users with literacy skills, both low and high-tech devices may use alphabet-based symbols including individual letters, whole words, or parts thereof. With low-tech devices, the communication partner must interpret the symbols chosen whereas a high-tech device can speak the created message aloud. Several large graphic symbol sets have been developed; these include Blissymbols, which possess linguistic characteristics such as grammatical indicators, and the more iconic Picture Communication Symbols (PCS) which do not. Tactile symbols are textured objects, real objects or parts of real objects that are used as a communication symbols particularly for individuals with visual impairments and/or significant intellectual impairments. Auditory symbols such as choices of spoken words or Morse code can also be integrated with assistive technology for the visually impaired.
The choice of symbols and aspects of their presentation, such as size and background, depend on an individual's preferences as well as their linguistic, visual, and cognitive skills.
Access and selection methods
Technological advances have dramatically increased the types of selection methods available for individuals with communication impairments. In "Direct Selection", the selection is made by pointing to the desired symbol using a finger or an alternative pointer, such as eye gaze, a head stick, head- or eye-controlled mouse. To accommodate motor control difficulties some users use alternative activation strategies; for example in "timed activation", the user maintains selection of the symbol for a predetermined period of time until it is recognized by the system. With the "release activation", the selection of the item is only made when the person releases contact from the display.
Direct activation of an AAC system is generally the first choice of access method as it is faster and cognitively easier. Those unable to do so may use indirect selection or "scanning". In this method, items displayed for selection are scanned; the scanning may be visual using indicators such as lights, highlighting, and/or contrasting borders, or auditory using spoken prompts from a communication partner or device. When the desired message is reached, the AAC user indicates the choice using an alternative selection technique such as a switch, vocalization or gesture. Several different patterns for switch access scanning are available: in "circular scanning", the items are displayed in a circle and then scanned one at a time. It is often introduced first to children or beginning AAC users because it is the easiest to understand. In "linear scanning", items are organized in rows and are scanned one at a time until a choice is made. Although more demanding than circular scanning, it is still easy to learn. Finally, in "group-item scanning", items are grouped and the groups scanned consecutively. Once a particular group is selected, items within the group are scanned. One of the most common group-item strategies is row-column scanning in which each row forms a group. The rows of items are scanned and when a row is selected, the items in the row are scanned one at a time until a message is selected.
There are three main selection control techniques in scanning. In "automatic scanning", the scan proceeds at a pre-determined speed and pattern until the user selects an item. In "inverse scanning", the switch is held down to advance the scan, and released to choose the desired item. In "step scanning", the AAC user activates one switch to move the indicator through the items, and another switch to select the item.
Vocabulary organization
Vocabulary organization refers to the way pictures, words, phrases, and sentences are displayed on the communication system. In general, the goal is to facilitate efficient and effective communication, especially when the individual's AAC system contains a large number of symbols.
Communication books and devices are often presented in a grid format; the vocabulary items displayed within them may be organized by spoken word order, frequency of usage or category. In the Fitzgerald Key organization, symbols from different semantic and syntactic classes are organized grammatically in groups from left to right to facilitate sentence construction. Since research has shown that children and adults use a small number of words frequently, in a core-fringe vocabulary organization, the words and messages that are communicated most frequently appear on a "main page". The fringe vocabulary—words and messages used more rarely and that are specific to an individual—appear on other pages. Symbols may also be organized by category, grouping people, places, feelings, foods, drinks, and action words together. Another form of grid organization groups vocabulary according to specific activities. Each display contains symbols for the people, places, objects, feelings, actions, and other relevant vocabulary items for a specific activity or routine.
Visual scene displays are a different method of organizing and presenting symbols. These are depictions of events, people, objects, and related actions in a picture, photograph, or virtual environment representing a situation, place, or specific experience. They are similar to activity displays in that they contain vocabulary that is associated with specific activities or routines. For example, a photo of a child's room may be included in the child's AAC system. Objects and events within the photograph are then used as symbols for communication. Research suggests that visual scene displays are easier than grid displays for young children or those with cognitive impairments to learn and use.
