tems in a selection set that are not intended to be selected, for example, blank items, objects that are disliked, or items that are not appropriate in a given context. These are used to determine reliability or consistency with the communication technique.

A communication system that is based on movements, like gestures, but the meaning is not obvious from the movement and must be learned. AmerInd, which is based on American Indian sign language, is one such system.

Symbols that are abstract representations

A vocabulary specific or unique to a AAC user or to one activity or topic (Beukelman &Mirenda, 1998)

An unaided method of communication that includes facial expressions, eye gazing, hand movements and body postures (Beukelman & Mirenda, 1998) The meaning does not typically have to be learned, but is clear from the movement itself.

The ability to communicate with both familiar and unfamiliar partners about any topic in any context (Dowden 1999). "Independent communication" does not mean that the individual does not rely on technology or assistance from people in the environment.

Usually small words such as of, by, with, etc.

A stick held closely to the head (typically mounted on a cap) and used by individuals with poor hand control to perform some tasks otherwise done by hand, such as reaching and pointing. Some AAC users use headwands to select items on a communication display or device.

Vocabulary that allows the user to create novel messages (Dowden & Cook, 2002)

visual symbols are combined to store words, phrases or sentences. The icons are usually abstract so that there can be multiple meanings associated with them. Encoding is a speed-enhancement technique.