Augmentative and alternative communication

Augmentative and alternative communication (AAC) encompasses the communication methods used to supplement or replace speech or writing for those with impairments in the production or comprehension of spoken or written language. AAC is used by those with a wide range of speech and language impairments, including developmental disabilities such as cerebral palsy, intellectual disability and autism, and acquired conditions such as amyotrophic lateral sclerosis and Parkinson's disease. AAC can be a permanent addition to a person's communication or a temporary aid. Stephen Hawking, probably the best-known user of AAC, had amyotrophic lateral sclerosis, and communicated through a speech-generating device.

Modern use of AAC began in the 1950s with systems for those who had lost the ability to speak following surgical procedures. During the 1960s and 1970s, spurred by an increasing commitment in the West towards the inclusion of disabled individuals in mainstream society and emphasis on them developing the skills required for independence, the use of manual sign language and then graphic symbol communication grew greatly. It was not until the 1980s that AAC began to emerge as a field in its own right. Rapid progress in technology, including microcomputers and speech synthesis, paved the way for communication devices with speech output, and multiple options for access to communication for those with physical disabilities.

AAC systems are diverse: unaided communication uses no equipment and includes signing and body language, while aided approaches use external tools. Aided communication methods can range from paper and pencil to communication books or boards to speech generating devices (SGDs) or devices producing written output.