Page 471 - Biomedical Engineering and Design Handbook Volume 2, Applications

TECHNOLOGY AND DISABILITIES 449

of text or a menu appears (Lazzaro, 1999). This feature allows the user to automatically have pop-up
window and dialog boxes read to her. Screen readers can typically be set to speak by line, sentence,
or paragraph.
For Windows-based computers, the majority of commercial products include both a voice
synthesizer and a software-based screen reader to provide access. Many of these bundled software
programs also work with computer soundboards to generate high-quality synthetic speech. Tactile
(Braille) display of screen information is the other major alternative for screen readers. This requires
the use of a translator program to convert from text characters to Braille cell dot patterns. Computer
output systems utilize either a refreshable Braille display consisting of raised pins or hard copy via
Braille printers. Refreshable Braille displays consists of 20, 40, or 80 separate cells. Rather than the
standard six-cell Braille used for print materials, a unique eight-dot cell format is available in which
the seventh and eighth dots are used for indicating the location of the cursor and to provide single-cell
presentation of higher-level ASCII characters. The latter feature is necessary since the normal 6-cell
Braille display can only generate 64 permutations and full ASCII has 132 characters. Braille embossers
produce hard copy (printed) output. Cook and Polgar (2008) describe a number of commercial
approaches to screen readers with speech and Braille output as well as embossers for hard copy.

15.4 AUGMENTATIVE AND ALTERNATIVE COMMUNICATION

The term augmentative and alternative communication (AAC) is used to describe any communication
that supplements speech. When someone is unable to speak and/or write so that all current and potential
communication partners can understand them, then an AAC system is required. Communication
requiring only the person’s own body, such as pointing and other gestures, pantomime, facial expres-
sions, eye-gaze and manual signing, or finger spelling is called unaided communication. Aided AAC
may be either electronic or nonelectronic and includes a pen or pencil, a letter or picture communi-
cation board, a computer, a cell phone, and an electronic speech generating device (SGD).
Humans communicate in many ways, including speaking and writing, for example face to face,
on the phone, and across the Internet. Writing includes drawing, plotting, graphing, and mathemat-
ics. Light (1988) describes four purposes of communicative interaction: (1) expression of needs and
wants, (2) information transfer, (3) social closeness, and (4) social etiquette. Expression of needs and
wants allows people to make requests for objects or actions. Information transfer allows expression
of ideas, discussion, and meaningful dialogue. Social closeness connects individuals to each other,
and social etiquette establishes cultural formalities in communication. For example, students will
speak differently to their peers than to their teachers.

15.4.1 Needs Served by Augmentative Communication
In considering communication needs, we address three perspectives: individuals with developmental
disorders; individuals with acquired conditions, and individuals with degenerative conditions. The
focus of AAC interventions may vary across these groups. AAC interventions for children with
developmental disabilities require integration into the child’s daily experiences and interactions that
take into account what we know about child development (Light and Drager, 2002). Adults with
acquired disabilities such as traumatic brain injury (TBI), aphasia, and other static conditions may
require the use of AAC interventions as part of the rehabilitation process (Beukelman and Ball,
2002). Persons who are recovering from injury or disease often experience changing levels of motor,
sensory, and/or cognitive/linguistic capability that can benefit from the use of aided AAC.

15.4.2 Characteristics of Augmentative Communication Systems
Since speech allows communication at a rapid rate, between 150 and 175 words per minute (Miller,
1981), an individual using an AAC system must be as rapid as possible. In all AAC systems, some