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<Paper uid="W97-0506">
  <Title>Augmented and alternative NLP techniques for augmentative and alternative communication</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> The work described in this paper concerns the communication needs of people who cannot speak because of motor disabilities. It is possible to build prosthetic devices for such users by linking a suitable physical interface with a speech synthesizer, so that text or other symbolic input can be converted to speech. However, while speech rates in normal conversation are around 150-200 words per minute (wpm), and skilled typists can achieve rates of 30-40 wpm 1, conditions which impair physical ability to speak usually cause more general loss of motor function and typically speech prosthesis users can only output at best 10-15 wpm using a keyboard, with much lower rates if direct letter selection is not possible. This prevents natural conversation, not simply because of the time which is taken but because the delays completely disrupt the usual processes of ISome typists can copy text much faster than this, but constructing text takes more time, even with informal text such as email. Some people who spend a lot of time contributing to online forums have reported typing speeds which are considerably higher than this range, but they still cannot approach normal conversation speeds.</Paragraph>
    <Paragraph position="1"> turn-taking. Thus the other speaker finds it hard to avoid interrupting the prosthesis user.</Paragraph>
    <Paragraph position="2"> This problem can potentially be alleviated in two ways: by improving the design of the physical interface (keyboard, head-stick, head-pointer, eye-tracker etc) or by minimizing the input that is required for a given output. The research described here concentrates on the latter aspect, although the utility of various techniques is partially dependent on the interface.</Paragraph>
    <Paragraph position="3"> Techniques which have been used in augmentative and alternative communication (AAC) often involve the use of alternative symbol systems for input, in particular Minspeak (Baker, 1982). However, the work reported here was prompted by the needs of an individual who has lost the ability to speak due to amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease). Such users would prefer to continue using their original language, rather than to learn an alternative symbol system. Several commercial AAC systems which take text input exist, but we found that these had a variety of drawbacks for our user. In particular, most are dedicated to speech output and cannot be used to aid writing text or email. There are also limitations in compatibility with particular software or hardware, and restrictions in the physical interfaces. A system was developed at CSLI which would run on a standard laptop while still allowing the use of other software (email, Web browser etc).</Paragraph>
    <Paragraph position="4"> The initial version of this system incorporates word prediction, as describec~ in the next section, and also a small number of fixed text utterances, accessible via dedicated keys or menus. Experience with this suggested that an approach which allowed for more flexible combination of fixed and free text might have advantages. This is outlined in SS3.</Paragraph>
  </Section>
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