Speech Tools and CALL for Literacy Tutoring

In this chapter we are concerned with the use of CALL technology for literacy and (second) language learning automatic tutoring. In particular we shall be concerned with the use of text-to-speech synthesis, or TTS, as a tool for second language learning and for literacy tutoring particularly in presence of language disabilities. We will present a number of language learning applications in which TTS plays a fundamental role: for instance, TTS can be used to foster awareness of the contrastive features of the phonology of the second language. It can be used to power a speaking tutor for any self-instructional system and to voice feedback on an exercise. It can be used as a reader for dictation exercises where the need is to vary voice quality and speaking rate. TTS can also be used to give students hints about a listening comprehension task and other drills. We shall illustrate these various roles for TTS in computer-assisted language learning (CALL). Of course, we do not assume that synthesized speech is the only way to cope with oral language practice. In general, having a human tutor present this kind of activity guarantees much better results than TTS. The question is whether a human tutor may always be available when the student needs one. Because access to a human tutor is not always possible, TTS is worth pursuing. Moreover, there is at least one case in which a computer-based speaking tutor constitutes the only viable alternative to the human tutor: when mimicking the evolving levels of speaking proficiency in the second language (L2), also known as levels of interlanguage (Selinker 1992), as will be explained further on. Finally, if feedback is generated on the fly – through automatic means such as filling template slots with words from an exercise – then use of synthesized voice is the only practical way to avoid having to predict and record all possible combinations of words in templates. Besides spoken and written text comprehension and sound-grapheme correspondences, an important and related goal of second language learning is acquiring the lexicon of the language. Indeed, lexical learning is the first challenge a second language student has to face.