First Language Acquisition

To what extent are human infants predisposed to attend to speech sounds? This question has been addressed from a number of positions over the last few decades, with the answers becoming more complex as researchers learn more about how infants (and adults) analyze the speech stream, categorize speech sounds, and process running speech. This chapter looks at what infants start from as they begin to attend to the language around them and how they come to identify units within the stream of sound. What abilities do infants have at birth? Can they detect similarity and difference in successive speech sounds? When are they able to recognize previously heard units? Until children can recognize chunks of speech (words or phrases, for instance) as recurring from previous contexts, they cannot begin to attach meanings to them. The emphasis in this chapter is on how children first get in to language through exposure to and analysis of the speech stream.

In many cultures, adult speakers consistently differentiate how they speak according to the age of their addressees – infants, young children, older children, adults (see Chapter 2). Exaggerated affect in the voice, a wider pitch range, and steeper rises and falls in intonation mark off some speech as directed to infants, who appear to be particularly attentive to such modulations. Some researchers have proposed that such speech allows infants to attach affective meaning to vocalizations early in their exposure to language (Bloom 1997; Fernald 1992). The modifications adults adopt also serve to display shorter chunks of the speech stream than one might hear in adult-to-adult speech (shorter utterances, clearly articulated, and typically separated by pauses). They also highlight recurring words and consistently display new information, for instance, in either initial or final position in the utterance. The adjustments that adults make to different-age addressees are generally geared to children's levels of comprehension, and have the effect of breaking up the speech stream into what may well be more manageable chunks for analysis.

Tackling the speech stream: Extracting forms

Whether children listen to the speech addressed to them or to the speech around them, they are faced with some critical problems. One is the segmentation problem – how to go about identifying units (phrases, words, morphemes, sound segments) in the speech stream when they have no reason to break it up at any particular point.