Children's understanding of certainty and evidentiality: advantage of grammaticalized forms over lexical alternatives.

In verbal communication, the hearer takes advantage of the linguistic expressions of certainty and evidentiality to assess how committed the speaker might be to the truth of the informational content of the utterance. Little is known, however, about the precise developmental mechanism of this ability. In this chapter, we approach the question by elucidating factors that are likely to constrain young children's understanding of linguistically encoded certainty and evidentiality, including the types of linguistic form of these expressions, namely, grammaticalized or lexical forms.