On the role of language in children's early understanding of others as epistemic beings

In the study reported here, Japanese-speaking children aged 3–6 were confronted with making choices based on conflicting input from speakers who varied in the degree of certainty and the quality of evidence they possessed for their opinions. Certainty and evidentiality are encoded in Japanese both in high-frequency, closed-class, sentence-final particles and also in low-frequency, mental state verbs. Our results suggest that children are able to make use of information encoded in the sentence-final particles earlier than information encoded in verbs, and that understanding of speaker certainty precedes understanding of quality of evidence. Furthermore, although the results generally support the position that children's overall understanding of epistemic vocabulary correlates with their understanding of false-belief, understanding of the sentence-final particles tested did not correlate with false-belief understanding. We argue that understanding of speakers’ epistemic states as communicated by sentence-final particles prior to the fully-representational understanding of (false) belief should be taken as an indication of children's inchoate understanding of other's mental states.