Speakers often manipulate their articulations in such a way that their articulatory consequences are more clearly conveyed to listeners, especially in various contexts where their “normal” articulations may result in misperception of the intended messages. The current experiment explored at what developing-stage Japanese-speaking children acquire the ability to execute this sort of articulatory manipulation. We found that the children who are 2 or 3 years old (2;6~3;5), at least some of them, can indeed adjust their articulations, when they are asked to repeat what they uttered. We also explored the relationship between this ability to speak clearly and the development of “the theory of mind,” with the hypothesis that speaking clearly entails an ability to be able to guess what it is like for listeners to receive acoustic signals of the normal, unadjusted speech. The experiment shows, however, that there was no clear evidence for the correlation between the ability to speak clearly and the acquisition of the theory of mind.

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