The development of lexical tone perception and production was investigated in sixty normally developing Cantonese-speaking children (aged 2 to 5 years). Overall, the accuracy of tone identification improved from 2 to 5 years of age. Children's production of lexical tones was measured through phonetic transcriptions. A particular tone was judged to have been acquired when transcription accuracy was 90% or better. On the basis of this criterion, the acquisition of tone production was completed by 4 years of age.
Bibliographic reference. Ciocca, Valter / Ip, Vivian W.-K. (2008): "Development of tone perception and tone production in Cantonese-learning children aged 2 to 5 years", In INTERSPEECH-2008, 623.