Text and Data Mining valid from 2019-01-13
First Online: 13 January 2019
Compliance with Ethical Standards
: This research was supported by grants from the Key Research Base of the Humanity and Social Sciences Section of the Ministry of Education of China (16JJD840001) and the General Program of the Humanity and Social Sciences Section of the Ministry of Eduction of China (18YJA190009).
: The authors declare that they have no conflict of interest.
: The study was approved by the review boad of Shanghai Normal University.
: Informed consent was obtained from all children and their parents.