Meaning of 童心 in Japanese

童心にかえってもう一度やり直しましょう。
I will mentally return to childhood and do it all over again.

彼女は児童心理学専攻だ。
She majors in child psychology.

児童心理学者の中には、親はもっと子供と遊んでやり、考えさせる問題を与えてやるべきだ、と考える人が多い。
Many child psychologists think that parents should play with their children more often and give them problems to think about.