Whether other instinctual forces exist, such as a rough-and-tumble "play" system, is also being investigated.
是否还有其他如杂乱无章的「游戏」系统的本能存在，目前还在研究当中。
He is now able to play rough and tumble with the other kids.
现在他可以粗暴地摔倒其他孩子了。
Children tumble over each other in play.
孩子们玩耍时相互连身翻滚。
Children tumble over each other in play.
孩子们玩耍时相互连身翻滚。
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