So, what they do is, the first time they might scratch at the bars, push at the ceiling, dig at the floor, howl, etc.

起初小猫可能会抓栏杆，推顶棚，挖底板，吼叫等等。

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The lever gets them out of the box, but after more and more trials they stopped scratching at the bars, pushing at the ceiling and so on.

杠杆让它们逃出迷笼，但在经历多次尝试之后,它们不再抓栏杆，不再推顶棚。

耶鲁公开课 - 心理学导论课程节选