你的眼睛一旦贴着桌子边缘看它，你就会发现它不再呈现出一个图形的样子，从外观上来看，它变成了一条直线。

As soon as you look at it with your eye on the edge on the table, you will find that it ceases to appear to you a figure, and that it becomes in appearance a straight line.

youdao

You put a child on one side of the mountains and you ask him to draw it, and a four- or five-year-old can do it easily, but then you ask him to draw it as it would appear from the other side and children find this extraordinarily difficult.

你让孩子在模型的一边,要求他把自己看到的三山模型画出来,四五岁的儿童便能够轻易做到,但是,如果你要求儿童画出,从模型另一边看过去的样子,儿童就会觉得非常困难

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