Whether the eyes are "the windows of the soul" is debatable;
they are intensely important in interpersonal communication is a __1__
fact. During the first two months of a baby's life, the stimuli that __2__
produces a smile is a pair of eyes. The eyes need not to be real: a __3__
mask with two dots will produce a smile. Significantly, a real human
face with eyes covered will not motivate a smile, or will the sight of __4__
only one eye when the face is presented on profile. This attraction to __5__
eyes opposed to the nose or mouth continues as the baby matures. __6__
In one study, when American four-year-old were asked to draw __7__
people, 75 percent of them drew people with mouths, and 99 percent __8__
of them drew people with eyes. In Japan, furthermore, where babies __9__
are carried on their mother's back, infants do not acquire as much
attachment to eyes like they do in other cultures. As a result, __10__
Japanese adults make little use of the face either to encode or decode
meaning.

答案及解析:
1.^they-that
分句后的分句应有它独立的主谓结构，正像它前面的结构一样。而后半句的谓语是is，表语是fact，主语似乎是缺失的，因此在they前面加上that就构成了主语从句作为这半句的主语。

2.stimuli-stimulus
stimuli看似单数实则是stimulus的复数形式，因此应改为stimulus。

3.to-/
这里的need作情态动词，因此删去to。

4.or-nor
并列的否定，用否定形式nor表示倒装。

5.on-in
in profile表示 “侧面，从侧面”。如：
The painting shows her in profile。

6.^opposed-as
opposed前应使用连词as引导比较分句。

7.old-olds
由谓语的复数形式可以看出这里需要用复数形式four-year-olds。

8.and-but

9.furthermore-however
上一句话指明美国文化中眼睛的重要性，而这一句话似乎指出日本文化中眼睛并不具有同样的重要性，因此两句话的关系是转折而不是递进。

10.like-as
句子中有一个as……as比较结构。