1. Your brain is so sensitive in picking up facial traits...
be sensitive in 和 be sensitive to，意思有别。前者是：在...方面灵敏；后者是：对……过敏
例如：
This balance is very sensitive in weighing. 这个天平称重很灵敏。（在……方面灵敏）
This tooth is sensitive to cold.   这颗牙对冷过敏。（对……过敏）
2. ... very minor difference ... make you see him or her as different.
这个句子的主语应为differences(复数)，谓语是make(使)。as different之后省略了as others.即：make you see him or her as different as others.
……细小差异也会使你看到其（与别人）不同。
3. be sensitive in： 在......方面灵敏；在......方面敏感，均可。原句仍然翻译为“在……方面敏感”。
4. 固定句式：see + 宾语 + as + 名词/形容词，as短语做宾补。意为：把...看作是什么/如何。例如：
I see it as accurate. 我把它看作是精确的。
We see it as a tragedy. 我们把这看作是一个悲剧。
You know it’ll break someday, so from the beginning, see it as already broken. 你知道它总有一天会碎，所以从一开始，你就把它看作已经碎了。
所以，...see him or her as different 意为“...把他或她看作是不同的”。
5. 句中 difference 既然用单数，前面缺少了冠词 a，此外，后面的谓语是 make，故建议改用复数或加不定冠词。如：
...even a very minor difference in how a person's eyes, ears, nose, or mouth are placed in relation to each other makes you see him or her as different.
6. 我给你分析一下句子成分：
Very minor difference in how a person's eyes, ears, nose, or mouth are placed in relation to each other makes you see him or her as different.——这是一个完整的句子。
(1) Very minor difference：主语
(2) makes：谓语
(3) you see him or her as different：复合宾语
(4) in how a person's eyes, ears, nose, or mouth are placed in relation to each other：介词短语作定语，修饰difference。名词性从句how a person's eyes, ears, nose, or mouth are placed in relation to each other是in的宾语。
(5) in relation to each other意为“器官彼此间的关系”，修饰are placed。不是指“每个人”，前面的a person才是指每个人。句中的 in relation to each other 修饰 are placed。
a person's eyes, ears, nose, or mouth are placed in relation to each other. 一个人的眼睛、耳朵、鼻子或嘴巴彼此有关联地放置一起。