爲什麼有時候總感覺有人在盯着你看?

Something makes you turn and see someone watching you. Perhaps on a busy train, or at night, or when you're strolling through the park.
也許是在擁擠的火車上，或是在公園漫步的某個晚上，你會時不時回頭看看，因爲總感覺有人在看着你。

How did you know you were being watched? It can feel like an intuition which is separate from your senses, but really it demonstrates that your senses – particularly vision – can work in mysterious ways.
你怎麼知道有人在看你？這種感覺更像是獨立於感官意識的一種直覺，但是它確實也證實了你的感官，尤其是視覺能以一種神奇的方式運作。

Intuitively, many of us might imagine that when you look at something with your eyes, signals travel to your visual cortex and then you have the conscious experience of seeing it, but the reality is far weirder.
直觀上來說，許多人可能會想象當你看見某件東西時，視覺信號會傳遞到視覺皮層，然後你就能視物，然而實際遠不止此。

Once information leaves our eyes it travels to at least 10 distinct brain areas, each with their own specialised functions.
一旦信息離開我們的眼睛，它就會被傳送到至少10個不同功能的腦區。

Many of us have heard of the visual cortex, a large region at the back of the brain which gets most attention from neuroscientists.
許多人可能聽說過視皮層，它位於大腦後部，是神經科學家重點關注的區域。

The visual cortex supports our conscious vision, processing colour and fine detail to help produce the rich impression of the world we enjoy.
視覺皮質通過加工顏色和細節來幫助我們產生對這個世界的印象，從而使我們能夠視物。

But other parts of our brain are also processing different pieces of information, and these can be working away even when we don't – or can't – consciously perceive something.
然而大腦的其他區域也在處理着不同的片段信息，而且這種處理甚至能在我們沒有意識到的情況下進行。

The survivors of neural injury can cast some light on these mechanisms. When an accident damages the visual cortex, your vision is affected. If you lose all of your visual cortex you will lose all conscious vision, becoming what neurologists call 'cortically blind'.
神經受損的倖存者能闡明這些機體原理。當一起事故損害了你的視覺皮質，你的視力就會受影響。如果你失去了所有的視覺皮質，那麼你就會失明，成爲神經科學家所說的“皮質盲”。

But, unlike if you lose your eyes, cortically blind is only mostly blind – the non-cortical visual areas can still operate.
但是，這跟你失去眼睛不一樣，皮質盲會導致跟皮質有關的視力受損，非皮質的視覺不會受影響。

Although you can't have the subjective impression of seeing anything without a visual cortex, you can respond to things captured by your eyes that are processed by these other brain areas.
雖然沒有視覺皮層，你不能產生視覺的主觀印象，但是你能對眼睛捕獲到的信息進行反應，因爲它們是大腦的其他區域處理的。

One study showed that we can detect that people are looking at us within our field of view – perhaps in the corner of our eye – even if we haven't consciously noticed. It shows the brain basis for that subtle feeling that tells us we are being watched.
一項研究表明，即使我們沒有意識到，我們視線所及的東西還是能被看到。這表明了大腦產生的這種微妙感覺告訴了我們正在被注視。

So when you're walking that dark road and turn and notice someone standing there, or look up on the train to see someone staring at you, it may be your nonconscious visual system monitoring your environment while you're conscious attention was on something else.
所以當你走夜路時回頭發現後面有人，或者在火車上注意到有人看你，這些無意識的視覺系統正在監測你周圍的環境，而你的注意力顯然在其他地方。

It may not be supernatural, but it certainly shows the brain works in mysterious ways.
這並非是超自然現象，但是這表明了你的大腦的確在以一種神奇的方式運轉。