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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.
也许是在拥挤的火车上，或是在公园漫步的某个晚上，你会时不时回头看看，因为总感觉有人在看着你。
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.
你怎么知道有人在看你？这种感觉更像是独立于感官意识的一种直觉，但是它确实也证实了你的感官，尤其是视觉能以一种神奇的方式运作。
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.
直观上来说，许多人可能会想象当你看见某件东西时，视觉信号会传递到视觉皮层，然后你就能视物，然而实际远不止此。
Once information leaves our eyes it travels to at least 10 distinct brain areas, each with their own specialised functions.
一旦信息离开我们的眼睛，它就会被传送到至少10个不同功能的脑区。
Many of us have heard of the visual cortex, a large region at the back of the brain which gets most attention from neuroscientists.
许多人可能听说过视皮层，它位于大脑后部，是神经科学家重点关注的区域。
The visual cortex supports our conscious vision, processing colour and fine detail to help produce the rich impression of the world we enjoy.
视觉皮质通过加工颜色和细节来帮助我们产生对这个世界的印象，从而使我们能够视物。
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.
然而大脑的其他区域也在处理着不同的片段信息，而且这种处理甚至能在我们没有意识到的情况下进行。
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'.
神经受损的幸存者能阐明这些机体原理。当一起事故损害了你的视觉皮质，你的视力就会受影响。如果你失去了所有的视觉皮质，那么你就会失明，成为神经科学家所说的“皮质盲”。
But, unlike if you lose your eyes, cortically blind is only mostly blind – the non-cortical visual areas can still operate.
但是，这跟你失去眼睛不一样，皮质盲会导致跟皮质有关的视力受损，非皮质的视觉不会受影响。
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.
虽然没有视觉皮层，你不能产生视觉的主观印象，但是你能对眼睛捕获到的信息进行反应，因为它们是大脑的其他区域处理的。
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.
一项研究表明，即使我们没有意识到，我们视线所及的东西还是能被看到。这表明了大脑产生的这种微妙感觉告诉了我们正在被注视。
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.
所以当你走夜路时回头发现后面有人，或者在火车上注意到有人看你，这些无意识的视觉系统正在监测你周围的环境，而你的注意力显然在其他地方。
It may not be supernatural, but it certainly shows the brain works in mysterious ways.
这并非是超自然现象，但是这表明了你的大脑的确在以一种神奇的方式运转。
