But how do you know what you're seeing is real? Can you really trust your eyes?

但你怎麼知道你看到的東西是真的呢？你真的能相信雙眼看見的一切嗎？

Take for example these two grey rectangular columns, both of which are different shades of grey. Or are they?

舉個例來說，畫面上的兩條灰色四方型柱狀圖你覺得它們一樣灰？還是不一樣灰呢？

It turns out that they're the exact same.

答案是一樣。

And yet, even after knowing the illusion is there, your eyes refused to see them as the same.

就算你知道這種假象的存在，你的眼睛還是無法將他們視為相同 。

Introducing colors produces the same result.

即使添加更多顏色，結果還是沒有改變。

I promise, no trick photography or editing effects have been applied.

我保證，這絕對不是利用攝影技巧或是修片效果搞出來的。

In fact, if you look up the Munker-White illusion, you'll come across many more examples.

事實上，如果你查查「視覺假象」一詞你就會得到更多類似的例子。

Examine them in Photoshop and you can see that the colors are the exact same.

把這些圖抓到photoshop上驗證一下，你就會發現這些顏色其實是同樣的。

A similar effect can be seen with this checkerboard illusion.

有個相似的效果叫做「棋盤錯覺」。

Tile A clearly seems darker than tile B. But you know better by now, right?

A 磚的顏色看起來明顯比 B 磚深，但這次你知道答案，是吧？

Even though your eyes can't see it, you know when I removed the surrounding imagery

即使眼睛看不出來，但只要把旁邊的磁磚移開。

the tiles will be the same color. So what's going on here?

A 和 B 的顏色就會一樣。這到底是怎麼一回事呢？

The truth is that scientists don't fully understand this phenomenon, and there are many complex biological and neurological factors taking place.

事實上，科學家尚未完全瞭解此現象為何發生，這種現象發生時牽連著許多複雜的生物學、神經學的誘因。

Ultimately, our brains judge color and brightness in context.

最後才由我們的大腦來分辨背景中的顏色和深淺。

In other words, our brains compare the surrounding environment in order to create our perception.

換句話說，我們的大腦會先將目標物與周遭環境做比較，然後製造出我們對外界的感知。

The purpose of our senses or eyes in this case is not to provide us with an absolute color or physical property of our external reality,

在這種情況下，我們的五感和五官所扮演的腳色不是提供我們現實生活中的絕對色度，或是物理性質。

but to interpret what we see as efficiently as possible in order to interact with our environment most appropriately.

而是演繹我們看見的東西最有可能是甚麼，如此一來才能夠與環境達到最佳的互動。

The tile illusion takes advantage of this phenomenon.

而色磚錯覺就是利用這種現象的特性。

Our brains know that shadows make objects look darker, as a result the brain compensates by interpreting the tile as being lighter than it appears until we take the shadow away.

因為我們的大腦知道陰影會使物體看起來更黑，所以大腦透過提高色磚亮度的演繹方式來使其互補，這樣的演繹方式會持續作用，直到我們把陰影拿走。

Perhaps, the most blatant example is this gradient.

或許最典型的例子就是漸層效果。

The middle bar is simply one color.

中間的色條其實是單一色的色條。

Remove the background gradient and it becomes obvious. Once again, the darkness of the background has affected our perception of the bar's color.

只要移開漸層背景，你也能明顯分辨。同樣的手法，黑色背景影響了我們對色條的感知。

Our perception is relative.

我們對外在的感知是透過比較來分辨的。

So do you still trust your eyes?

現在你還相信你看見的一切嗎？

Got a burning question you want answered?

現在的你是不是有不解的地方想發問呢？

Ask it in the comments, or on Facebook and Twitter and subscribe for more weekly science videos.

在下方留言處留下你的問題，或是在我們的臉書或推特專頁上留言，最後別忘了訂閱我們的頻道，每周都有學不完的科學小知識喔。