For example, the sense that tells you you're feeling hot or cold, the sense that tells you you're out of breath, and the sense of balance.

舉例來說，你可以感知冷熱，或是感到喘不過氣，還有平衡感。

We don't consciously experience the raw information all these senses generate, because the brain is constantly engaged in the act of perception—the analysis, synthesis and interpretation of all that data.

我們不自覺地感受所有感官產生的原始資訊，因為大腦持續不斷參與知覺的行為——分析、合成和判讀所有訊息。

Perception can utilise what's known as bottom-up processing, whereby the brain relies on analyzing sensory data.

感知可以利用所謂的「由下而上處理歷程」，而大腦就是靠這個過程分析感官的訊息。

But certain perceptions are produced in a different way, by top-down processing—instead of relying just on sensory data, the brain calls on past experiences to make a best guess as to what might be there.

但是特定的感知是由不同方式所產生——藉由「由上而下處理歷程」，大腦不再只仰賴感官資訊，而是利用過往的經驗猜測所看到的東西。

In certain situations though, this type of processing results in mistakes.

但是在某些情況下，這類的處理歷程會導致錯誤。

Like this —you're probably seeing two different colours here, but in fact there's only one.

舉這個畫面為例，你看見的可能是兩種不同顏色，但實際上只有一種顏色而已。

Based on past experience—that surfaces in brighter light are darker than they appear, and surfaces in shadow are lighter.

根據過去的經驗，在明亮處的表面會看起來比實際上暗，而在陰影處的表面會看起來比較亮。

The brain expects that there should be two shades, and so that's what it puts into the virtual model it's creating.

大腦預測圖上應該要有兩個陰影，因而創造出虛擬的模型。

This top-down processing accounts for a number of human perception traits.

由上而下處理歷程負責一些人類感知的特徵。

We very often see faces, because we're hardwired to tune into them.

我們很常看見臉，因為我們本能地將事物調整成臉的形狀。

The fact that we're all living in our own virtual recreations of the world is revealed most sharply by cases of people with malfunctioning perception, known as agnosia.

我們都生活在自己創造的虛擬再現世界，感官失常俗稱「失認症」的人，清楚地揭發這項事實。

It's a general term that covers many different conditions.

「失認症」是涵蓋許多不同疾病的總稱。

What they all have in common is that the senses are still working perfectly.

而感官仍然正常運作是這些疾病的共通點。

The brain is receiving the same information it always did, but its ability to process, interpret, and recognize is damaged.

大腦仍舊接收同樣的資訊，但是處理、判讀和辨識的功能有所缺損。

Someone suffering from prosopagnosia, for example, has serious difficulty recognizing people by looking at their faces, but could still recognize them instantly from the sound of their voice.

舉例來說，患有「臉盲症」的人，無法藉由看臉辨識出其他人，但是仍可以馬上由聲音辨別他人。

In extreme cases, sufferers can't recognise their own image in a mirror.

更嚴重的情況是，患者無法在鏡子中辨識出自己的影像。

A person with akinetopsia is able to perceive objects normally when they're still, but can't recognise, or make sense of anything that's moving.

患有「運動失認症」的人，在靜止不動時通常可以察覺到物體，但是無法辨識或了解是什麼東西在移動。

When someone with auditory verbal agnosia hears words, they just hear meaningless noises, so they can't have a conversation.

當「言語失認症」患者聽話時，他們聽到的僅是無意義的噪音，所以無法展開談話。

But it's only the hearing of words that's affected—they can still talk, read and write.

但是他們受影響的僅有聽覺，所以還是可以說話、閱讀和寫作。

So, our ability to navigate the world is entirely dependent on the complex mechanisms, which interpret all the noise our senses make and give it meaning.

我們駕馭世界的能力完全依靠複雜的機制，這個機制判讀我們感官產生的所有雜音並給予意義。

Or, as the famous neurologist Oliver Sacks put it: "Every act of perception is to some degree an act of creation."

如同著名的神經科醫生 Oliver Sacks 所說：「知覺的每一個行動，在某種程度上就是一種創造。」

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感謝你的收看。

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記得訂閱並開啟小鈴鐺接收最新影片的消息。

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下次見！