Something you haven't smelled in years.

這氣味你已經好些年沒聞過了。

Somehow, the scent of glue immediately takes you back to your kindergarten classroom, and you spend the next couple of minutes wondering what happened to that kid who used to eat all that paste.

不知怎麼地，膠水的味道立刻帶你回想至幼稚園教室，然後你花了幾分鐘想著，那個曾經吃著漿糊的小孩究竟發生了什麼事。

You just experienced what's known as "odor-evoked autobiographical memory".

你剛剛經歷了的現象被稱為「氣味自主性記憶喚起」。

To put it simply, a smell made you remember something from your past, and it happened because of the way smells and memories are hard-wired into your brain.

不過這就只是一股讓你憶起過去事情的氣味，而會有這樣情況的發生是因為氣味與記憶在你腦中交互作用的結果。

There are lots of different cues, like sights or sounds, or even someone describing something or telling a story unrelated to your story, they can trigger memories.

有太多不同的線索，像視覺、聲音或甚至某人描述的事情，或你訴說的故事和你真正的故事不相關等，都會觸發你的記憶。

Memories links to smells are often stronger and more vivid.

氣味對記憶的連結通常更為強烈且鮮明。

And studies have shown that they also tend to be memories of your early life, often before you were 10 years old,

而且研究顯示它們通常容易是你小時候 10 歲之前的記憶，

which is weird, because adults usually experience what's known as a "reminiscence bump", when they don't remember much from before their adolescence.

而這樣的事實是奇怪的，因為成年人通常經歷的是「懷舊性記憶」，當他們無法憶起太多青少年以前所發生的事時，會發生這個現象。

But smells are really good at bringing those memories back.

然而氣味卻很容易喚起這些記憶。

These memories tend to be more perceptual rather than conceptual, so you remember a particular sensation rather than a bunch of facts about something that happened.

這些記憶傾向感性知覺而非理性知覺，因此你記得的是一個特定的感覺，而不是一堆已發生的事實。

And researchers have come up with some theories why memories triggered by smells are so odd.

且研究人員已經想出一些理論，探討受到氣味而觸發的記憶為何如此奇特的原因。

There's a big difference between the way your body handles sight, sound, taste, and touch, and the way it processes smells.

身體處理視覺、聽覺、味覺及觸覺的方法是有很不一樣的。

Those other senses are all routed through the thalamus, the part of your brain that sends them off into the appropriate processing centers.

其他感官都會通過丘腦，也就是大腦中負責處理這些感官知覺並送出資訊的中心。

But smells bypass all that.

但氣味會繞過這些路徑。

Once they're detected by receptors in your nose, the signal heads straight to your olfactory bulb, the smell-analyzing region in your brain.

一旦氣味被鼻子裡的接收神經察覺，訊號將會直達嗅球，也就是你腦中分析味道的區域。

And that area happens to be connected to the amygdala and hippocampus, which are parts of the brain that help handle memory and emotion.

之後它會與扁桃體和海馬體連線，這些腺體是腦中的一部分，負責掌管記憶及情緒。

So, it's possible that when you smelled that glue in kindergarten, the signal got tangled up with memories of building blocks and apple juice.

所以你幼稚園聞到膠水的味道時，訊號與帶有蘋果汁的記憶碎片是很有可能會糾結在一起的。

And when you smelled it again later, you remembered not just the glue but also some of the associated memories, like that weird kid who ate the paste.

然後當你再聞一次，你回憶起的不是只有膠水，而是與之相關的回憶，例如在吃膠水的奇怪小孩。

In 2013, a group of European psychologists tested this whole phenomenon using functional magnetic resonance imaging.

在 2013 年，一群歐洲的心理學家藉由核磁共振造影，測試這整個現象。

First, they presented the subjects with 20 different strong, specific odors, like garlic, whiskey, and leather.

一開始他們呈現 20 種帶有不同強烈氣味的物品，像是大蒜、威士忌還有皮革。

Then, for each person, they identified the two that elicited the oldest positive memories.

接下來他們對每個人指出兩種最能引導最舊記憶的味道。

Then, it was time to scan their brains.

接著，該掃描他們的大腦了。

Each subject was presented with their two experimental smells plus two generic control smells⏤flowers and citrus.

每個物品以兩種實驗性的氣味加上兩個一般性的控制味道——花及柑橘。

They were also shown some verbal cues, which were just the names and the smells projected onto a screen.

他們也會給予一些語言上的線索，而這個線索正是在螢幕投影出的名字及氣味。

The researchers found that both types of triggers tended to activate the regions of the brain associated with memory.

研究員們發現兩種形式的觸發點都傾向於啟動大腦連結記憶的區域。

But while the verbal cues lit up parts of the brain that were responsible for processing smells, the smells themselves were more strongly connected to emotional processing centers.

不過當有一些言語線索激發主管氣味的大腦部分時，氣味本身將強烈的連結情緒處理中心。

Some of the participants associated the smells with memories from before they were 10, while others remembered things from when they were between 10 and 20.

有一些受試者將這些氣味與來自 10 歲前的記憶互相連結，而其他人則憶起約 10 歲到 20 歲間的記憶。

And depending on which time frame the memories fell into, their brains tended to use different regions to recall them.

而且根據記憶進入大腦時的不同時間，傾向於使用不同的區域來憶起記憶。

The earlier memories lit up the orbital frontal cortex, which is connected to perception.

較早的記憶會激活眼眶額葉皮質——連結知覺的部位。

The later ones, on the other hand, tended to activate the left inferior frontal gyrus, which handles more conceptual memories.

而在另一方面，較晚的記憶傾向刺激左腦的前額葉腦迴區——掌管概念式記憶的區域。

So, can you use your nose's super powers to help you remember things for your next big exam?

所以你能夠使用你鼻子的超能力去幫助你記憶下一次大考的內容嗎？

Probably not!

可能是不行的！

Smells tend to evoke early, perceptive memories of events, not concepts.

氣味傾向喚起較早且知覺性的記憶片段，而不是概念。

So, the scent of glue might make you remember playing with construction paper in kindergarten, but your smell memory will not help you memorize Maxwell's equations.

因此膠水的氣味可能會使你想起在幼稚園時的美術紙，卻不能幫助你記憶馬克士威方程組。

Thank you for watching this SciShow dose, which was brought to you by our patrons on Patreon.

謝謝你收看由我們 Patreon 贊助人所帶來的 SciShow。

If you want to help support the show, you can go to patreon.com/scishow.

如果你真的想要幫助這個節目，可以前往以下的網站：PATREON.COM/SCISHOW。

And don't forget to go to youtube.com/scishow and subscribe if you just wanna keep learning things that are interesting.

如果你想持續學習有趣的新事物，記得前往訂閱 scishow 的 youtube 頻道。

'Cause I know you do.

我知道你一定想。