These animals just do not produce facial expressions.

這些動物壓根沒有任何臉部表情。

For a squirrel, it's all about that tail.

對松鼠來說，尾巴才是重點。

When a predator is around, the squirrel doesn't snarl.

敵人逼近時，松鼠並不會發出吼叫。

Instead, it whips its tail back and forth to look big and fearsome.

而是會前後擺動尾巴，讓自己看起來身形巨大嚇人。

Researchers call this s-shaped movement "flagging," and it means the squirrel feels really threatened.

研究人員把這種 S 型的動作稱為「揮旗」，意味著松鼠感到威脅。

At the University of California, Berkeley, animal behaviorist Mikel Maria Delgado wondered what else she could learn from watching squirrels flag their tails.

在加利福尼亞大學柏克萊分校，動物行為專家 Mikel Maria Delgado 好奇松鼠尾巴還能告訴她什麼。

Could it open a window into squirrels' emotional worlds?

這是否能告訴我們松鼠的情緒？

For instance, do squirrels get frustrated, like we do?

舉例來說，松鼠會像我們一樣感到失望嗎？

So she lured some of the squirrels that live on campus down from the trees.

所以她把校園裡的一些松鼠從樹上引下來。

She taught them how to open a box to find a walnut inside.

她教他們如何打開盒子、找到裡面的胡桃。

Squirrels love walnuts.

松鼠很愛胡桃。

That little two-step he's doing… it kind of looks like "Woo hoo! I'm about to get a nut!"

牠那兩個擺動 …… 好像在說「耶比！我要有胡桃了！」

It's actually squirrel for "Back off."

但其實是松鼠語的「滾開」。

"This is my nut."

「這胡桃是我的。」

Once the squirrels learned how to open the box, Delgado trained them to expect a walnut each time they looked inside.

松鼠一旦學會開盒子，Delgado 接著讓牠們習慣在盒子裡看到胡桃。

And this is key.

這很關鍵。

Because frustration is usually defined as not getting what you expected.

因為失望往往代表著沒有得到預期的結果。

Then she changed things up.

然後她改變遊戲方式。

For some squirrels, she replaced the nut with corn, which squirrels don't like as much.

她把一些松鼠的堅果換成玉米，松鼠沒那麼喜歡玉米。

The squirrels were not amused and the tail flagging began.

松鼠不是很開心，又開始揮動尾巴了。

Other times, she left the box completely empty: they flagged their tails even more.

其他時候她根本沒在盒子裡裝東西，牠們的尾巴揮得更用力了。

Finally, she locked the box.

最後她把盒子鎖上。

Flag, flag, and flag.

揮、揮、揮。

The squirrels got aggressive, a hallmark of frustration.

松鼠開始動手動腳，看起來很失望。

The question is, if squirrels do it, and we do it, why do we get frustrated?

問題在於，如果松鼠和我們都會，我們為什麼會有失望情緒？

Why is it useful, from an evolutionary point of view?

從演化的觀點來看，為什麼這種情緒是有用處的？

Here's one possible answer: the frustrated squirrels aren't just blowing off steam.

一個可能的解答是：失望的松鼠不只是單純發洩怒氣。

They're gathering up the energy to brute-force a new solution -- kind of like kicking the vending machine when it eats your dollar.

牠們在累積力氣用蠻力解決，有點像是你在踢把你零錢吃掉的販賣機。

See?

看到了嗎？

They're trying different ways to open up the box.

牠們在試著用不同的方式打開盒子。

Delgado's hypothesis is that frustration might actually be beneficial… that pitching a fit might sometimes be just what squirrels – and people – need to figure things out.

Delgado 的假設認為失望其實有益，發洩怒氣或許就是松鼠和人類解決問題所必需的。

If you've wondered about the emotional life of squirrels -- and really, who hasn't?

如果你好奇過松鼠都在想些什麼，說真的誰沒想過呢？

Then maybe you've also asked why banana slugs are so slimy.

或許你也好奇過為什麼蛞蝓黏糊糊的。

Or how Christmas trees have sex.

或是聖誕樹交配的方式。

Deep Look has the answers.

Deep Look 頻道有這些解答。

So subscribe.

所以訂閱吧！

And let us know what you think in the comments below.

留言告訴我們你的想法。

Thanks for watching.

感謝收看。