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  • There's no better poker face than that of the fox squirrel.

  • These animals just do not produce facial expressions.

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

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

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

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

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

  • Could it open a window into squirrels' emotional worlds?

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

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

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

  • Squirrels love walnuts.

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

  • It's actually squirrel for "Back off."

  • "This is my nut."

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

  • And this is key.

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

  • Then she changed things up.

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

  • The squirrels were not amused and the tail flagging began.

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

  • Finally, she locked the box.

  • Flag, flag, and flag.

  • The squirrels got aggressive, a hallmark of frustration.

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

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

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

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

  • See?

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

  • Delgado's hypothesis is that frustration might actually be beneficialthat pitching a fit might sometimes be just what squirrelsand peopleneed to figure things out.

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

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

  • Or how Christmas trees have sex.

  • Deep Look has the answers.

  • So subscribe.

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

  • Thanks for watching.

There's no better poker face than that of the fox squirrel.

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