Onions, Emotions, and Why We Cry

Have you ever wondered why we cry? In today's episode of SciShow, Hank gives us the answer, covering different types of tears and whether we are the only species to get all teary eyed during the final scene of a good movie.
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[MrNorris]

I used to cry when my dad chopped onions. I miss onions. He was a good dog.

[BinkieMcFartnuggets]

You can experience all three tears if you're murdering an onion you used to love.

[LucysCorsetry]

I wear RGP contacts and it greatly helps prevent onion-caused weeping, but if *any* piece of sand or dust gets lodged underneath my lens, it feels like the apocalypse in my eyeball.

[MikeGoesBoom]

Feasting on the tears of my enemies has always been my primary source of Protein

[TongueFlagpole]

That was beautiful, Hank. ~ *sniff* ~

[KustomFu]

please do "Why do songs get stuck in our heads"

[chefkendranguyen]

I did not know there are 3 types of tears, interesting.

[SatinFoxx]

"Emo tears",   the latest band from the label that brought you: "I bleed rainbows"
 and "I scream 'cuz mommy didn't tell me she loved me this morning"

[zoeirons]

Oddly enough upon finishing watching this video I poked myself in the eye with my finger and experienced reflex tears. 

[danielkim]

I tear up when I yawn. Can anyone tell me why?

[tiomthytatum]

dude ill admit youare really smart, and you know a lot. thanks for sharing, you know what they say, can't learn enough :) keep showing those videos

[LuckyAssult]

I remember when i came out to my parents and grand parents, and they said that they supported me and did not juddge. I was so revealed to hear that, that i broke down into tears of joy. I still cry abit thinking about that moment.

[sydniesterk]

Your brothers books made me cry for hours :'(

[fakjbf]

Before watching the video: I would guess that tears evolved as a social signal. They are extremely obvious and easy to pick up on, and are usually reserved for the extremes of emotions, which were very helpful to communicate to other members of the group in the tens of thousands of years before we had real language.

EDIT: Yay, I was right!

[jhark]

I was going to suggest this as a video topic, you guys never disappoint. Absolutely love sci show.

[sd]

So what you're telling me is onions are trying to make me blind, by attacking my eyes with sulfuric acid?

[ZachlesTV]

Seeing new SciShow videos give me tears of joy!

[allhailskippy]

I'll be sure to mention that it's "just reflex tears" this June ;)

[rusted_ursa]

I love this show. I wish I was solvent enough for a monthly subscription. As it is, I will be giving one-time donations whenever I can until I am more financially stable.

[rickseiden]

I didn't cry while reading that certain teen book by that certain author you mentioned, but it was a great book, and I would highly recommend it.  I actually read it in essentially one sitting, which I never do.  That certain author did a great job, and I can't wait to see the certain movie that comes out soon.