Crying is often cathartic. It's an emotional release triggered by a range of feelings — sadness, love, anger, and grief, to name a few. So when you're watching a scene from a television show or movie that makes you feel things, it's a totally normal response. So normal, in fact, that there's an entire MTV Movie & TV Awards category dedicated to things that make us cry.

But not all cries are created equal.

Why is it that when MTV Best Actor nominee Mandy Moore sheds a tear on This Is Us, audiences feel empathy, while Kim Kardashian's tears are meme-ified for the internet's entertainment? Even Claire Danes and her Emmy-winning cry faces have been the butt of internet jokes.

It's not that Danes is exaggerating her sobs for the camera; in fact, it's more likely that she is just extremely good at her job, specifically the crying part of it.

"She gets that sad face, and it kind of lingers and then it fades out, but it's very slow," body-language expert and speaker Patti Wood told MTV News. "That's one of the reasons we're affected by it so profoundly, because most of the time real crying doesn't disappear. True crying lingers and comes and goes in waves."

When we see someone cry onscreen, the mirror neurons in our brains fire, which elicits a very primal response from us — one that mimics what we're seeing. Isopraxism, or the pull to the same energy, is also in effect. "Isopraxism in nature explains why birds fly together and deer run together and why people applaud," Wood said. "That's another thing that's part of what's going on when people see and hear people crying on the screen."

Of course seeing someone cry doesn't always elicit the same response. As Dr. Meredith Grey on Grey's Anatomy, Tearjerker nominee Ellen Pompeo is one of television's most seasoned criers — and also one of the most effective. According to Ad Vingerhoets, the world's foremost expert on crying, how the person cries is an important determinant of how audiences will respond to a character's tears.

Wood says: "In sadness, the inner corners of the eyebrows go up, the eyelids droop, the corners of your mouth go down, and sometimes there's this weird change in the cheeks, like the cheek muscles go toward the nose. In agony, you're pulling your facial muscles in a lot toward the center and downward. That combination is exactly the opposite of what you might find attractive.

"Typically, the facial muscles are balanced and … lifted up, so the eyebrows go up all the way and the eyelids don't droop, they stand up straight; the corners of the mouth go up and the cheeks go up, so you get this upward balanced expression," she added. "In crying, specifically in agony, you get this mixture of up and down, but a lot of down."

To audiences, that downward movement might not be the most aesthetically pleasing. "To us, it might look ugly, and ugly is unpleasant," Wood said.

And when viewers feel unpleasant or uncomfortable, laughing is often a go-to stress response. "We're fighting against the emotion — in this case, sadness — to laugh," she explained.

The relationship the audience has with the crier is also important. For a public persona like Kardashian, some people might feel apathetic toward her emotions, and for an actress like Danes, it might be that her portrayal of pure, unfiltered agony is just too real for some audiences to feel any empathy. Hence her heavily memed facial contortions.

Be sure to tune in to the 2017 MTV Movie & TV Awards on Sunday, May 7, at 8 p.m. ET/PT. And check MTV News for all your updates on the big show.