When was the last time you had a good cry? Not a little tear or lump on your throat watching rescue puppy videos on YouTube, but a full-on wailing, tissues-flying tear session?
Sure, crying isn't often on people's to-do list of fun act activities, but a nice big cry can make us feel better (we will get to that later). Though, have you ever given thought to why, physiologically, salty water comes out of our eyes?
"There's a few different reasons why we cry," Doctor Eric Vanman, Senior Lecturer at the School of Psychology for the University of Queensland told The Huffington Post Australia.
Seeing tears coming from someone else's eyes that it tells you that it is a serious matter, and that they need some help.
"One of them would be that we do it because when we cry it sends messages to other people that we need support."
Think of it like emotional sign language. Sure, you might say you're okay, but your body is telling another story.
"You can think of it as a communicative function. Seeing tears coming from someone else's eyes that it tells you that it is a serious matter, and that they need some help. When you cry it signals to people that you're in some sort of disturbed state and need help," Dr Vanman said.
That physical reaction to an emotional feeling then triggers an emotional response in others.
"If a person sees another person cry, it makes them more empathetic. It seems to work more for men than it does for women, and that's perhaps because we see men cry less. If a man is seen crying it must be serious, that's what people tend to think. That's actually what we do in our lab, we've been studying, mainly, how people respond to other people's tears. If you don't show tears people will not necessarily realise or believe that you're sad or want to help you."
Aside from a cry for help (maybe that's where the term came from?!), it may also be due to an overwhelming amount of emotion.
"Another reason would be that you have so much internal stress or emotion built up, so it's an emotional release. That explains times when you're really sad, but also if you're angry, or if you're laughing at something so hysterically funny that it makes you cry. There's' so much internal arousal that tears become the release mechanism," Dr Vanman said.
When it comes to feeling sleepy afterwards, that is yet to be proven -- by science anyway.
"In regards to feeling sleepy after a big cry, people have looked into that. It's called the catharticism of it. Crying can have a cathartic effect in that it's a release and then you feel better. There isn't really much evidence for that, it's more anecdotal. Although, The one line of research that one of my PHD students is working on right now is looking at when you cry, perhaps it acts like a analgesic so that pain that you are about to face will actually be reduced. So the crying might have a short term analgesic effect," Dr Vanman said.
As for tears themselves, we actually have two types.
"Regarding actual tears, there's two functions for them. One is to keep our eyes clean of dirt and debris, and these tears are naturally produced to protect the eyeball, and are being constantly produced."
"Tears that come from crying, the type that fall down onto your cheek, they are different. They are coming from a slightly different tear duct. So biologically we have to have tears in our eyes to keep them clean, but the other tears from emotion are actually made of a different composition chemically, and that's being studied," Dr Vanman said.