Why do some people, sometimes, "cry" when they are laughing?

I believe scientists still don’t know how we cry, but I can give you an example as to what causes the event.

When you tickle someone who’s ticklish, they laugh not just because they are happy, but because the nerves react to the touch differently than, say, a pinch or a punch. The information sent to the brain is interpreted as “This is a touch that is not harmful nor usual,” and that unusual feeling can cause the output of a laugh or giggle or a riotous drunk-man collapse of joy.

The reason some people cry is that their brains believe the touch is starting to become more threatening or imminently dangerous. This can happen if a person is being tickled too much, or if someone is extremely sensitive to a tickle. That threat of pain goes through that unexplainable process and the person begins to tear up.

Be warned, though, that this is my best guess and is not proven by any written or otherwise exterior source. Of course, it should be somewhat correct, as I am extremely ticklish.

@Rachienz: I don’t think I know anyone that hasn’t teared up because of a giant belly laugh. So the comment that it doesn’t happen to all people struck me as odd, maybe not all the time, but I’m sure it happens.

Laughing and crying aren’t that different. Your body moves the same way while laughing as it does when sobbing. I’d be surprised if a lot of people didn’t tear up.

As to why, I have no idea.

Just speaking personally here, I think being tickled is a kind of pain much as itching is a kind of pain, and the reaction is not joy or happiness at all. The reaction is involuntary, and it tends to look like fun, but I do not think it is fun. I think tickling kids until they’re helpless with laughter is just plain cruel.

As for laughing until you cry, there’s the physiological part and there is also the emotional part. Emotionally it is a very intense experience to laugh that hard, and some people react to intense experiences with tears, as we see during every Olympics.

When I laugh until I cry, I am not really crying at all—it is not physically or emotionally like crying—but it is a kind of physical and emotional stress, and the systems that process both responses are very closely related, or so it seems to me, so one can spill over into the other.

When I really get onto a laughing jag, as I occasionally do, it ends up hurting and I want it to stop. Like being tickled, it can be an experience that feels a lot like pain.

Hence the term “dying laughing”. It DOES hurt, and it usually happens during what is often called uncontrollable laughter. What happens when we find ourselves in a situation that is beyond our control? We get scared, and or cry. Whether subconsciously or not, this seems to be the case with laughing.

But I do plan to die laughing. That is literally my ultimate goal in life.

I’m disagreeing with a lot of these answers. When I laugh so hard that tears stream down my face, there isn’t a single part of it that’s negative. Yes, it can get a little annoying if my stomach starts to hurt, but that certainly isn’t what’s causing me to cry especially since I’ve laughed until I cried before plenty of times without my stomach hurting. I don’t know the answer to the question, but at least in my case, some of the answers given don’t work. Crying is often a response to strong emotions like sadness, but it also can happen when there’s extreme levels of happiness, sentimentality, or laughter. Crying/tears isn’t just about pain. I’ve known epic classical music to make me cry. What of that?

My thought has always been that tears are a response to any strong emotion. We cry when sad, scared, happy, touched, nostalgic, etc.

As for tickling, which I know is a little off-topic, I agree that it is not funny to tickle children until they are begging you to stop. I do think think being tickled is fun, though. There is a reason kids are always saying, “tickle me again!!” You just have to know when to stop.

Laughing until you cry is one of the most beautiful things in life and every time we do it we should think how lucky we are to be that happy!!!!!! I love it.

Crying is a fascinating thing though. When you’re sad, it seems the tears just never end. Interesting how they just keep on being produced!

My eyes pop out tears even when I am talking about things that make me happy. Maybe my tear ducts are closer to the surface than other people.

Endorphins, same reason people laugh when they should cry.

I agree with @Supacase in that crying seems to have some sort of correlation with emotion. I cry when I see or hear something beautiful. I’ve laughed til I cried many times. I have also cried when I was happy or thankful. I think crying goes far beyond just sadness and pain. It’s a beautiful (and sometimes perplexing) thing.

The last months, i don’t know why, i cry for ‘nothing’.
Well, shed a tear for ‘nothing’.
For example: @Supacase saying; “kids are always saying, “tickle me again!!””
I read it and directly i ‘see’ ‘my’ kid saying that and there i go.
Such sweet image.

I just thought of a possible reason why we cry…when we are infants, crying is our sole means of communication. Perhaps this “instinctual” communication method is carried with us our whole lives and used, by default, when our minds are unable (or possibly slow) to process our emotions into words. Maybe in times of duress our mind “panics” and reacts in the easiest way it knows how by crying. Many instances when I’ve cried have been related to events that were so overwhelming, it took me a few moments to “find the words”. Whatever the reason, I’m glad we can…in most circumstances it is VERY pacifying; nothing makes me feel lighter inside than a good, hard cry.

I would agree with a lot of what all of you are saying BUT I sometimes laugh so much that it is no longer laughing with tears, it is actually hysterical crying. I am such an emotional person that so much emotion has built up to a point where I can’t contain it anymore and the only reaction left is to cry. It starts out as a happy feeling but unless I gain control quickly I become depressed and unbelieveable sad. I have no reason for being sad but I can’t help it. I then have to remind myself that nothing bad or sad has happened and why I started laughing in the first place. This is a very different experience to the ones everyone has mentioned above. I don’t think there is anything wrong with me as I am just a very emotional person and find controlling that emotion very difficult.

I have overactive tear ducts. My tears pop out all the time.