How can I defuse a violent argument between two people?

Question

TL;DR

How can I calm the situation when my mother and sister are violently arguing without the situation backfiring at me?

Background

The other day, my mother and my little sister (17 years) were arguing (my sister didn't wanted to do what my mother wanted her to do because of X) and the situation was getting a little out of hand. In fact, I was worried things were going to degenerate.

This isn't the first time this kind of violent arguing has happened and I never know what to do to make everyone calm down. Most of the time, I just change place in the room and just stand, looking at them, hoping they will notice me (I guess I'm trying to silently say "I'm here, I'm watching you, be careful with your words and, please, stop arguing").

Example of the last time my mother and sister were in an argument:

My sister was watching a TV show on her computer. My mother wanted my sister to accompany her at X so that my sister would do some sport (instead of staying at home all day). My sister didn't wanted to. My mother got really mad (overreacting like she was having a mood swing) and tried to take the computer from my sister's hands by force. In the meantime, my mother was saying in an angry voice:

You spend to much time in your computer, you are going to come with me!

Question

How can I use to defuse the situation without them getting mad at me for saying something?

I just want them to stop arguing so violently and start talking/negotiating like civilized people.

Answer 1

This can actually be very difficult.

First timing is an issue, and are you going to intervene?.

Arguing can actually be fairly healthy between two people. It allows them to show emotions and feelings without festering them. But as you said you don't want it to get physical. So screaming and yelling might not be a good time to intervene, but when your mom and sister are getting physical it might.

Try to see when they start to get in each others space, look at body language.

Your comment is a very good one!

Choosing sides

Ask yourself, Am i choosing sides? Or how would it appear to them? You are spot on that you don't want to choose a side. But comments like:

My mother got really mad (overreacting like she was having a mood swing)

Can make it appear to your mom you are, so try to stand in their shoes and how you appear to them when you intervene.

So try to intervene without appearing to choose sides, don't get into the middle of the argument, but in the middle of them.

Try interjecting by commenting their behavior and make sure you direct it to both.

When you step in, try to remain neutral and focus on diffusing the physicality of the argument.

Example

I would be honest and most importantly in a calm/relaxing way tell them what you said:

"I really don't like it when you are both fighting/shouting/hurting each other, I love you both. Could you guys please sit/eat ice cream/take a walk and talk it out?"

Don't put emphasis on civility or the argument it self. Then it won't be seen as meddling or choosing sides. But again it might depend on the situation. Make sure you aren't intervening just an emotionally healthy argument, try to assess the situation.

My answer is based on anecdotal experience.

My experience is not directly related to the specific sister-mother situation. But when parents fighting or my ex and her mother it did work. Also as my job I sometimes mediate between heated discussions in which also I try to not choose sides but appeal to getting a result in a healthy manner.

I actually mentioned some of my own experience while being part of an emotional argument see: https://interpersonal.stackexchange.com/a/4924/6719