A pet peeve of mine lately has occurred when I have read stories online or were talking to people. When people have written or spoken about agreeing or disagreeing with something or someone they have referenced the wrong body grammar or nonverbal cue. What I mean by this is that people have told me they have nodded their head no or have shaken their head yes. Yes, I am serious when I say this. The correct way of answering someone is to either:
Nod your head yes
Shake your head no.
Go on and try to do it the other way. Seriously try it. Try either one or do both:
Nod your head while saying no
Shake your head while saying yes.
Well did you try it?

I went around asking people to do this exercise and almost all of them said it was weird to nod your head while saying no and to shake your head while saying yes.
Yet people have been saying it aloud incorrectly or writing it down wrong.
This is a problem because it ruins the clarity in which you are trying to demonstrate to the reader.
Suddenly people don’t know if you agreed or disagreed towards what happened or what someone said.
This is similar to if you ever see a green stop sign.

Well, do you stop? Or do you keep going?
When I asked one of my friends this he said that he would just drift then. While this was clever, since to drift in a car you are both stopping and going at the same time, it doesn’t quite work that way in regards to grammar. You either understand the sentence or you don’t.
For those who still didn’t agree with this rule, I looked in the Oxford English Dictionary to further cement my point. According to Oxford, a nod is “an inclination of the head indicating acknowledgment, asset etc” (“nod”). It was also defined as “a quick voluntary inclination of the head, esp. one conveying salutation or recognition, expressing asset or approval, or directing attention to something” (“nod”).
The important part of those definitions, in terms of what I am addressing, is the use of the words acknowledgment, asset, and approval.
This shows that the word “nod” is to be used when agreeing with something or using nonverbal cues to say the word yes.
If done otherwise you have confused people in what you are trying to convey.
There are only two times it is okay to do the opposite.
If you are in another country that does the opposite.
If you are using the phrases rhetorically.
A majority of the world’s countries have accepted a nod to mean yes while shaking your head means no. However, there are some exceptions to the rule. These countries include:
Greece. Here tilting the head first to the left and then to the right means “Yes.” while tilting the head up and back means “No.”

Autumn at Accredited Language posted a blog on Tuesday, August 13, 2013, which explained how some countries use these phrases and nonverbal cues differently.
In Bulgaria and Albania, a head shake means “Yes” while nodding means “No.”
Residents of Saudi Arabia shake the head to say “Yes” and tip the head back to say “No.”
In Iran, dipping the head down indicates “Yes” while jerking the chin upward means “No.”
If you are in these countries the feel free to use those phrases in the opposite manner however if you are in the US, China, Canada, Mexico, and most parts of Western Europe, Africa, and the Middle East then don’t do it! The key here is knowing how to maintain clarity in the country you live in. Otherwise, if I ask you if you want extra jalapenos on your food and you nod your head at me while in the US and you meant no well sorry I take that as a yes.
The only other time is when writers are using the phrase rhetorically. Sadly most writers I have seen using the phrases are just using them incorrectly and not rhetorically. This method is tricky because you have to make sure your audience understands you are using it rhetorically. The only time I have seen this done right is when someone wrote that someone was nodding their head in a sarcastic manner. For example, if a mom was asking who broke the vase and then asked if Jerry did it, then the other child could say no while really nodding their head yes to fool the other sibling to thinking they were covering for them when really they were rating them out. This only works when the other sibling couldn’t see the other.
Overall you need to know how you are using phrases to maintain your clarity with your audience. 90% of the time use these phrases these ways:
Nod your head yes.

 Shake your head no.

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Used this blog as a source:

The Importance of Interpreting Body Language