There is a common English phrase "It takes one to know one."
Basically it means that sometimes you need to experience or be something to recognize another person who has experienced the same thing.
My Dad is a signing grandpa and in a recent channel surf he recognized something in a TV interview that most people probably missed.
Mariah Carey was on TV last week and while talking about her twins she shared about her daughter relaying a time when her daughter asked if a room in the house was her's. Mariah made gestures for "my" and "more" that looked like 2 yr old signs so my Dad asked if I knew if she was signing with her kids.
Honestly, I have no idea if Mariah Carey does some kind of Baby Sign Language.
What I do know is that when I relay something my kids have told me I often mimic their signs and words.
I also know that the hand gestures she made mean nothing to most people but if you are around a signing 2 yr. old you may see them as signs!
You can see the whole video of her interview for yourself. The "Signing Moment" I'm talking about happens about the 1:50 mark so you can skip to that area if you prefer.