Doctor of audiology here. I think you are mistaken. The acoustic reflex cannot be triggered in this way. The reflex is triggered only after being exposed to a very loud sound.
Oh, Thanks. When I was a child I asked all the adults around about this, but they looked at me like I were a lunatic, so eventually I just stopped talking about it.... :) Glad to have an answer now.
I learned to do this as a child because I always had issues with feelings of pressure in my ears. I was so sensitive that riding up or down a hill that was big enough would cause discomfort.
I could imagine a visual form of it being a conditioned reflex. The stapedius reflex is also triggered by vocalization, so clearly some level of top-down modulation is possible.
I am loling, but I think perhaps parent meant to ask "how is it known [... to doctors of audiology]". I.e. how did people determine thay fact. Or maybe he was just being a smartass.
What is responsible for this?
I don't know how I discovered how to do this but it always seemed natural.