Since I was 10 I have been working to control what are normally involuntary responses or muscles, and I was able to teach myself to wiggle my ears, control my heartbeat to a large extent, pop my ears (or repressurize them even!) at will, but I could never quite control hiccups until I found this page, so thank you!
I knew this must be another controllable action since one of my friends has been able to do this for a few years, so when I was hiccuping one day I checked the web to see if others with the ability had managed to explain a method for achieving this, and I stumbled across this page, followed the instructions, and now I’m glad to say I can add it to my list! Thank you!!
And I share his ability to open my eustachian tubes on command to pop my ears!