We should do a test on the whole site to see if there's anything relating to the main hand and what eyebrows they can raise. Who's ready for a science experiment?
For all it' s worth a quick google search tells me that it' s not genetic, that it can be trained, and that most people can raise both but have trouble raising a single one. I can raise any of them or both, but the one I' ll naturally raise to express incomprehension is the left one (I' m right handed). That' s what made me an open book to my teachers.
