I can raise either, roll tongue to shoot spit-wads, use as straw, etc, cross my eyes, cross one eye, move one eye in circles while the other is crossed, etc, but I’ll be damned if I can describe how to do it. Best I can say is stand in front of a mirror and practice. Use the force maybe, or, email Chuck Norris. I hear he doesn’t actually raise one eyebrow though, he just uses the other one to push the whole planet down.