Thank you for your question! I was quite surprised to discover that
learning to raise one eyebrow independent of the other is a popular
pursuit. 38 people list "learn to raise an eyebrow" as a personal goal
on the highly addictive website "43 Things"
(http://www.43things.com/things/view/37844). The page devoted to this
particular topic features tips and comments from users who have
mastered the technique. Here's a sampling of what they suggest:
"I litterally [sic] taught myself how to do it by holding one down and
raising them until I could get the feel of it."
"You start by frowning and pulling both brows down, then try to push
one up. Practice using your fingers to help it up first and then you
will eventually get the hang of it and be able to do it yourself."
For a more scientific approach, you may wish to consult the DataFace
website. DataFace is concerned with the study of the human face,
facial expression/emotion and nonverbal communication. You'll find
step-by-step instructions for performing the single-eyebrow raise
under section B at <http://face-and-emotion.com/dataface/facs/manual/AU2.html>.
While technical jargon abounds, you'll get the gist of how to cement
the look from instructions like the following:
"Using your fingers push up the outer corners of your eyebrow to see
how it changes the appearance of your face. Try to hold the appearance
when you take your fingers away."
You may also be interested to learn that according to most of the
sources I consulted, the ability to do this particular trick with ease
seems to be largely genetic; with practice, however, you may be
pleasantly surprised to find yourself, or at the very least an
eyebrow, rising to the occasion.
The following search strings were helpful in finding your answer:
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Now -- go and show those eyebrows who's boss!