They eyebrow flash has been studied for decades most notably by German behavioural research scientist Eibl-Eibesfeldt. He found that the eyebrow flash is a universally recognized long distance social greeting. The only exception is in Japan where it is considered an overt sexual invitation and therefore inappropriate. For everyone else the eyebrow flash in a sort of nonverbal “Hello” or “Hey there, I know you”. The eyebrow flash happens very briefly and lasts only about one-sixth of a second. It is a quick raising and lowering of the eyebrows. The flash normally happens over a distance of between six to twelve feet by which dialogue can not easily occur, but of which, signals to another party that you have recognized them. The video of Fergie and Prince Andrew’s wedding provides a real life example of the eyebrow flash as she makes her way down the aisle.
The eyebrow flash could be a response to surprise, as if saying “Hey, I noticed you and am surprised, but also fearful because I’ve been taken off guard.” Therefore, the eyebrow flash sends the message that you aren’t a threat, since you’ve been taken by surprise. Another theory advanced says that the eyebrow flash draws attention to the face so that less ambiguous signals can be exchanged.
Research shows us that eyebrow flashes are infrequently used between individuals who are enduring strained relationships, so this can be used as a test. If you aren’t sure, try an eyebrow flashing on a colleague you’ve recently had a fight with. If the signal elicits a flash back then you have been forgiven, but if the flash is denied or you instead receive a dirty look then your transgressions are still at the forefront of their mind.
Eye contact between those in strained relationships is rigorously avoided under most circumstances, most likely so there is a reduced probability that the greeting extends to further unwanted interaction. We can therefore look at the eyebrow flash as a nonverbal conversation starter and lack thereof as a conversation avoider.