Do you recognize these two people? In both photographs, the eyebrows have been removed.
Here are the photos of the same faces. Is it easier to recognize them this way? This time the eyes have been digitally removed instead of the eyebrows. (Hint: one is a politician, and the other an actor)
Richard Nixon and Winona Ryder
Scientists have done facial recognition experiments where subjects were presented with many faces altered to have either the eyebrows or the eyes removed. It turns out that subjects perform better on faces with no eyes, compared to faces with no eyebrows.
As the authors put it, "The absence of eyebrows in familiar faces leads to a very large and significant disruption in recognition performance."
This came as a surprise to me, since I have always assumed that the eyes were the most important elements to help us recognize and remember a face, with the mouth being perhaps second most important.
Anselm van Hulle, 1649. Anna Margareta
It's remarkable that humans of both sexes have these patches of hair on our faces, compared to primates who generally have more facial hair. The muscles controlling their movement are sophisticated and largely unconscious. We express much about our emotional state to others, even at long distances away. This central role as a social signaler may be related to why eyebrows are also so important for recognition.
The authors of the paper note that:
"During the 18th century, in fact, in Western Europe full eyebrows were considered so essential to facial beauty that some upper-class women and courtiers would affix mouse hide to their foreheads. The perceived importance of the eyebrows for enhancing beauty has not waned to this day. Currently, it is relatively common cosmetic practice to use tweezers or depilatories to narrow and accentuate the arch of the eyebrows, as well as to remove any hair at the bridge of the nose. Cosmetics may also be used to alter the color (especially the darkness) and exaggerate the shape and length of the eyebrows."
A fundamental challenge in face recognition lies in determining which facial characteristics are important in the identification of faces. Several studies have indicated the significance of certain facial features in this regard, particularly internal ones such as the eyes and mouth. Surprisingly, however, one rather prominent facial feature has received little attention in this domain: the eyebrows. Past work has examined the role of eyebrows in emotional expression and nonverbal communication, as well as in facial aesthetics and sexual dimorphism. However, it has not been made clear whether the eyebrows play an important role in the identification of faces. Here, we report experimental results which suggest that for face recognition the eyebrows may be at least as influential as the eyes. Specifically, we find that the absence of eyebrows in familiar faces leads to a very large and significant disruption in recognition performance. In fact, a significantly greater decrement in face recognition is observed in the absence of eyebrows than in the absence of eyes. These results may have important implications for our understanding of the mechanisms of face recognition in humans as well as for the development of artificial face-recognition systems.