The role of eyebrows in face recognition
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 45 Carleton Street, E25-201, Cambridge, MA 02142, USA; e-mail: firstname.lastname@example.org; email@example.com Received 23 April 2002, in revised form 4 November 2002; published online 7 March 2003
Javid Sadrô, Izzat Jarudi, Pawan Sinhaô
Abstract. 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.
1 Introduction Evolutionary history has seen a considerable reduction in the amount of hair on the human face (McNeill 2000; figure 1). As such, the presence of the eyebrow might seem a curiosity. Do the eyebrows in fact serve a useful purpose or are they merely an evolutionary vestige? While it is perhaps true that eyebrows may provide the eyes modest protection against such things as rain and perspiration, it is perhaps more relevant that the eyebrows also appear to serve a number of functions that are more visual in nature. Eyebrows may serve as high-contrast lines that give the appearance of the brow greater clarity and emphasis, and their associated musculature allows for sophisticated, often involuntary gestures that may be discerned from a relatively large distance. As such, the eyebrows appear to play an important role in the expression of emotions and in the production of other social signals, and they may also contribute to the sexual dimorphism
Figure 1. Overall, humans have relatively little facial hair as compared to other primates; the conspicuous presence of the hair forming the eyebrows is somewhat intriguing. A number of selection pressures may be responsible for the development and persistence of the eyebrows over the course of primate and especially human evolution. A color version of this figure can be seen at http://www.perceptionweb.com/misc/p5027/. ôAuthors to whom correspondence and requests for materials should be addressed.
J Sadr, I Jarudi, P Sinha
(ie sexual differentiation) and even the aesthetics of faces. Here, we begin by reviewing past work concerned with the appearance and functions of the eyebrows, then proceed to empirically investigate whether the eyebrows also play an important role in the recognition of faces. Practitioners in the field of facial aesthetics, such as make-up artists and cosmetic surgeons, have long appreciated the influence of eyebrows on attractiveness (eg Cosio and Robins 2000). 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...