You are more likely to think other people are attractive if they are looking straight at you and smiling. According to new research, humans find smiling members of the opposite sex more attractive when that smile is coupled with eye contact than when the gaze is averted. The combination is attractive, researchers report online 6 November in the Proceedings of the Royal Society B: Biological Sciences, because a person looking directly at you and smiling might be more likely to respond positively to advances than a person who is disgusted or happy to see someone else.

Claire Conway and colleagues at the University of Aberdeen in Scotland, UK, paired nearly identical photos of computer-generated faces, with smiling or disgusted expressions. The pair differed only in where the irises were pointed: straight at the viewer, or off to the side (see image).

Several hundred Aberdeen undergraduates, in the lab and online, rated the faces for sexual attractiveness, and for likeability, a sexually neutral quality. Both men and women found faces looking straight at them to be more attractive and more likeable, even if the faces looked disgusted though unsurprisingly, there was a greater preference for smiles.

But when the viewers were rating the faces for attractiveness, the preference for being gazed at directly by smiling eyes was much greater for faces of the opposite sex, especially when they were rated by men. There was no such sexual bias in the preference for a direct gaze when the students rated disgusted-looking faces, or when they were rating any faces for likeability.