Feinberg DR. Are human faces and voices ornaments signaling common underlying cues to mate value? Evolutionary Anthropology. 17:112-118.

In our daily lives we constantly interact with people. We maintain relationships with families and friends. We collaborate with colleagues. We seek passion with our lovers, and avoid conflicts with our enemies. How we divide the world into these and many other categories of people is initially guided by our first impressions of how they look and sound. Many times we are surprised when we hear someone that we have not yet met face-to face on the phone; they look different than what we imagined. There are, however, many things that we are not surprised about in the above situation. People are accurate at identifying sex, health, emotions, and age by voices and faces. There is good evidence that other seemingly disparate ornaments such as body and face, body and voice, and face and odour may convey either backup signals of the same underlying quality, or convey signals of different underlying qualities that are used in conjunction to provide a more robust view of the organism