Classical manuals of rhetoric and medieval arts of poetry alike recommend speakers or reciters to support their words with appropriate behaviour of the body, and they distinguish in this connection between vultus and gestus. So, in his Poetria Nova, Geoffrey of Vinsauf writes:

Geoffrey here rates the expressive face and the gesturing body on a par with the speaking mouth in a reciter's performance: all three are equally linguae, tongues, instruments of communication. In the present chapter I turn from gestus to vultus.

As everyone knows, and as infants very early discover, there is more to be learned about what other people are thinking and feeling from their faces than from any other part of the body. The complex structure of facial muscles makes possible a very wide range of subtly varied expressions – some ten thousand, it is said – and the eyes play a special part also by the direction, duration, and intensity of a glance or a gaze. Not all facial activity, of course, entails any voluntas significandi. The primary purpose of the eyes is to receive information, not to convey it; yet they also serve to transmit ‘speaking looks’, actively intended by the gazer to communicate information to others.