In the everyday business of interpersonal interaction, faces do a lot of the important work. As well as carrying their own specific meanings, they set the tone for whatever else is happening, ironizing the surface content of a sentence or drawing attention to hidden semantic subtleties. A criticism delivered with a smile or wink, for example, has a quite different effect from one accompanied by scowls. Being face-to-face also makes obvious and inescapable differences to how we engage with one another. Catching someone's eye is often a prerequisite to starting a conversation, and the course of the ensuing dialogue is directed and redirected by the exchange of looks, yawns, and grimaces. As we interact, we seem to be acutely responsive to the slightest twitch or contraction of facial muscle.
Why do people devote so much attention to faces? The obvious answer is that important information can be derived from them. But that is only part of the story. Our looking also conveys our engagement. The act of collecting information provides information collected by the other person in a corresponding act. We see each other collecting information and coordinate our perspectives (or arrive at opposing positions, or break away from the interaction). More generally, facial movements (including looking) not only serve to provide information for someone else to decode, but also play a more direct role in the performance of interpersonal action.
This chapter reviews psychological thinking about faces as sources of information and as vehicles for action. We try to broaden the usual