Faces call the trust code in our brains

Brad and Dave have been writing about the power of faces in user experience, but are missing the reason they are so powerful. As I said in The Social Cloud, and stressed again last week at Ignite I/O, Douglas Adams got this right 10 years ago:

Of course you can’t ‘trust’ what people tell you on the web anymore than you can ‘trust’ what people tell you on megaphones, postcards or in restaurants. Working out the social politics of who you can trust and why is, quite literally, what a very large part of our brain has evolved to do.

Trying to model these trust relationships in the computer is fraught with hubris and failure, but what we can do is associate information with people, and display the information from people we know, with their pictures (and names) next to it. Then, our brains can apply the subtle modelling of trust relationships that they have evolved to do so well.
Making faces bigger onscreen lets us blend the two modes of computation smoothly, and filter and understand the world better through our nuanced understanding of trust.