By Steven Johnson

This interview with Paul Ekman, the UCSF psychologist who has become something of a celebrity in the past few years, is a good place to start answering the question I posed in the previous entry: how does knowing something about the mind's inner workings change the way we think about ourselves as individuals?

Ekman is famous for proving the universality of the basic language of human facial expressions (a premise notoriously rejected by Margaret Mead many years ago). But he's also brought to light the subtleties of our expression-reading skills, our knack for detecting the micro-expressions that go beyond the basic palette of seven primary emotions. These skills are part of what some neuroscientists refer to as our "mindreading" system: the part of our brain that's constantly trying to guess what other people are thinking, using all the potential clues available to us, many of which take the form of subtle changes in the musculature of the face.

Mindreading is one of those topics where the "hominid" approach and the more personal, introspective approach nicely overlap. We're all innately talented mindreaders -- unless we're autistic, or suffer from some other comparable disorder. We don't go to school to learn to read facial expressions, even though they utilize an amazingly sophisticated symbolic system. But some of us are better mindreaders than others -- we're better at reading those split-second changes in facial expression or vocal intonation, and thus better at assessing the true meaning of another person's inner thoughts and feelings.

The more you learn about the science of mindreading, the more you find yourself dividing up your friends into two camps: the mindreaders and the mind-dyslexic. It's not a psychological filter that you carried around consciously before, the way you might have thought of certain friends as being extroverts, and others being repressed. But once you apply the filter, it has a revealing quality: you find yourself saying -- "That's why I always had such great conversations with her!" Or: "No wonder his jokes always fell flat."