Photo: The Darwin Correspondence Project

There is no smile less convincing than the little kid picture smile -- the bared teeth, the expressionless eyes. And there is no smile sweeter than the fleeting ones that flicker across sleeping infant's faces -- though we're told those are just reflexes. What makes a facial expression expressive at all? How do we know what people's expressions actually mean? It was a question that interested Charles Darwin, and led to an experiment recently recreated by the Darwin Correspondence Project at Cambridge. Darwin took (pretty creepy) photographs of human faces with their muscles artificially contracted by electrical probes, and then asked friends of his to interpret the expressions.

You can click through the images and note what expression you think they express, and then view the results of the larger experiment here.  One result? People today have different words for emotions than Darwin's Victorian crowd did -- reminding us that what we think of as being innate emotions may well be social constructs. I know, it's deep. What strikes me most, though, is how uncanny, unsettling the photographs are, proving, if nothing else, the intangible qualities that go into these nonverbal human communications. In other words, a smile is not just some muscles contracting.

via It's Okay To Be Smart

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