From Darwin’s famous early dabbles in the science of facial expressions to Duchenne’s legacy, from evidence of babies practicing smiling in the womb to studies suggesting a positive correlation between smiling and longevity, LaFrance blends a researcher’s rigor with a social scientist’s humanism in an intelligent yet highly readable narrative, complete with 38 illuminating black-and-white illustrations. LaFrance writes:

Smiles are universally recognized and understood for what they show and convey, yet not necessarily for what they do. Smiles are much more than cheerful expressions. They are social acts with consequences.

Wired has an excellent interview with La France, for a taste of the book’s fascination:

People think they can tell by looking at what the overall face looks like, but in fact there is one muscle [that shows sincerity]. It’s a muscle, called the obicularis occuli, that encircles the eye socket. Most people don’t pay very close attention to and it’s very hard to deliberately adopt. So when people genuinely smile, in a true burst of positive emotion, not only to the corners of the mouth, controlled by the zygomaticus major, but this muscle around the eye also contracts. This causes the crows feet wrinkles that fan out from the outer corners of the eyes and its also responsible for folds in the upper eyelid. Most people can’t do that deliberately.

Lip Service is part Liespotting, part The Exultant Ark, part whole new way of looking at our most powerful nonverbal expression of shared humanity.

Thanks to Flickr Commons for the endless bounty of public domain images