In Waltham, an algorithm developed by a startup company called Affectiva performed what is known as facial coding: it tracked the panelists’ raised eyebrows, furrowed brows, smirks, half-smirks, frowns, and smiles. (Watch a video of the technology in action below this story or here.) When this face data was later merged with real-world sales data, it turned out that the facial measurements could be used to predict with 75 percent accuracy whether sales of the advertised products would increase, decrease, or stay the same after the commercials aired. By comparison, surveys of panelists’ feelings about the ads could predict the products’ sales with 70 percent accuracy.