“Your heart-rate signal is in your face,” said Ming-zher Poh, an M.I.T. graduate student. Other vital signs, including breathing rate, blood-oxygen level and blood pressure, should leave similar color and movement clues.

The pulse-measuring project, described in research published in May by Mr. Poh, Mr. McDuff and Rosalind W. Picard, a professor at the lab, is just the beginning, Mr. Poh said. Computer vision and clever software, he said, make it possible to monitor humans’ vital signs at a digital glance. Daily measurements can be analyzed to reveal that, for example, a person’s risk of heart trouble is rising. “This can happen, and in the future it will be in mirrors,” he said.

Faces can yield all sorts of information to watchful computers, and the M.I.T. students’ adviser, Dr. Picard, is a pioneer in the field, especially in the use of computing to measure and communicate emotions. For years, she and a research scientist at the university, Rana el-Kaliouby, have applied facial-expression analysis software to help young people with autism better recognize the emotional signals from others that they have such a hard time understanding.

The two women are the co-founders of Affectiva, a company in Waltham, Mass., that is beginning to market its facial-expression analysis software to manufacturers of consumer products, retailers, marketers and movie studios. Its mission is to mine consumers’ emotional responses to improve the designs and marketing campaigns of products.

John Ross, chief executive of Shopper Sciences, a marketing research company that is part of the Interpublic Group, said Affectiva’s technology promises to give marketers an impartial reading of the sequence of emotions that leads to a purchase, in a way that focus groups and customer surveys cannot. “You can see and analyze how people are reacting in real time, not what they are saying later, when they are often trying to be polite,” he said. The technology, he added, is more scientific and less costly than having humans look at store surveillance videos, which some retailers do.

The facial-analysis software, Mr. Ross said, could be used in store kiosks or with Webcams. Shopper Sciences, he said, is testing Affectiva’s software with a major retailer and an online dating service, neither of which he would name. The dating service, he said, was analyzing users’ expressions in search of “trigger words” in personal profiles that people found appealing or off-putting.

Watching the Watchers

Maria Sonin, 33, an office worker in Waltham, Mass., sat in front of a notebook computer looking at a movie trailer while Affectiva’s software, through the PC’s Webcam, calibrated her reaction. The trailer was for “Little Fockers,” starring Robert De Niro and Ben Stiller, which opened just before Christmas. The software measured her reactions by tracking movements on a couple of dozen points on her face  mostly along the eyes, eyebrows, nose and the perimeter of her lips.