Many of Dr. Pentland’s research studies with smartphones and badges with embedded sensors are discussed in his new book, “Honest Signals,” recently published by MIT Press. The badges use tools including infrared sensors to tell when people are facing one another, accelerometers to record gestures, and microphones and audio signal-processing to capture the tone of voice. With the array of sensors, the badges can detect what Dr. Pentland calls “honest signals, unconscious face-to-face signaling behavior” that suggest, for example, when people are active, energetic followers of what other people are saying, and when they are not. He argues that these underlying signals are often as important in communication as words and logic. - Meryn Stol