" ... this is why Gottman has couples talk about something involving their marriage — like their pets — without being about their marriage. He looks closely at indirect measures of how the couple is doing: the telling traces of emotion that flit across one person's face; the hint of stress picked up in the sweat glands of the palm; a sudden surge in heart rate; a subtle tone that creeps into an exchange. "

― Malcolm Gladwell , Blink: The Power of Thinking Without Thinking