What he does, he explains, is track the ups and downs of a couple’s level of positive and negative emotion, and he’s found that it doesn’t take very long to figure out which way the line on the graph is going. “Some go up, some go down,” he says. “But once they start going down, toward negative emotion, ninety-four percent will continue going down. They start on a bad course and they can’t correct it. I don’t think of this as just a slice in time. It’s an indication of how they view their whole relationship.”