Have you noticed that people can tell when you are staring at them even in a car? How they turn and stare back? A double take has the effect of staring, but is 100 percent better. In effect, you are saying that something (another person, object, or activity) caught your attention. Since humans are by nature curious, this person will want to know what you see. He or she will meet your gaze, and–Eureka!–from across a crowded room something will have begun.