Marketers know there's a lot more to measuring the success of an ad campaign than the clickthrough rate (CTR), but how do they narrow down the most meaningful metrics? eMarketer’s Bill Fisher spoke with Mike Pallad, president of Undertone, and Laura Salant, the digital advertising company's senior director of research and insights, about the importance of "attention"—and how measures of attention are evolving to provide insight into the effectiveness of ad creative.