Spreading a message by word of mouth is all well and good. But how to find that first mouth?


Call it viral, buzz or word-of-mouth advertising: Getting customers to spread the word about a new product through their social or professional networks is a hot strategy in the marketing world. Its proponents insist that the technique--whether online or face to face--is sure to boost a company's return on investment.

But how can companies find the right individuals to deliver the message? Marketers may wonder if they are finding the best "seeding points"--that is, well-connected people at the hub of social networks who will latch on to a product and promote it widely among the people they know.

New research led by Wharton marketing professors Raghuram Iyengar and Christophe Van den Bulte, working with University of Southern California preventive medicine professor Thomas W. Valente, has found that traditional targets may not be as influential as previously thought. The pharmaceutical firm that sponsored the research for their recently published paper, "Opinion Leadership and Social Contagion in New Product Diffusion," had its "a-ha" moment when they found Physician No. 184 on a map.

The map was part of the researchers' presentation that reported the results to the sponsoring firm. Charted on the map was a tangle of points and lines representing physicians practicing in a large city and the connections between them. Researchers had tracked how prescriptions of a new drug spread from one physician to another, depending on who talked to whom and referred patients to whom.

Mapped out on the screen, the story became clear: The medical community was actually divided into two sub-networks split apparently by ethnicity, with one sub-network dominated by physicians with mostly Asian names and the other with mostly European names. Connecting the two, like a spider suspended on a thread between two webs, was the dot for Physician No. 184--a doctor the company's marketing department and salespeople barely knew.

Not only did the study indicate that word-of-mouth had been affecting physicians' prescription behavior--even after controlling for the effect of sales calls (referred to as "detailing visits" in the pharmaceutical industry)--but it also showed that converting the right individual could have a dramatic impact. And for executives in the conference room, it revealed something else: They had been overlooking some of the networks' most important social hubs.

"That was the biggest 'aha!' for the company," said Van den Bulte. Physician 184 "was not the most important in the number of connections he was getting, but he was vitally important in linking the networks."

Published in Forbes.