Washington: How is it possible for a single entity to control or mould public opinion when others of its ilk also have access to the same information?

In the classic economic model of information manipulation, knowing more than anybody else is said to be the key to influence. Not true, says a new study.

The study, by University of Southern California economists Isabelle Brocas and Juan D. Carrillo, presents a situation where all parties have access to the same information, but one still manages to control public opinion.

"It's not necessary to have extra information," Brocas said. "You can induce people to do what you want just by stopping the flow of information or continuing it. That's enough."

The study, titled 'Influence Through Ignorance' and published in the latest issue of the The RAND Journal of Economics, illustrates the point with the example of pharma firm Merck.

For instance, the company may be obliged to make public the findings of all studies bearing on a new drug. Preliminary trials may indicate no short-term side effects. The company may choose not to conduct follow-up trials before releasing the drug for sale.

In Merck's case, a study released five years after the drug Vioxx was introduced showed that taking it significantly increased the risk of heart attacks. Merck funded the study, which had been intended to see if the painkiller was also effective against colon polyps.

Now, embroiled in a $4.85 billion settlement, the company claims that Vioxx poses no statistically significant long-term risk to the heart once it is no longer taken.

This claim is disputed. Merck stopped monitoring patients after only a year, discontinuing the study once the drug was taken off the market.

Similarly, the researchers explain, the head of a council may terminate discussion and introduction of new evidence about, say, whether to continue searching for weapons of mass destruction.

Calling for a vote when sentiment seems biased in a certain direction effectively curtails how much all members, including the chairperson, know about the issue at stake.

"Overall, the ability of to control the flow of news and remain publicly ignorant gives the leader some power, which is used to influence the actions of the follower," the researchers wrote.

Brocas and Carrillo are in the midst of a follow-up to the study that gauges how well individuals intuitively understand the "influence through ignorance phenomenon". IANS