Smart surfers are shying away from ads, and learning to distinguish between sponsored and non-sponsored links, according to new research funded by the US Air Force.

Jim Jansen, an assistant professor of information science and technology at Penn State University studied the rate of ad click-throughs on Dogpile.com, the meta-search engine that combines the search results from larger search engines such as Yahoo!, Google, Ask and MSN.

After examining more than seven million interactions from hundreds of thousands of users, Jansen found a click-through rate of only 15 per cent - around half that predicted by previous studies.

A third of web searches are fruitless

The findings also showed that for more than 35 per cent of queries, there were no clicks on any result.

"The result seems to show that web searchers are smart," Jansen said. "They have a good idea what web ads are and how to distinguish them from other links."

Although Jansen believes his study suggests that most consumers are distrustful of the ads, he also sees a benefit to advertisers.

"It opens the door to other forms of keyword advertising," Jansen said. "More research can be done on effective advertising, and search engine companies can improve ad mechanisms."

"There is a potential for growth if search users can overcome their trust issues," he continued. "It's just something that the search engine companies will have to work to overcome."