It's not exactly behavioral targeting, but Google is betting that its new experiment may just give advertisers the same -- or better -- results.

Google's AdSense program has always keyed off of the text on a page, which in turn has some probable relationship with the user's initial query. But now the search giant is tinkering with ways to serve ads based on terms people use in a given online session.

"We are trying to understand what the user is trying to do right now," Nick Fox, Google's director of product management, told The New York Times. "In some cases, those queries are ambiguous, so you need a little more context. It is probably not just the previous query that matters. You want to know if the user is still doing the same thing. You wouldn't want to go back a month. You wouldn't want to go back a day. But you may want to go back two or three queries."

If successful, the new Google experiment should be able to discern the intent of a user's entire search session. For example, if a user was planning a vacation, his searches might include locations, airfares, hotels and activities. While BT aims to get at the same information by scrutinizing sites visited and actions taken on those sites, Google is betting that users are likely to telegraph their plans, whatever they may be, based on what they search for in a session that could last a few hours or more. Picking up on the above example, Google may be able to immediately serve an ad for a ski lodge in Colorado that emphasizes an accommodation and lift ticket package.  

To be fair, Google's competitors are trying to offer the same insights to advertisers. But Yahoo, AOL and Microsoft, all of which have spent hundreds of millions to acquire BT companies, don't have the search data that Google has at its disposal. That fact gives Google a somewhat unique position in the space insofar as its competitors likely wouldn't have enough historical search data to extrapolate meaning from the myriad of terms a person uses in a given session. But as good as Google's search data is, it could get even better if it's able to team with Yahoo to monetize that company's search results. That deal will likely need regulatory approval before Google can proceed.