Newspaper publishers eager to have their results show up as more authoritative than others got a lesson in ranking results from Google (NSDQ: GOOG) Chairman and CEO Eric Schmidt, who told them Google News already does that. Asked at the Newspaper Association of America conference in San Diego today if there’s a way to tweak the algorithm to lean towards “credible brands,” Schmidt explained: “We actually do that in the case of Google News. Google News uses a relatively fixed set of sources which are selected based on exactly the kind of trust that you’re describing.”

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But general search is another matter: “We’ve been careful not to bias it using our own judgment of trust because we’re never sure if we get it right. So we use complicated ranking signals, as they’re called, to determine rank and relevance. And we change them periodically, which drives everybody crazy, as or algorithms get better. ... The usual problem is you’ve got somebody who really is very trustworthy, but they’re not as well-known and they compete against people who are better known, and they don’t—in their view—get high enough ranking. We have not come up with a way to algorithmically handle that in a coherent way.”

And even if Google does solve that, it won’t necessarily favor news organizations: “We don’t want to do the kind of thing you’re describing unless we can do it across the board and for all categories of trusted institutions, not just newspapers.