Clarification: This version clarifies that not every article that mentions Robert Epstein’s research is missing from Google News. The missing articles relate to Epstein’s study on whether search engine results can influence elections.

Robert Epstein was searching for links to add to his Web site when he noticed something peculiar: Although articles about one of his research topics showed up in Google’s main Web search and in other search engines, Epstein could no longer find them on Google News.

That made Epstein, a psychologist who had recently written about whether search engine results can influence elections and who favors government regulation of online search, wonder whether Google was making his work on that topic more difficult to find. Epstein said he could still find articles related to his research on other topics.

The Washington Post has not confirmed those claims. Epstein, however, has collected evidence that he says supports his suspicion.

Epstein, a senior research psychologist at the American Institute for Behavioral Research and Technology, began exploring the effects of search engines on public opinion after a spat with Google, in which he accused the company of incorrectly identifying a Web site he ran as having malicious software. Google’s claim turned out to be true.

In recent months, Epstein’s research has caught the attention of publications including Time, the Nation and The Washington Post. But none of the articles on a study he released in March on how search engines could affect elections were showing up in Google News searches, Epstein said.

“Links that were on Google News to my voter ma­nipu­la­tion study appear to be gone,” Epstein said. “I looked on Bing and Yahoo, as well, but there was no change. This is a disturbing development.”

When asked about Epstein’s accusations, Google declined to comment. “Our focus at Google News is to surface the most relevant and up-to-date stories, yet we recognize that people also like to be able to dip into the archives directly from the News site. As part of our constant effort to improve the News experience for our users we are in the midst of upgrading our News archive,” the company said in a statement.

Searches for Epstein’s articles aren’t the only ones turning up next to nothing in Google News, a service that the company says sends 6 billion users to news sites across the Web every month. In Google News searches this week conducted by The Post, several articles on various topics dating as far back as April 2012 until last month didn’t show up.

These queries, when tried on Google News turned up no “news results” — similar to what Epstein encountered — and instead directed users to Google’s general Web search, where it can be difficult to sift news articles from other results.

Google’s focus on recent news could explain part of the issue. The Google News help page notes that the site’s main page only looks for articles that have appeared in the past 30 days and then directs users searching for older stories to Google’s archives. The biggest rush of articles on Epstein’s voter manipulation piece came in late March. Some more recent articles by Epstein, such as a piece last week in U.S. News & World Report, appear in the Google News search. Another May article, from the Nation, shows up if users look for the headline, but a problem on the Nation’s site directs searchers to an unrelated article.

Google’s time limit could also explain why Epstein could find several of the articles missing from his Google News search via rival search engines, such as Microsoft’s Bing. Stefan Weitz, Microsoft’s director of search, said Bing generally keeps articles in its news product for about a year.

Although the omission of Epstein’s articles about how Google could sway elections may simply be part of a broader problem with Google News, Epstein said he believes these incidents demonstrate the power search engines can have over public opinion.

“Google News is one of the largest news aggregators around the world,” Epstein said. “If you alter the news people see, you can alter the way they think.”

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