With a group of more than 1,800 study participants – all undecided voters in India — the research team was able to shift votes by an average of 12.5 percent to favored candidates by deliberating altering their rankings in search results, Epstein said. There were also increases in the likelihood of voting and in measurements of trust for the preferred candidates, and there were decreases in the willingness to support rivals. Fewer than 1 of every 100 participants, meanwhile, detected the manipulation in the results.

“It confirms that in a real election, you can really shift voter preferences really dramatically,” said Epstein, now a senior research psychologist for the American Institute for Behavioral Research and Technology, a non-profit group based in California, which conducted the study.

Skeptics of Epstein’s previous work, which was presented at last year’s meeting of the Association of Psychological Science, noted that voters typically have a range of information sources beyond what search engines provide and are swayed by other factors, such as party allegiances, potent issues and ethnic and religious affiliations.