However, the study concludes that media sources have a significant impact on the number of questions that people were able to answer correctly. The largest effect is that of Fox News: all else being equal, someone who watched only Fox News would be expected to answer just 1.04 domestic questions correctly — a figure which is significantly worse than if they had reported watching no media at all. On the other hand, if they listened only to NPR, they would be expected to answer 1.51 questions correctly; viewers of Sunday morning talk shows fare similarly well. And people watching only The Daily Show with Jon Stewart could answer about 1.42 questions correctly.
“These differences may be small, but even small differences are important when we’re talking about millions of people,” said Cassino. “We expect that watching the news should help people learn, but the most popular of the national media sources – Fox, CNN, MSNBC – seem to be the least informative.”
Results for questions about international current events were similar. People who didn’t have any reported exposure to news sources were expected to answer 1.28 questions correctly, a figure which rose to 1.97 for people just listening to NPR, to 1.60 for people just watching The Daily Show or listening to talk radio, and 1.52 for people watching Sunday morning shows. By contrast, people who reported watching just Fox News were expected to answer just 1.08 questions correctly.