Media has always been partisan but when it was only partisan one way, that was the norm. It was considered objective and impartial. In the US, there were social conservative Democrats who believed in national defense and liberal Republicans who supported labor. Who can really remember whether Thomas Dewey or Harry Truman was a Democrat or a Republican? They weren't very different, really. The media were conservative.

Eventually that was going to change and it did. In the 1960s, media turned the other way and that was how it stayed until the late 1980s. Conservative commentary really only found a home on radio in 1992 and then it made it into television. Does that diversity lessen tolerance? A new paper argues it does, and says that viewing partisan news reports from both the conservative and liberal viewpoints makes people less accepting of their political opposites.

Countries that don't have partisan media have something worse - media that is all the same.

A survey of people in the United States and Israel asked how often they viewed liberal and conservative news outlets and how often they viewed mainstream, relatively neutral news sites. The results showed what surprises no one - that people who consumed a greater amount of partisan media content were more polarized, even if they viewed partisan content from both sides. Yes, NBC viewers will watch Fox just to know what to rant about, and vice-versa, except Fox viewers can watch anything else.

The U.S. data came from a survey of more than 600 citizens taken in the fall of 2012, before the presidential election. The Israeli data came from a survey of about 400 citizens just before and after the 2013 Israel national election.

"It means that getting your news from two partisan outlets on opposite sides of an issue is not the same as getting your news from one relatively neutral news outlet that tries to present both sides,"  believes R. Kelly Garrett, lead author of the international study and associate professor of communication at The Ohio State University, rather than seeing the obvious - that partisan people engage in confirmation bias. Partisan media does not create people.b"These results really underscore the importance of preserving a nonpartisan news media."

Preserving it? When did it ever exist? 

It isn't just the US, the survey findings were essentially replicated in Israel, where the political culture and the news media are very different. Politically, until the 1970s, America did not trust Israel because it was too socialist, it was only after repeated failures by the UN to keep the peace that America came around to being on their side.

In both countries, respondents were asked to describe their political leanings. There were then several measures designed to assess polarization. In the United States, for example, people were asked to rate how favorably they felt about political figures like Barack Obama and Mitt Romney.

In another measure of polarization, the Americans were asked how they would feel about having one of their children marry someone from the opposing political party, and whether they thought people from the opposing party were patriotic, intelligent, selfish and/or mean, among other traits.

The question for the researchers was: How much were these measures of polarization affected by the media that participants consumed?

American respondents were asked how often they went to online liberal news sites (such as Huffington Post and Daily Kos) or major news organizations that are frequently characterized as favoring liberal positions (such as the New York Times and MSNBC). They were also asked about their visits to conservative online news sites (such as Drudge Report or TownHall) or major news organizations frequently characterized as favoring conservative positions (Wall Street Journal and FOX News.)

Respondents also reported their use of mainstream sites that the authors deemed neutral, such as USA Today and CBS News.

The results showed that the more people visited partisan sites associated with their own views, the more polarized they were. In other words, they liked their own candidates more, and liked the opposing candidates less. They were even less likely to want their child to marry someone from the opposing political party, and were more likely to associate members of the opposing party with negative traits (such as being mean) and less likely to associate them with positive terms (like being honest).

"Heavy use of partisan media doesn't just affect your attitudes about the other party's candidates," Garrett said, "It also affects how you think about the other party's supporters – you'll be more likely to see them as less patriotic and more close-minded, for example."

People who visit partisan sites associated with the opposing party are less polarized – they don't have such negative attitudes about the candidates and supporters of the other political party. That's why they don't visit such partisan sites.

Garrett and colleagues still insist they have found a troubling interaction effect: That polarization is actually amplified when people view a lot of partisan content associated with their own political views and also a lot of content associated with the opposition. There was some evidence of that in the United States, but even stronger evidence in Israel, where the researchers could see how use of partisan media on both political sides at one point in time was linked to further polarization later on.

Garrett said he thinks he knows why.

"We know that partisan media will ridicule people on the other side, and may even encourage their supporters to go to the opposition websites to see the horrible things they are saying," he said. "So people aren't consuming media on both sides of the issue to understand what the truth is. They're seeking out the other side just to see how wrong-headed they are."

Garrett said that a nonpartisan, neutral media still has its place in society.

"Our results in the United States underscore the importance of preserving a nonpartisan news media," he said. "The mainstream media have a value beyond the business itself and could help limit some of the partisanship we have seen in this country."

We all look forward to that idealized future. It certainly never existed in the past.