How the Internet Is Loosening Our Grip on the Truth

Much of that remains unclear, because the internet is distorting our collective grasp on the truth. Polls show that many of us have burrowed into our own echo chambers of information. In a recent Pew Research Center survey, 81 percent of respondents said that partisans not only differed about policies, but also about "basic facts."

For years, technologists and other utopians have argued that online news would be a boon to democracy. That has not been the case.

More than a decade ago, as a young reporter covering the intersection of technology and politics, I noticed the opposite. The internet was filled with9/11 truthers, and partisans who believed against all evidence that George W. Bush stole the 2004 election from John Kerry, or that Barack Obama was a foreign-born Muslim. (He was born in Hawaii and is a practicing Christian.)

Of course, America has long been entranced by conspiracy theories. But the online hoaxes and fringe theories appeared more virulent than their offline predecessors. They were also more numerous and more persistent. During Mr. Obama's 2008 presidential campaign, every attempt to debunk thebirther rumor seemed to raise its prevalence online.

In a 2008 book, I argued that the internet would usher in a "post-fact" age. Eight years later, in the death throes of an election that features a candidate who once led the campaign to lie about President Obama's birth, there is more reason to despair about truth in the online age.

Why? Because if you study the dynamics of how information moves online today, pretty much everything conspires against truth.

The root of the problem with online news is something that initially sounds great: We have a lot more media to choose from.

In the last 20 years, the internet has overrun your morning paper and evening newscast with a smorgasbord of information sources, from well-funded online magazines to muckraking fact-checkers to the three guys in your country club whose Facebook group claims proof that Hillary Clinton and Donald J. Trump are really the same person.

A wider variety of news sources was supposed to be the bulwark of a rational age — "the marketplace of ideas," the boosters called it.

But that's not how any of this works. Psychologists and other social scientists have repeatedly shown that when confronted with diverse information choices, people rarely act like rational, civic-minded automatons. Instead, we are roiled by preconceptions and biases, and we usually do what feels easiest — we gorge on information that confirms our ideas, and we shun what does not.

This dynamic becomes especially problematic in a news landscape of near-infinite choice. Whether navigating Facebook, Google or The New York Times's smartphone app, you are given ultimate control — if you see something you don't like, you can easily tap away to something more pleasing. Then we all share what we found with our like-minded social networks, creating closed-off, shoulder-patting circles online.

That's the theory, at least. The empirical research on so-called echo chambers is mixed. Facebook's data scientists have run large studies on the idea and found it wanting. The social networking company says that by exposing you to more people, Facebook adds diversity to your news diet.

Others disagree. A study published last year by researchers at the IMT School for Advanced Studies Lucca, in Italy, found that homogeneous online networks help conspiracy theories persist and grow online.

"This creates an ecosystem in which the truth value of the information doesn't matter," said Walter Quattrociocchi, one of the study's authors. "All that matters is whether the information fits in your narrative."

Digital technology has blessed us with better ways to capture and disseminate news. There are cameras and audio recorders everywhere, and as soon as something happens, you can find primary proof of it online.

You would think that greater primary documentation would lead to a better cultural agreement about the "truth." In fact, the opposite has happened.

Consider the difference in the examples of the John F. Kennedy assassination and 9/11. While you've probably seen only a single film clip of the scene from Dealey Plaza in 1963 when President Kennedy was shot, hundreds of television and amateur cameras were pointed at the scene on 9/11. Yet neither issue is settled for Americans; in one recent survey, about as many people said the government was concealing the truth about 9/11 as those who said the same about the Kennedy assassination.

Documentary proof seems to have lost its power. If the Kennedy conspiracies were rooted in an absence of documentary evidence, the 9/11 theories benefited from a surfeit of it. So many pictures from 9/11 flooded the internet, often without much context about what was being shown, thatconspiracy theorists could pick and choose among them to show off exactly the narrative they preferred. There is also the looming specter of Photoshop: Now, because any digital image can be doctored, people can freely dismiss any bit of inconvenient documentary evidence as having been somehow altered.

This gets to the deeper problem: We all tend to filter documentary evidence through our own biases. Researchers have shown that two people with differing points of view can look at the same picture, video or document and come away with strikingly different ideas about what it shows.

That dynamic has played out repeatedly this year. Some people look at the WikiLeaks revelations about Mrs. Clinton's campaign and see a smoking gun, while others say it's no big deal, and that besides, it's been doctored or stolen or taken out of context. Surveys show that people who liked Mr. Trump saw the Access Hollywood tape where he casually referenced groping women as mere "locker room talk"; those who didn't like him considered it the worst thing in the world.