This database also provides two novel measures: trust ratings of those articles by blind reviewers, who are significantly more impartial, and a comparison with the ratings of people with a normal news consumption experience that allows them to see the brand.

Consider that a reader’s trustworthy rating of a news article is the sum of the article’s inherent qualities, the reader’s personal views and brand prejudice. The experimental and control groups are alike, except that brand prejudice is removed from the experimental group. The difference in an article’s trustworthiness score between the two groups is equal to the brand prejudice — or bias — of the control group (those who can see the news source).

For those in that group, an individual’s bias was calculated for each article by taking the absolute value difference in trustworthiness ratings between his or her rating and the mean score for that article as provided by blind reviewers; the rating uses a scale of one to five, with increments of 0.5.

Who is at greatest risk of bias?

Among all readers in the group who could see the news source, 35 percent exhibit large bias — meaning their trust rating of an article diverged from the blind-review group by 1.5 points or more on the 1-to-5-point scale.

Not surprisingly, those with more extreme political views tend to provide more biased ratings of news. Those who described their political views as very liberal or very conservative exhibited large bias across 43 percent of the articles they rated, whereas those who described their views as moderate exhibited bias just 31 percent of the time. Likewise, those who leaned toward one party but did not fully identify with it exhibited about the same bias as the moderates.

The data also suggests that those who approve of President Trump rate news articles with more bias than those who disapprove of the president (39.2 percent versus 32.8 percent). However, Trump supporters tend to be less biased than those identifying as “very liberal.”