People who think television is worthless have been known to dismiss it as the "idiot box." But maybe they should amend that and call it the racist idiot box?

According to a new study, watching a lot of news might make you more biased against African Americans.

The main researcher, Temple Northup, a professor of communications at the University of Houston, explained that this is probably because local news coverage tends to focus on crime, and when it comes to this crime coverage, stations cover crimes committed by black people in ways that are way out of proportion with their actual crime rates.

More news = more unconscious racial bias

The study, published recently in the International Journal of Communication, was very small — this portion of it only had 316 participants. But its results were compelling.

The researchers gave their subjects a questionnaire about their attitudes toward African Americans, and on how many hours of local news they watched each day. Subjects also took the Implicit Association Test (IAT), a tool Anthony Greenwald and his colleagues invented in the mid-1990s that's used to measure unconscious racial bias by capturing the beliefs about different groups that people hold but would never admit to.

An organization called Project Implicit, maintained by Greenwald, Mahzarin Banaji, and Brian Nosek, allows people to take the IAT online. It's a bit like a computer game, the object of which is to sort categories of pictures and words.

Here's an example of how it measures implicit racial bias: in the black-white race attitude test, test takers are asked to sort pictures of white and black people's faces, and positive and negative words, by pressing one of two keys on the keyboard. It turns out that most people are able to do this more quickly when the white faces and positive words are assigned to the same key (black faces and negative words are assigned to the other key), compared with when white faces and negative words are assigned to the same key and black faces and positive words are assigned to the other key. The difference in the time it takes a user to respond in different situations is the measure of implicit bias.

In Northup's study, the results were revealing. "Based on the findings from the study in the U.S., long-term exposure to local television news, wherein African-Americans are depicted frequently and stereotypically as criminals, predicted increased negative implicit attitudes toward African-Americans," said Northup in a press release about the study. "Viewers who watched more local television news demonstrated more unconscious negative attitudes toward African-Americans."

Interestingly, when the researchers tried to replicate the study in Austria using exposure to tabloid-style newspapers, they didn't get the same connection between news consumption and implicit racial bias. They theorized that this was because readers can pick and choose which stories to focus on, while television viewers take in whatever is on the screen.

"Unlike with television news, though, people have much more control over a printed newspaper because they are able to selectively expose themselves only to stories of interest," Northup said.

Yes, news has a racial bias

It's easy to think that news is an objective summary of the important events that have happened on a particular day, but that's not the case. The decisions about which stories to cover are made by humans — many of whom carry their own racial bias that they may not even be aware of.

The study authors cited previous research indicating that crime is overrepresented on local television news relative to the actual amount of crime that actually occurs in a community, and that within this crime coverage, black Americans are overrepresented as criminals compared with their actual crime rates.

Similarly, progressive research center Media Matters found, according to a report released in March, that New York City television stations give disproportionate coverage to crimes involving black suspects.

The Media Matters study found that between August 18, 2014, and December 13, 2014, the stations (WCBS, WNBC, WABC, and WNYW) used their late-night broadcasts to report on murder, theft, and assault cases in which African Americans were suspects at rates that far exceeded African-American arrest rates for those crimes.

According to New York City Police Department statistics, African Americans were suspects in 54 percent of murders, 55 percent of thefts, and 49 percent of assaults. But the suspects in the stations' coverage were black in 74 percent of murder stories, 84 percent of theft stories, and 73 percent of assault stories.

"This type of overrepresentation sends a message that it's okay and it's justified to fear black folks. It sends a message about who black people are that is harmful and hurtful," said Rashad Robinson, executive director of the civil rights group ColorOfChange.

Northup, taking a positive view of the somewhat disturbing results of his study, said he hopes the results will contribute to a better understanding and awareness of how watching television news coverage may lead to a negative racial bias, which in turn can lead to other negative outcomes, such as discriminatory behaviors.