In 1994 Time magazine ran a controversial cover photo of O.J. Simpson’s mugshot that, to some readers, seemed to have been intentionally altered to make Simpson’s skin look darker than normal. Accompanied by the headline “An American Tragedy,” Time was criticized for manipulating Simpson’s appearance to make him seem menacing, and therefore more likely to be guilty of his accused crimes. People were so upset by the image that James Gaine, then the magazine’s managing editor, issued a public apology.

Recent research suggests that people do have a proclivity to perceive someone with darker skin as more likely to have committed an immoral act, regardless of the person’s race. Dubbing this tendency the “bad is black” effect, professor Adam Alter of New York University, along with three of his colleagues, conducted six studies showing a link between skin tone and perceptions of whether a person committed a criminal act.

In two initial studies, the researchers specifically looked at whether the media tends to run darker photographs of celebrities and politicians when writing about their transgressions. In one study, they created a database of online news articles about a set of highly popular White and Black celebrities, of both genders, during the time period 2011 through 2013. Trained research assistants coded a sample of the articles to determine whether the written content of each article was mostly negative, neutral, or positive. In addition, research assistants also coded the skin tone of the photograph accompanying each article on a scale ranging from dark to light. Since photographs can differ in a number of other important ways, the assistants also coded how well the photograph had been technically executed, for example, how fuzzy or clear the image appeared. In addition, they coded the overall quality of the celebrity’s physical appearance in the photo, such as how well-dressed and put-together they seemed. After statistically controlling for the ratings of quality of the image, the researchers discovered a relationship between the written content of an article and the skin tone in the accompanying photograph: Articles containing negative content were more likely to appear alongside darker colored photographs.

In another study, the researchers replicated these with a set of news articles about politicians. After compiling a list of Black and White members of Congress and Cabinet members from 1997 through 2014, research assistants similarly coded the written content of the articles as well as the accompanying photographs. Once again, after controlling for ratings of quality and appearance of the photograph, negative articles were more likely to be run alongside darker colored images. This was true regardless of the politician’s race or gender. Why would the media tend to choose darker photographs when writing about negative behavior? The answer may lie in a pervasive belief that darkness and badness tend to go together.

The researchers demonstrated this psychological link between darkness and badness by running several experiments where participants were asked to choose between headshots to identify a perpetrator. Online participants first examined two different grainy video surveillance images, alongside a brief sentence describing what the man in each image was doing either before or after the image was taken. For one image, they were told that the man had committed a virtuous act, such as risking his life to save someone, or establishing a charity for children. For the other image, they were told the man had committed an immoral act such as murder or abuse. After viewing each image and description, participants were shown two headshots of different men. One headshot had been artificially darkened and the other artificially lightened. Participants indicated which of the headshots represented the man who appeared in each surveillance image on a scale ranging from 1 (definitely Person A) to 6 (definitely Person B).

In addition to choosing between headshots, participants were asked to indicate the “color of the soul” of each man in the surveillance images. (“Soul color” could act as a metaphorical representation of how closely participants associate visual color with badness, apart from either skin tone or race.) Using a color spectrum ranging from black to white, participants clicked on the color shade that seemed to represent the color of the man’s soul who had committed the moral act as well as the color of the man’s soul who had committed the immoral act. Finally, the researchers measured participants’ racial attitudes through a separate survey. Participants were asked how warmly they felt towards White Americans as well as towards various dark skinned minorities, such as African Americans and Muslim Americans.

The researchers found that participants who held more negative attitudes towards darker skinned minorities, such as African Americans, were more likely to choose the darker photograph when asked who committed the immoral act. This finding in itself is perhaps unsurprising. A more startling pattern emerged when the researchers analyzed people’s headshot choices based on what “color” they thought the men’s souls were. Even after statistically controlling for participants’ racial attitudes, the researchers found that participants who thought the man who committed the immoral act had a darker colored soul were also more likely to think he had darker colored skin. In other words, regardless of race, dark skin was associated with evil in the minds of people who saw a link between darkness and badness.

Although psychologists have known for a long time that people associate dark skin with negative personality traits, this research shows that the reverse is also true: when we hear about an evil act, we are more likely to believe it was done by someone with darker skin. This “bad is black” effect may have its roots in our deep-seated human tendency to associate darkness with wickedness. Across time and cultures, we tend to portray villains as more likely to be active during nighttime and to don black clothing. Similarly, our heroes are often associated with daytime and lighter colors. These mental associations between color and morality may negatively bias us against people with darker skin tones. If this is true, it has far-reaching implications for our justice system. For example, eye witnesses to crimes may be more likely to falsely identify suspects who possess darker skin.

Overall, the “bad is black” effect only underscores the importance of finding ways to combat the various ways that our inherent biases can influence perceptions of guilt and innocence. Understanding the extent of these biases, as well as what may be causing them, represents an important first step.