Ads attacking Barack Obama more frequently depicted him with darker skin, especially when they linked the president to crime, according to a study examining complexion in 2008 campaign commercials.
The research, conducted by the Pew Research Center and published online this month in Public Opinion Quarterly, also found that the negative ads with darker images aired more often as Election Day approached.
The study, which the researchers said was meant to investigate how the “strong evidence linking skin complexion to negative stereotypes” extends to political campaigns, comes as the current presidential debate grapples with racial issues. Supporters of Republican candidate Donald Trump, for example, have clashed with protestors advocating the Black Lives Matter movement.
The study found the darkest images of Obama appear in the most negative, stereotype-consistent ads. In attack ads that associated Obama with alleged criminal activity by leftists, the probability that the ad contained one of the darkest images was three times higher than for other ads.
As the election approached, attack ads featured images with darker depictions of Obama. However, on average the images did not change much overall, likely due to other images growing lighter as well.
The researchers noted shortfalls of the study. They couldn’t measure whether complexion in ads were intentional, and their analysis didn’t examine photographic contrast as an element of lightness or darkness of an image. The study also only examined still images and captures from video, but didn’t examine video clips.