The skin tone in images came up during the Democratic primaries of the 2008 presidential campaign. Hillary Clinton's campaign came under fire from the liberal blogosphere for putting out a television ad attacking Obama that some believed portrayed the candidate with a darker skin tone. Likewise, Time Magazine was once criticized for darkening O.J. Simpson's skin color for its cover picture.
Killen also expressed concern about the small sample size of the study and its failure to address the background of the participants.
"It's not about 'people' -- it's about the white majority, high status," said Killen, a developmental psychologist. "It's one thing if you're looking at eye blinking or memory in a study, but you're looking at issues of race and ethnicity. Don't you need to know the ethnicity of the participants?"
When asked by ABC News about the race and ethnicity of the participants, Caruso acknowledged the limitation.
"We did ask participants to indicate their race at the end of the study and we were hoping that we'd be able to test for differences. Unfortunately, fewer than 10 percent of our participants identified as being black, so we didn't have enough power to test between black and non-black participants," Caruso said.
Caruso maintains that the study brings further fuel to the field of research to explore how political beliefs can effect one's perception of the world.
"Part of my research interest more generally is in how people come to understand the perception of someone who might be different than them." he said. "People generally have a hard time coming to grips with or coming to understand how someone's attitude differs from their own. So this was a step to see some of the depth of some of that difficulty."