Suppose, for instance, a study finds that conservatives are less likely to change their opinions on moral issues than liberals are when exposed to counterarguments. “The researchers could explain this as ‘conservatives are cognitively rigid, inflexible, and resistant to new arguments,’ ” said Eric Luis Uhlmann, a psychologist at INSEAD in Singapore and the study’s corresponding author. “However, they could just as easily have interpreted this as ‘liberals are wishy-washy, overly flexible, and don’t stand by their principles.’ ” Uhlmann and his colleagues asked participants to rate whether a study’s findings were equally discussed in relation to liberals and conservatives, or instead were pinned on one group over the other.

Sure enough, the abstracts more often explained their findings in terms of conservative ideas rather than liberal ones, and conservatives were described more negatively in the eyes of the raters.

The effect sizes they found were “not huge,” Uhlmann said, but they were present. “For a randomly chosen abstract there’s about a 60 percent chance of it describing liberals more favorably than conservatives, and a 56 percent chance of it explaining conservatives more,” he said. (If there were no difference, you’d expect both numbers to be 50 percent.)