51 Pages Posted: 15 Apr 2017

Date Written: April 13, 2017

Abstract

One form of partisan bias is the tendency to more readily accept the validity of information that affirms one’s political beliefs than information that challenges those beliefs. Both liberals and conservatives accuse their political opponents of partisan bias, but is there empirical evidence that one side of the political aisle is indeed more biased than the other? To address this question, we meta-analyzed the results of 41 experimental studies of partisan bias involving over 12,000 participants who identified their political ideology. Based on previous literature, two hypotheses were tested: an asymmetry hypothesis (predicting greater partisan bias in conservatives than liberals) and a symmetry hypothesis (predicting equal levels of partisan bias in liberals and conservatives). Overall partisan bias was robust (r = .254) and there was strong support for the symmetry hypothesis: liberals (r = .248) and conservatives (r = .247) showed nearly identical levels of bias across studies. Several methodological features moderated the degree of overall bias, and the relative magnitude of bias in liberals and conservatives differed across political topics. Implications of the current findings for the ongoing ideological symmetry debate, and partisan bias’ role in scientific discourse and political conflict are discussed.