In two large survey experiments we investigated two mechanisms that might trigger motivated political reasoning and exacerbate attitude polarization: (1) relational motives to establish within-group homogeneity, manipulated with in-group and out-group cues, and (2) epistemic motivates to reduce uncertainty, manipulated by raising uncertainty about politically relevant evidence. Because conservatives generally exhibit stronger epistemic and relational motives than liberals, we investigated whether these mechanisms would contribute to asymmetric polarization. Results of the experiment revealed that when liberal and conservative respondents were exposed to social cues indicating where the two groups stood on specific issues, their attitudes polarized, but conservatives polarized to a larger degree. Increasing uncertainty did not exacerbate attitude polarization, but conservatives displayed stronger confirmation bias in the evaluation of political arguments when uncertainty was high (vs. low), whereas liberals did not. Implications for the study of ideology in motivated political reasoning are discussed.