Monday, October 23, 2006

Imaging the brain during the motivated reasoning of political bias

Westen et al. report studies using functional neuroimaging to study the neural responses of 30 committed partisans during the U.S. Presidential election of 2004. They presented subjects with reasoning tasks involving judgments about information threatening to their own candidate, the opposing candidate, or neutral control targets. Motivated reasoning was associated with activations of the ventromedial prefrontal cortex, anterior cingulate cortex, posterior cingulate cortex, insular cortex, and lateral orbital cortex. As predicted, motivated reasoning was not associated with neural activity in regions previously linked to cold reasoning tasks and conscious (explicit) emotion regulation. The findings provide the neuroimaging evidence for phenomena variously described as motivated reasoning, implicit emotion regulation, and psychological defense. They suggest that motivated reasoning is qualitatively distinct from reasoning when people do not have a strong emotional stake in the conclusions reached.

Figure legend - Subjects' ratings of perceived contradictions in statements by Bush, Kerry, and neutral figures (higher ratings indicate greater perceived contradictions). Democrats and Republicans reasoned to distinctly different conclusions about their preferred candidates, with mirror-image responses: Democrats readily identified the contradictions in Bush's statements but not Kerry's, whereas Republicans readily identified the contradictions in Kerry's statements but not Bush's. In contrast, Democrats and Republicans reasoned similarly about the contradictions of politically neutral figures.

One of several figures showing imaging data - Three orthogonal views (axial, sagittal, coronal) of the areas of activation that differed when subjects were confronted with contradictory (threatening) information regarding their own party's candidate versus a neutral target person. ACC = anterior cingulate; mPFC = medial prefrontal cortex; pCING = posterior cingulate; PCU = precuneus; vmPFC = ventromedial prefrontal cortex.

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