Abstract
SummaryPolitical ideologies summarize dimensions of life that define how a person organizes their public and private behavior, including their attitudes associated with sex, family, education, and personal autonomy [1, 2]. Despite the abstract nature of such sensibilities, fundamental features of political ideology have been found to be deeply connected to basic biological mechanisms [3, 4, 5, 6, 7] that may serve to defend against environmental challenges like contamination and physical threat [8, 9, 10, 11, 12]. These results invite the provocative claim that neural responses to nonpolitical stimuli (like contaminated food or physical threats) should be highly predictive of abstract political opinions (like attitudes toward gun control and abortion) [13]. We applied a machine-learning method to fMRI data to test the hypotheses that brain responses to emotionally evocative images predict individual scores on a standard political ideology assay. Disgusting images, especially those related to animal-reminder disgust (e.g., mutilated body), generate neural responses that are highly predictive of political orientation even though these neural predictors do not agree with participants’ conscious rating of the stimuli. Images from other affective categories do not support such predictions. Remarkably, brain responses to a single disgusting stimulus were sufficient to make accurate predictions about an individual subject’s political ideology. These results provide strong support for the idea that fundamental neural processing differences that emerge under the challenge of emotionally evocative stimuli may serve to structure political beliefs in ways formerly unappreciated.
Highlights
Participants filled out computer-based questionnaires assessing their political attitudes, disgust sensitivity, and state/trait anxiety level
While previous studies using skin conductance response [9,10,11], neuroimaging [21,22,23,24], and questionnaire [25, 26] measures suggested the role of emotions in political attitudes, to our knowledge, this is the first fMRI study revealing multivariate patterns of brain activity that differ between liberals and conservatives during emotional processing of sensory stimuli
Despite growing evidence from various fields, including genetics, cognitive neuroscience, and psychology, many political scientists remain skeptical of research connecting biological factors with political ideology, arguing variously that biology is irrelevant to central political questions [30], that the theoretical basis for expecting biology to be relevant is weak and murky [31], that acknowledging a role for biology is reductionist [32], and that recognizing the relevance of biology to human beliefs and behaviors is potentially dangerous [33]
Summary
Political ideologies summarize dimensions of life that define how a person organizes their public and private behavior, including their attitudes associated with sex, family, education, and personal autonomy [1, 2]. Despite the abstract nature of such sensibilities, fundamental features of political ideology have been found to be deeply connected to basic biological mechanisms [3,4,5,6,7] that may serve to defend against environmental challenges like contamination and physical threat [8,9,10,11,12] These results invite the provocative claim that neural responses to nonpolitical stimuli (like contaminated food or physical threats) should be highly predictive of abstract political opinions (like attitudes toward gun control and abortion) [13]. Brain responses to a single disgusting stimulus were sufficient to make accurate predictions about an individual subject’s political ideology These results provide strong support for the idea that fundamental neural processing differences that emerge under the challenge of emotionally evocative stimuli may serve to structure political beliefs in ways formerly unappreciated
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