Neuropolitics: Twenty years later.

Neuropolitics is the intersection of neuroscience and political science, and it has the interdisciplinary goal of transforming both disciplines. This article reviews the past 20 years of work in the field, identifying its roots, some overarching themes-reactions to political attitudinal questions and candidates faces, identification of political ideology based on brain structure or reactivity to nonpolitical stimuli, and racial attitudes-and obstacles to its progress. I then explore the methodological and analytical advances that point the way forward for the future of neuropolitics. Although the field has been slow to develop compared with neurolaw and neuroeconomics, innovations look ripe for dramatically improving our ability to model political behaviors and attitudes in individuals and predict political choices in mass publics. The coming advancements, however, pose risks to our current norms of democratic deliberation, and academics need to anticipate and mitigate these risks.

Red brain, blue brain: evaluative processes differ in Democrats and Republicans.

Liberals and conservatives exhibit different cognitive styles and converging lines of evidence suggest that biology influences differences in their political attitudes and beliefs. In particular, a recent study of young adults suggests that liberals and conservatives have significantly different brain structure, with liberals showing increased gray matter volume in the anterior cingulate cortex, and conservatives showing increased gray matter volume in the in the amygdala. Here, we explore differences in brain function in liberals and conservatives by matching publicly-available voter records to 82 subjects who performed a risk-taking task during functional imaging. Although the risk-taking behavior of Democrats (liberals) and Republicans (conservatives) did not differ, their brain activity did. Democrats showed significantly greater activity in the left insula, while Republicans showed significantly greater activity in the right amygdala. In fact, a two parameter model of partisanship based on amygdala and insula activations yields a better fitting model of partisanship than a well-established model based on parental socialization of party identification long thought to be one of the core findings of political science. These results suggest that liberals and conservatives engage different cognitive processes when they think about risk, and they support recent evidence that conservatives show greater sensitivity to threatening stimuli.

On social attribution: implications of recent cognitive neuroscience research for race, law, and politics.

Interpreting the world through a social lens is a central characteristic of human cognition. Humans ascribe intentions to the behaviors of other individuals and groups. Humans also make inferences about others' emotional and mental states. This capacity for social attribution underlies many of the concepts at the core of legal and political systems. The developing scientific understanding of the neural mechanisms used in social attribution may alter many earlier suppositions. However, just as often, these new methods will lead back to old conundrums. Cognitive neuroscience will not dispel the hard problems of social judgment.

Neural basis of egalitarian behavior.

Individuals are willing to sacrifice their own resources to promote equality in groups. These costly choices promote equality and are associated with behavior that supports cooperation in humans, but little is known about the brain processes involved. We use functional MRI to study egalitarian preferences based on behavior observed in the "random income game." In this game, subjects decide whether to pay a cost to alter group members' randomly allocated incomes. We specifically examine whether egalitarian behavior is associated with neural activity in the ventromedial prefrontal cortex and the insular cortex, two regions that have been shown to be related to social preferences. Consistent with previous studies, we find significant activation in both regions; however, only the insular cortex activations are significantly associated with measures of revealed and expressed egalitarian preferences elicited outside the scanner. These results are consistent with the notion that brain mechanisms involved in experiencing the emotional states of others underlie egalitarian behavior in humans.

Biology, politics, and the emerging science of human nature.

In the past 50 years, biologists have learned a tremendous amount about human brain function and its genetic basis. At the same time, political scientists have been intensively studying the effect of the social and institutional environment on mass political attitudes and behaviors. However, these separate fields of inquiry are subject to inherent limitations that may only be resolved through collaboration across disciplines. We describe recent advances and argue that biologists and political scientists must work together to advance a new science of human nature.