Your brain’s response to viewing images such as maggot infestations, rotting carcasses, dirty unflushed toilets, unidentifiable gunk in the kitchen sink, and suchlike can predict with amazing accuracy where you will fit into the liberal/conservative political dialectic. That’s according to a study published in the upcoming issue of the journal Current Biology, in which an international team of scientists reports that the strength of a person’s reaction to repulsive images can forecast their political ideology.
In their Open Access Current Biology paper, entitled “Nonpolitical images evoke neural predictors of political ideology.” (DOI: http://dx.doi.org/10.1016/j.cub.2014.09.050), coauthored by Woo-Young Ahn, Kenneth T. Kishida, Xiaosi Gu, Terry Lohrenz, Ann Harvey, John R. Alford, Kevin B. Smith, Gideon Yaffe, John R. Hibbing, Peter Dayan, and P. Read Montague — variously of Virginia Tech Carilion Research Institute, University College London, Rice University, the University of Nebraska at Lincoln, and Yale University — say that in a brain scanner, participants were shown disgusting images, such as rotting flesh or mutilated carcasses, mixed with neutral and pleasant images, such as landscapes and babies.
Afterward, the subjects completed a behavioral rating session in which they rated all pictures they had seen in the scanner (using a nine-point Likert scale) as disgusting, threatening, or pleasant. Lastly, participants filled out computer-based questionnaires assessing their political attitudes, disgust sensitivity, and state/trait anxiety level. In a standard political ideology inventory they answered questions about how often they discuss politics and whether they agreed or disagreed with hot-button topics such as school prayer and gay marriage. Using functional magnetic resonance imaging, the scientists recorded brain activity of the subjects responding to the images.
They found that responses to disgusting images could predict, with 95 percent to 98 percent accuracy, how a person would answer questions on the political survey. Political ideology was summed from several survey items including ideological position, partisan affiliation, and policy preferences (e.g., gun control and immigration, presented in the well-known Wilson-Patterson format. Survey items on political ideology were normalized continuously from 0 (extremely liberal) to 1 (extremely conservative).
The researchers note that 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. However, despite the abstract nature of such sensibilities, fundamental features of political ideology have been found to be deeply connected to basic biological mechanisms that may serve to defend against environmental challenges like contamination and physical threat.
They observe that 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), and that their results have important implications for the links between biology, emotions, political ideology, and human nature more fundamentally. While previous studies using skin conductance response, neuroimaging, and questionnaire measures suggested the role of emotions in political attitudes, to their 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.
The coauthors note that accumulating evidence suggests that cognition and emotion are deeply intertwined, and a view of segregating cognition and emotion is becoming obsolete. They recognize that people tend to think that their political views are purely cognitive (i.e., rational), but say their results further support the notion that emotional processes are tightly coupled to complex and high-dimensional human belief systems, and such emotional processes might play a much larger role than we currently believe, possibly outside our awareness of its influence.
The researchers acknowledge that 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, that the theoretical basis for expecting biology to be relevant is weak and murky, that acknowledging a role for biology is reductionist, and that recognizing the relevance of biology to human beliefs and behaviors is potentially dangerous. THey express hope that some of this skepticism can be alleviated from their demonstration that fMRI data, even from a single stimulus, can serve as a strong predictor of political ideology.
They 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. They discovered that 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,” they say, “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.”
“Disgusting images generate neural responses that are highly predictive of political orientation even when those neural responses don’t correspond with an individuals conscious reaction to the images, says Dr. Read Montague, a Virginia Tech Carilion Research Institute professor who led the study. Remarkably, we found that the brains response to a single disgusting image was enough to predict an individuals political ideology.
“The results suggest political ideologies are mapped onto established neural responses that may have served to protect our ancestors against environmental threats,” says Dr. Montague in a Virginia Tech release. “Those neural responses could be passed down family lines; it’s likely that disgust reactions are inherited.
“We pursued this research because previous work in a twin registry showed that political ideology — literally the degree to which someone is liberal or conservative — was highly heritable, almost as heritable as height,” continues Dr. Montague, who directs the Computational Psychiatry Unit at the Virginia Tech Carilion Research Institute. “Conservatives tend to have more magnified responses to disgusting images, but scientists don’t know exactly why. The responses could be a callback to the deep, adverse reactions primitive ancestors needed to avoid contamination and disease. To prevent unsavory consequences, they had to learn to separate the canteen from the latrine.”
How Conservatives & Liberals’ Brains React To Disgusting Images
The paper coauthors acknowledge that while their results suggest that disgusting pictures evoke very different emotional processing in conservatives and liberals, it will take a range of targeted studies in the future to determine the separate contribution of each brain circuit. They propose that conservatives, compared to liberals, have greater negativity bias, which includes both disgusting and threatening conditions in the study. They suggest that their finding that only disgusting pictures, especially in the animal-reminder category, differentiate conservatives from liberals might be indicative of a primacy for disgust in the pantheon of human aversions, but it is also possible that this result is due to the fact that, compared to threat, disgust is much easier to evoke with visual images on a computer screen.
Several important questions remain unaddressed, such as while political ideology has effects on many forms of behavior (including, but not limited to, voting behavior), it is unknown whether it does so due to neural differences in affective processing the researchers measured. Relatedly, the coauthors observe that it is important also to know how individual differences in the capacity to regulate emotion, and the neural bases of that capacity, are related to political ideology. Another set of questions concerns the bearing of the present study on the development of biological measures of political ideology. They note that while it is of use in a variety of settings to measure political ideology (political polls, for instance, typically include some measurement of it), it remains an open question whether biological measures could become more accurate, or more useful, than the tools (such as self-report measures) currently employed. They agree that determining the answer to that question would require answering a host of others, such as how would a machine-learning model based on data collected in one region (e.g., New York) support predictions of people’s political attitudes in another region (e.g., Texas)? How fine-grained are the categories of affective response that are tied to political ideology?
And while their results show greater differentiation in political ideology in cases of animal-reminder disgust than core/contamination disgust, it remans to be determined what links there are between political ideology and other forms of disgust, such as moral disgust.
Dr. Montague points out that we’re not necessarily hardwired to respond on instinct alone. Using height as an analogy, he observes that while genetics partly predetermine height, nutrition, sleep, and starvation can all be contributory factors in determining how tall an individual will ultimately grow. Nevertheless, tall people’s children tend to be tall, and that’s a kind of starting point, Dr. Montague notes. “If we can begin to understand that some automatic reactions to political issues may be simply that: reactions, then we might take the temperature down a bit in the current boiler of political discourse.”
He also observes that human beings are unique among animals in their degree of cognitive control, or what he calls “behavioral superpower” by which they can deny or override their biological instincts in service of an idea or ideology. Examples would be hunger strikes for political reasons, Dr. Montague said, which require a high degree of cognitive control, and that’s the point. We need to think; not just react.
In their paper, Dr. Montague and his colleagues conclude that the more we learn about the sensitivity of political ideology to subtle differences in affective response and their neural bases, the more we will know about the feasibility of useful and portable tools for ideology’s biological measurement. This would then raise a further and difficult ethical question about the circumstances, if any, in which it is appropriate to use such tools. And, finally, the present study raises important questions about the possibility of, and obstacles to, understanding and cooperation across divides in political ideology. Would recognition that those with different political beliefs from our own also exhibit different disgust responses from our own help us or hinder us in our ability to embrace them as coequals in democratic governance? The scientists conclude that future work will be necessary to answer these important questions.
Dr. Read Montague’s work centers broadly on human social cognition, decision-making, and willful choice with a goal of understanding the detailed underlying neurobiology of these functions in health and disease.
Dr. Montague’s research particularly focuses on computational neuroscience the connection between physical mechanisms present in real neural tissue and the computational functions that these mechanisms embody. His laboratory uses theoretical, computational, and experimental approaches to these issues. In particular, the group now employs novel approaches to functional neuroimaging, new biomarkers for mental disease, spectroscopy, real-time voltammetry, and computational simulations.
Dr. Montague also directs the Roanoke Brain Study, a project aimed at understanding decision-making through the lifespan and its relationship to brain development, function, and disease. Work in the Montague laboratory is supported by the National Institutes of Health, National Science Foundation, The Kane Family Foundation, Autism Speaks, The MacArthur Foundation, The Dana Foundation, and the Wellcome Trust, and the Wellcome Trust Principal Research Fellowship, the Gatsby Charitable Trust, the National Science Foundation, and the Kane Family Foundation supported the research reported in the Current Biology paper.
The Virginia Tech Carilion Research Institute joins the life science, physical science, computational science, informatics, engineering, and social science strengths of Virginia Tech with the medical education expertise of the Virginia Tech Carilion School of Medicine and the medical practice experience of Carilion Clinic.