13 peer-reviewed studies show liberals and conservatives physiologically different.
In the 13 peer-reviewed scientific studies summarized below, researchers found that liberals and conservatives have different brain structures, different physiological responses to stimuli, and activate different neural mechanisms when confronted with similar situations. Each entry below references the source document, and in most cases, a PDF of the study has been included. The studies are arranged from most recent to oldest. We included all the peer-reviewed studies on this subject which we could find.
1. Conservatives spend more time looking at unpleasant images, and liberals spend more time looking at pleasant images.
"We report evidence that individual-level variation in people's physiological and attentional responses to aversive and appetitive stimuli are correlated with broad political orientations. Specifically, we find that greater orientation to aversive stimuli tends to be associated with right-of-centre and greater orientation to appetitive (pleasing) stimuli with left-of-centre political inclinations."
Michael D. Dodd, Amanda Balzer, Carly Jacobs, Michael Grusczynszyki, Kevin B. Smith, and John R. Hibbing, "The Left Rolls with the Good; The Right Confronts the Bad. Physiology and Cognition in Politics," rstb.royalsocietypublishing.org, Mar. 5, 2012
2. Reliance on quick, efficient, and "low effort" thought processes yields conservative ideologies, while effortful and deliberate reasoning yields liberal ideologies.
"...[P]olitical conservatism is promoted when people rely on low-effort thinking. When effortful, deliberate responding is disrupted or disengaged, thought processes become quick and efficient; these conditions promote conservative ideology… low-effort thought might promote political conservatism because its concepts are easier to process, and processing fluency increases attitude endorsement.
Four studies support our assertion that low-effort thinking promotes political conservatism... Our findings suggest that conservative ways of thinking are basic, normal, and perhaps natural."
Scott Eidelman, Christian S. Crandall, Jeffrey A. Goodman, and John C. Blanchar, "Low-Effort Thought Promotes Political Conservatism,"PDF logo Society for Personality and Social Psychology, 2012
3. Conservatives react more strongly than liberals to disgusting images, such as a picture of someone eating worms.
This image of a man eating worms is similar to one that was shown to subjects in the study. Source: Kevin B. Smith, et al., 'Disgust Sensitivity and the Neurophysiology of Left-Right Political Orientations,' www.plosone.org, Oct. 19, 2011"People who believe they would be bothered by a range of hypothetical disgusting situations display an increased likelihood of displaying right-of-center rather than left-of-center political orientations… In this article, we demonstrate that individuals with marked involuntary physiological responses to disgusting images [measured by change in mean skin conductance], such as of a man eating a large mouthful of writhing worms, are more likely to self-identify as conservative and, especially, to oppose gay marriage than are individuals with more muted physiological responses to the same images."
Kevin B. Smith, Douglas Oxley, Matthew V. Hibbing, John R. Alford, and John R. Hibbing, "Disgust Sensitivity and the Neurophysiology of Left-Right Political Orientations,"PDF logo www.plosone.org, Oct. 19, 2011
4. Liberals have more tolerance to uncertainty (bigger anterior cingulate cortex), and conservatives have more sensitivity to fear (bigger right amygdala).
Source: Gary Leisman, et al., 'Intentionality and 'Free-Will' from a Neurodevelopmental Perspective,' www.frontiersin.org, June 27, 2012
"In a large sample of young adults, we related self-reported political attitudes to gray matter volume using structural MRI [magnetic resonance imaging]. We found that greater liberalism was associated with increased gray matter volume in the anterior cingulate cortex, whereas greater conservatism was associated with increased volume of the right amygdala...
...[O]ur findings are consistent with the proposal that political orientation is associated with psychological processes for managing fear and uncertainty. The amygdala has many functions, including fear processing. Individuals with a larger amygdala are more sensitive to fear, which, taken together with our findings, might suggest the testable hypothesis that individuals with larger amagdala are more inclined to integrate conservative views into their belief systems... our finding of an association between anterior cingulate cortex [ACC] may be linked with tolerance to uncertainty. One of the functions of the anterior cingulate cortex is to monitor uncertainty and conflicts. Thus it is conceivable that individuals with a larger ACC have a higher capacity to tolerate uncertainty and conflicts, allowing them to accept more liberal views."
Ryota Kanai, Tom Feilden, Colin Firth, and Geraint Rees, "Political Orientations Are Correlated with Brain Structure in Young Adults,"PDF logo Current Biology, Apr. 7, 2011
5. Conservatives have stronger motivations than liberals to preserve purity and cleanliness.
"...[R]eminders of physical purity influence specific moral judgments regarding behaviors in the sexual domain as well as broad political attitudes...
...[E]nvironmental reminders of physical cleanliness shifted participants’ attitudes toward the conservative end of the political spectrum and altered their specific attitudes toward various moral acts... When taken together, these two sets of results point to the possibility that political orientation may be, in some measure, shaped by the strength of an individual’s motivation to avoid physical contamination and that resulting vigilance for threats to purity may serve to reinforce a politically conservative stance toward the world."
Erik G. Helzer and David A. Pizarro, "Dirty Liberals! Reminders of Physical Cleanliness Influence Moral and Political Attitudes,"PDF logo Psychological Science, Mar. 18, 2011
6. Liberals follow the direction of eye movements better than conservatives.
Source: www.candleaac.com (accessed July 13, 2012)
"In the present study, we examine whether gaze cue effects [the ability to follow the direction of another individual’s eye movements or gaze] are moderated by political temperament, given that those on the political right tend to be more supportive of individualism—and less likely to be influenced by others—than those on the left. We find standard gaze cuing effects across all subjects, but systematic differences in these effects by political temperament. Liberals exhibit a very large gaze cuing effect while conservatives show no such effect at various SOAs [stimulus onset asynchrony]...
Perhaps conservatives are less likely to trust others meaning that they are also less likely to trust a gaze cue..."
Michael D. Dodd, John R. Hibbing, and Kevin B. Smith "The Politics of Attention: Gaze Cuing Effects Are Moderated by Political Temperament," PDF logo Attention, Perception & Psychophysics, Jan. 2011
7. Republicans are more likely than Democrats to interpret faces as threatening and expressing dominant emotions.
"Independent sample t-tests revealed group differences in the averaged threat interpretation scores of the 10 facial stimuli. Republican sympathizers were more likely to interpret the faces as signaling a threatening expression as compared to Democrat sympathizers. Group differences were also found for dominance perceptions, whereby Republican sympathizers were more likely to perceive the faces as expressing dominant emotions than were Democrat sympathizers..."Jacob M. Vigil, "Political Leanings Vary with Facial Expression Processing and Psychosocial Functioning,"PDF logo Group Processes & Intergroup Relations, 2010
8. When making risky decisions, Republicans consider external consequences (ventral anterior cingulate and bilateral amygdala) while Democrats weigh internal considerations (right insula).
"We matched public voter records to 54 subjects who performed a risk-taking task during functional imaging. We find that Democrats and Republicans had significantly different patterns of brain activation during processing of risky decisions.
...[I]t appears in our experiment that Republican participants, when making a risky choice, are predominantly externally oriented, reacting to the fear-related processes with a tangible potential external consequence. In comparison, risky decisions made by Democratic participants appear to be associated with monitoring how the selection of a risky response might feel internally."
Darren Schreiber, Alan N. Simmons, Christopher T. Dawes, Taru Flagan, James H. Fowler, and Martin P. Paulus, "Red Brain, Blue Brain: Evaluative Processes Differ in Democrats and Republicans," PDF logo American Political Science Association Toronto Meeting Paper, ssrn.com, Aug. 13, 2009
9. Genetics influence political attitudes during early adulthood and beyond.
"The present research attempts to characterize how the transmission of political orientations develops over the life course... [G]enetic influences on political attitudes are absent prior to young adulthood. During childhood and adolescence, individual differences in political attitudes are accounted for by a variety of environmental influences... However, at the point of early adulthood (in the early 20s), for those who left their parental home, there is evidence of a sizeable genetic influence on political attitudes which remains stable throughout adult life.”
Peter K. Hatemia, Carolyn L. Funka, Sarah E. Medlanda, Hermine M. Maesa, Judy L. Silberga, Nicholas G. Martina and Lindon J. Eavesa, "Genetic and Environmental Transmission of Political Attitudes Over a Life Time," The Journal of Politics, July 21, 2009
10. Compared to liberals, conservatives are less open to new experiences and learn better from negative stimuli than positive stimuli.
"In this study, the relations among political ideology, exploratory behavior, and the formation of attitudes toward novel stimuli were explored. Participants played a computer game that required learning whether these stimuli produced positive or negative outcomes. Learning was dependent on participants’ decisions to sample novel stimuli... Political ideology correlated with exploration during the game, with conservatives sampling fewer targets than liberals. Moreover, more conservative individuals exhibited a stronger learning asymmetry, such that they learned negative stimuli better than positive... Relative to liberals, politically conservative individuals pursued a more avoidant strategy to the game…
The reluctance to explore that characterizes more politically conservative individuals may protect them from experiencing negative situations, for they are likely to restrict approach to known positives.”
Natalie J. Shooka and Russell H. Faziob, "Political Ideology, Exploration of Novel Stimuli, and Attitude Formation,"PDF logo Experimental Social Psychology, Apr. 3, 2009
11. Conservatives tend to have a stronger reaction to threatening noises and images than liberals.
"In a group of 46 adult participants with strong political beliefs, individuals with measurably lower physical sensitivities to sudden noises and threatening visual images were more likely to support foreign aid, liberal immigration policies, pacifism, and gun control, whereas individuals displaying measurably higher physiological reactions to those same stimuli were more likely to favor defense spending, capital punishment, patriotism, and the Iraq War. Thus, the degree to which individuals are physiologically responsive to threat appears to indicate the degree to which they advocate policies that protect the existing social structure from both external (outgroup) and internal (norm-violator) threats."
Douglas R. Oxley, Kevin B. Smith, John R. Alford, Matthew V. Hibbing, Jennifer L. Miller, Mario Scalora, Peter K. Hatemi, and John R. Hibbing, "Political Attitudes Vary with Physiological Traits," Science, Sep. 19, 2008
12. Liberals are more open-minded and creative whereas conservatives are more orderly and better organized.
"We obtained consistent and converging evidence that personality differences between liberals and conservatives are robust, replicable, and behaviorally significant, especially with respect to social (vs. economic) dimensions of ideology. In general, liberals are more open-minded, creative, curious, and novelty seeking, whereas conservatives are more orderly, conventional, and better organized... A special advantage of our final two studies is that they show personality differences between liberals and conservatives not only on self-report trait measures but also on unobtrusive, nonverbal measures of interaction style and behavioral residue.”
Dana R. Carney, John T. Jost, Samuel D. Gosling, and Jeff Potter, "The Secret Lives of Liberals and Conservatives: Personality Profiles, Interaction Styles, and the Things They Leave Behind,"PDF logo International Society of Political Psychology, Oct. 23, 2008
13. When faced with a conflict, liberals are more likely than conservatives to alter their habitual response when cues indicate it is necessary.
"Our results are consistent with the view that political orientation, in part, reflects individual differences in the functioning of a general mechanism related to cognitive control and self-regulation. Stronger conservatism (versus liberalism) was associated with less neurocognitive sensitivity to response conflicts. At the behavioral level, conservatives were also more likely to make errors of commission. Although a liberal orientation was associated with better performance on the response-inhibition task examined here, conservatives would presumably perform better on tasks in which a more fixed response style is optimal."
David M. Amodio, John T. Jost, Sarah L. Master, and Cindy M. Yee, "Neurocognitive Correlates of Liberalism and Conservatism,"PDF logo Nature, Sep. 9, 2007
References: http://2012election.procon.org/view.resource.php?resourceID=004818
