I present to you a collection of research quotes on the topic of physiological (and non-physiological) differences between Republicans (or conservatives) and Democrats (or liberals). As far as I know, all the quotes are from credible and legitimate studies published by various academic journals. I will update this entry with further sources and quotes if I do additional research.
Latest update: August 3, 2012.
Latest update: August 3, 2012.
1. Chris Mooney stated the following in his article “How the Right-Wing Brain Works and What That Means for Progressives,” published by AlterNet on March 20, 2012.
"...what’s being called “morality” is emotional and, in significant part, automatic. It’s not about the conscious decisions you make about situations or policies—or at least, not primarily. Rather, the focus is on the unconscious impulses that shape how you think about situations before you’re even aware you’re doing so, and then guide (and bias) your reasoning."
2. Elisabeth Lyons posted the following in the press release "Political views are reflected in brain structure," published by EurikaAlert! on April 7, 2011.
"We all know that people at opposite ends of the political spectrum often really can't see eye to eye. Now, a new report published online on April 7th in Current Biology, a Cell Press publication, reveals that those differences in political orientation are tied to differences in the very structures of our brains."
"Individuals who call themselves liberal tend to have larger anterior cingulate cortexes, while those who call themselves conservative have larger amygdalas. Based on what is known about the functions of those two brain regions, the structural differences are consistent with reports showing a greater ability of liberals to cope with conflicting information and a greater ability of conservatives to recognize a threat, the researchers say."
"Previously, some psychological traits were known to be predictive of an individual's political orientation," said Ryota Kanai of the University College London. "Our study now links such personality traits with specific brain structure."
"Kanai said his study was prompted by reports from others showing greater anterior cingulate cortex response to conflicting information among liberals. "That was the first neuroscientific evidence for biological differences between liberals and conservatives,"
3. Ryota Kanai, Tom Feliden, and Colin Firth, stated the following in their report "Political Orientations Are Correlated with Brain Structure in Young Adults," published by the journal "Current Biology" on April 26, 2011.
"In a large sample of young adults, we related self-reported political attitudes to gray matter volume using structural MRI. 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..."
"Although political attitudes are commonly assumed to have solely environmental causes, recent studies have begun to identify biological inﬂuences on an individual’s political orientation..."
"...the amplitude of event-related potentials reﬂecting neural activity associated with conﬂict monitoring in the anterior cingulate cortex (ACC) is greater for liberals compared to conservatives . Thus, stronger liberalism is associated with increased sensitivity to cues for altering a habitual response pattern and with brain activity in anterior cingulate cortex...."
"Conservatives respond to threatening situations with more aggression than do liberals and are
more sensitive to threatening facial expressions. This heightened sensitivity to emotional faces suggests that individuals with conservative orientation might exhibit differences in brain structures associated with emotional processing such as the amygdala..."
"Although these results suggest a link between political attitudes and brain structure, it is important to note that the neural processes implicated are likely to reﬂect complex processes of the formation of political attitudes rather than a direct representation of political opinions per se..."
"...our 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 large amygdala are more sensitive to fear, which, taken together with our ﬁndings, might suggest the testable hypothesis that individuals with larger amygdala are more inclined to integrate conservative views into their belief system. Similarly, it is striking that conservatives are more sensitive to disgust, and the insula is involved in the feeling of disgust..."
"[it is difficult to] determine whether the changes in brain structure that we observed lead to changes in political behavior or whether political attitudes and behavior instead result in changes of brain structure"
4. Smith KB, Oxley D, Hibbing MV, Alford JR, and Hibbing JR, stated the following in their study "Disgust Sensitivity and the Neurophysiology of Left-Right Political Orientations," published by Plos One on October 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. Given its primal nature and essential value in avoiding pathogens disgust likely has an effect even without registering in conscious beliefs. In this article, we demonstrate that individuals with marked involuntary physiological responses to disgusting images, 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..."
"...people's physiological predispositions help to shape their political orientations..."
."..compared to people on the left, those on the right tended to report being more disgust sensitive..."
"It appears that those individuals who have the strongest physiological responses to an array of disgusting stimuli (none of which directly relates to sexuality or homosexuality) also tend to be the individuals who oppose gay marriage..."
"The central implication of our research is that, whether the relevant raw material of political attitudes is entirely environmental or partially innate, these attitudes sometimes become biologically instantiated in involuntary physiological responses to facets of life far detached from the political issues of the day..."
"To put it differently, the proper interpretation of the findings reported here is not that biology causes politics or that politics causes biology but that certain political orientations at some unspecified point become housed in our biology, with meaningful political consequences..."
5. Michael D. Dodd, Amanda Balzer, Carly Jacobs, Michael Grusczynszyki, Kevin B. Smith, and John R. Hibbing stated the following in their report "The Left Rolls with the Good; The Right Confronts the Bad. Physiology and Cognition in Politics," published by The Royal Society on March 15, 2012.
"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-center and greater orientation to appetitive (pleasing) stimuli with left-of-center political inclinations..."
"the hypothesis is that individuals on the right side of the political spectrum will exhibit increased electrodermal activity when viewing aversive images while those on the left side will exhibit increased electrodermal activity, in relative terms, when viewing the appetitive images..."
"in relative terms, individuals on the right spend a greater amount of time gazing at aversive
images while individuals on the left spend a greater amount of time gazing at appetitive
"Our core finding is that, compared to individuals on the political left, individuals on the right direct more of their attention to the aversive despite displaying greater physiological responsiveness to those stimuli..."
"...in spite of heightened physiological responses, individuals on the right often diligently attend to the aversive, which in turn is consistent with the fact that right-of-center policy positions are often designed to protect society against out-group threats (e.g., by supporting increased defense spending and opposing immigration) and in-group norm violators (e.g., by supporting traditional values and stern penalties for criminal behavior)..."
6. Douglas R. Oxley1, Kevin B. Smith1, John R. Alford, Matthew V. Hibbing, Jennifer L. Miller, Mario Scalora, Peter K. Hatemi and John R. Hibbing stated the following in their study "Political Attitudes Vary with Physiological Traits," published in the journal Science on September 19, 2008.
"We present evidence that variations in political attitudes correlate with physiological traits. 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..."
"Our findings suggest that political attitudes vary with physiological traits linked to divergent manners of experiencing and processing environmental threats."
7. Michael D. Dodd, John R. Hibbing, and Kevin B. Smith stated the following in their study "The Politics of Attention: Gaze cuing effects are moderated by political temperament," published by the University of Nebraska
"Gaze cues lead to reflexive shifts of attention even when those gaze cues do not predict target location. Though this general effect has been repeatedly demonstrated, not all individuals orient to gaze in an identical manner..."
"In the present study, we examine whether gaze cue effects 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..."
"One factor that may correlate with gaze cuing effects is the degree to which an individual values personal autonomy since an individual with this orientation may be less likely to be influenced by others. To examine this possibility, the present study investigates whether gaze cuing effects are moderated by political temperament. Individuals on the political right tend to be more supportive of individualism than those on the left..."
"One question that remains is why, exactly, conservatives are less susceptible to gaze cuing effects relative to liberals? We have argued that conservatives tend to value personal autonomy more so than liberals, making them less likely to be influenced by others and, in turn, less responsive to gaze cues..."
8. Darren Schreiber, Alan N. Simmons, Christopher T. Dawes, Taru Flagan, James H. Fowler, and Martin P. Paulus stated the following in their study "Red Brain, Blue Brain: Evaluative Processes Differ in Democrats and Republicans," published by the Social Science Research Network on August 13, 2009.
"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. Amygdala activations, associated with externally directed reactions to risk, are stronger in Republicans, while insula activations, associated with internally directed reactions to affective perceptions, are stronger in Democrats..."
"...a two parameter model of partisanship based on amygdala and insula activations achieves better accuracy in predicting whether someone is a Democrat or a Republican than a well established model in political science based on parental socialization of party identification..."
"Thus, it 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..."
"If Republicans are utilizing externally oriented processes in reacting to risks while Democrats are internally directed, then we would expect the one group to be more supportive of socially conservative policies and the other to be more sensitive to internal conflict..."
"Republicans and Democrats differ in the neural mechanisms activated while performing a risk-taking task. Republicans more strongly activate their ventral anterior cingulate and bilateral amgydala, associated with a more externally oriented reaction to risk. Democrats have higher activity in their right insula, associated with internally directed reactions to affective perceptions..."
9. Paul R. Nail, Ian McGregor, April E. Drinkwater, Garrett M. Steele, and Anthony W. Thompson stated the following in their study "Threat causes liberals to think like conservatives," published by the Journal of Experimental Psychology in July 2009.
"These findings indicate that threat drove liberals to shift toward social attitudes that are normally more characteristic of conservatives. Because the source of the threat and the measure of defensiveness were not closely related, these findings cannot be easily explained under a rational defensiveness framework..."
"The results of three studies support the reactive-liberals hypothesis. Liberals became more conservative following experimentally induced threats. In fact, the threats consistently caused liberals to become as conservative as conservatives chronically were. The findings of all three studies are consistent with the view that conservative social cognition, whether political or psychological, is a defensive reaction against feelings of personal vulnerability...
"We believe that political conservatism has psychological properties that make it particularly appealing when vulnerability is dispositionally or situationally salient. Moreover, defensive conservatism appears to be a general psychological response to vulnerability that is not necessarily strategically linked to the eliciting threats. We conclude that significant threats always induce a tendency towards conservative social cognition. Whether this tendency is manifested directly in terms of increased political conservatism, or more indirectly in terms of increased psychological conservatism, will depend upon the particulars of the situation..."
Scott Eidelman, Christian S. Crandall, Jeffrey A. Goodman, and John C. Blanchar, stated the following in their paper “Low-Effort Thought Promotes Political Conservatism,” published by the Society for Personality and Social Psychology in 2012.
“The authors test the hypothesis that low-effort thought promotes political conservatism. In Study 1, alcohol intoxication was measured among bar patrons; as blood alcohol level increased, so did political conservatism (controlling for sex, education, and political identification). In Study 2, participants under cognitive load reported more conservative attitudes than their no-load counterparts. In Study 3, time pressure increased participants’ endorsement of conservative terms. In Study 4, participants considering political terms in a cursory manner endorsed conservative terms more than those asked to cogitate; an indicator of effortful thought… Together these data suggest that political conservatism may be a process consequence of low-effort thought; when effortful, deliberate thought is disengaged, endorsement of conservative ideology increases.”
“…we develop the argument that political 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…”
“Bar patrons reported more conservative attitudes as their level of alcohol intoxication increased. Because alcohol limits cognitive capacity and disrupts controlled responding, while leaving automatic thinking largely intact, these data are consistent with our claim that low-effort thinking promotes political conservatism.”
“Participants under cognitive load reported more conservative attitudes than those not under cognitive load. Because cognitive load depletes available mental resources (Gilbert et al., 1988; Wegner & Erber, 1992), participants were left to draw more heavily on thinking that was easy and efficient… Cognitive load also produced a corresponding shift in liberal attitudes; when under load, participants’ endorsement of political liberalism decreased…”
Jacob M. Vigil stated the following in his study “Political leanings vary with facial expression processing and psychosocial functioning,” published in the journal Group Processes & Intergroup Relations in 2010.
“In the current study, I examined the hypothesis that political leanings reflect broader behavioral dispositions that are associated with individual differences in facial expression processing…”
“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…”
“In the current study, I show that individuals who sympathize with the Republican Party have a lower threshold for processing threatening stimuli from ambiguous social information as compared to sympathizers of the Democrat Party.”
Nicole A. Thomas, Tobias Loetscher, Danielle Clode, and Michael E. R. Nicholls stated the following in their study “Right-Wing Politicians Prefer the Emotional Left,” published by Plos One on May 2, 2012.
“Conservatives have heightened sensitivity for detecting emotional faces and use emotion more effectively when campaigning. As the left face displays emotion more prominently, we examined 1538 official photographs of conservative and liberal politicians from
Canada, the United Kingdom and the United States
for an asymmetry in posing. Across nations, conservatives were more likely than
liberals to display the left cheek. In contrast, liberals were more likely to
face forward than were conservatives. Emotion is important in political
campaigning and as portraits influence voting decisions, conservative
politicians may intuitively display the left face to convey emotion to voters…”
“…the left cheek is often displayed more prominently than the right cheek in portraits and photographs. This leftward bias is strongest when the model wants to display emotion, but is eliminated when concealing emotion. A number of studies have demonstrated that emotions are rated as more expressive when they are displayed on the left side of the face and individuals who are more emotionally expressive are more likely to present the left cheek when posing for a portrait… ”
“If conservatives are more predisposed to express and perceive emotion, they should be more likely to present the emotional left cheek more prominently in portraits…”
“If conservatives are more predisposed to express and perceive emotion, they should be more likely to present the emotional left cheek more prominently in portraits…”
“Overall, politicians were more likely to display the left cheek in their official photographs, consistent with prior reports of a leftward posing bias in portraiture. Interestingly, conservative politicians were significantly more likely to display the left cheek bias than were liberal politicians…”
“Liberals were more likely face forward than were conservatives. This could reflect a desire by liberal politicians to appear emotionally neutral as opposed to making use of emotion in their official photographs…”
“Given the predisposition of conservatives to express and use emotion, the preference to show the left cheek would allow conservatives to communicate emotions to voters through their portrait…”
“The current findings suggest that conservatives make better use of emotion than liberals by presenting the more emotional left cheek…”
Scott P. McLean, John P. Garza, Sandra A. Wiebe, Michael D. Dodd, Kevin B. Smith, John R. Hibbing, and Kimberly Andrews Espy stated the following in their study “The Differential Attention Biases of Conservatives and Liberals,” published by the University of Nebraska-Lincoln on April 27, 2011 on its website.
“In order to identify the relationship between people’s political orientation and their
tendency to focus attention on faces projecting particular emotions we turned to the flanker task. This paradigm seems particularly well-suited for testing the possibility that liberals and conservatives are differentially attentive to angry and to happy faces…”
“The flanker paradigm is a well-established research protocol for measuring attention…”
“…we adapted the flanker paradigm to determine whether differences across the political spectrum also exist in attention and emotion processing. The flanker paradigm makes it possible to investigate the effects of socially relevant stimuli (i.e., faces) on attention, in
different affective contexts. The question we pose is whether individuals holding policy
preferences traditionally associated with a conservative ideology as opposed to those holding liberal preferences will differ in their affect and congruity-relevant processing of information…”
“On average, when targets are angry, individuals with conservative issue positions have response times for incongruent flankers that are nearly as fast or even faster than for congruent flankers. Liberals, on the other hand, tend to be slowed down more by incongruent flankers as per traditional flanker effects. What this suggests is that conservatives focus so much on the target when it is angry that the usual slowing effects of incongruent flankers do not much apply. When only happy targets are analyzed, political ideology is completely unrelated, with a coefficient that is close to 0 (-.01) and statistically insignificant at even the .10 level…”
Luciana Carraro, Luigi Castelli, and Claudia Macchiella stated the following in their article “The Automatic Conservative: Ideology-Based Attentional Asymmetries in the Processing of Valenced Information,” published by Plos One on November 9. 2011.
“In the current work, we argued that political ideology is related to selective attention processes, so that negative stimuli are more likely to automatically grab the attention of conservatives as compared to liberals. In Experiment 1, we demonstrated that negative (vs. positive) information impaired the performance of conservatives, more than liberals, in an Emotional Stroop Task. This finding was confirmed in Experiment 2 and in Experiment 3 employing a Dot-Probe Task, demonstrating that threatening stimuli were more likely to attract the attention of conservatives. Overall, results support the conclusion that people embracing conservative views of the world display an automatic selective attention for negative stimuli…”
“Experiment 1 demonstrated that negative stimuli were more likely to grab the attention of conservatives, interfering with the execution of the primary task they had to perform (i.e., color-naming). Results from Experiment 2 and 3 further evidenced that ideology was related to spatial attention, and conservatives were more likely to quickly direct their attention toward negative images…”
“Thanks to attentional processes people filter the incoming information and left-right ideological differences appear to shape these early automatic processes. As a consequence, conservatives, as compared to liberals, may indeed build up discrepant representations of the world with the former being more biased toward negativity. The outcome of this automatic selective attention for threatening information, in turn, may then further increase the motivation to embrace ideological conservatism as a way to manage uncertainty and threat…”
Kevin B. Smith, Amanda J. Balzer, Michael W. Gruszczynski, Carly M. Jacobs, John R. Alford, Scott Stoltenberg, and John R. Hibbing stated the following in their study “Political Orientations May Vary with Detection of the Odor of Androstenone,” published by University of Nebraska-Lincoln on June 7, 2011 on its website.
“The particular social chemical analyzed in this study is androstenone, a nonandrogenic steroid found in the sweat and saliva of many mammals, including humans…”
“Only a few studies address androstenone‘s potential relevance to the broader (non-mating) aspects of social life…”
“…there may be grounds for speculating that those whose views are associated with the political right would also be more sensitive to the odor of androstenone, given that it seems to provide emotionally meaningful cues. Sensitivity to the emotional content of other people‘s odors, as well as to the emotional content of their faces, may be conducive to certain right-of-center political orientations…”
“A similar line of reasoning that leads to the same directional expectation is that, given its close relationship with testosterone, a substance often associated with aggression, competition, and risk-taking, those who readily detect androstenone in those around them might be more likely to seek comfort and protection in the arms of the secure, traditional social order that conservatives often hold out as the end goal of their policy stances. Thus, heightened sensitivity to odors such as androstenone may be consistent with favorable attitudes toward decisive leaders, protection from both in-group rulebreakers and out-group invasions, and a desire to promote traditional rather than avantgarde lifestyles…”
“…a strong positively-signed relationship appears between intensity of androstenone detection and ―conservative political orientations. Individuals espousing ―liberal political views (in the American sense of the term) tend to be less sensitive to the odor of
“To the extent androstenone is the odor of aggression and possibly social threat, people more sensitive to it could be more likely to have the perception that the world is a dangerous place and therefore to support special efforts to protect the social order…”
“Certain individuals are sensitive to the odor of androstenone and they also tend to be the people who are eager to squelch threats to the social order…”
Erik G. Helzer and David A. Pizarro stated the following in their study “Dirty Liberals! Reminders of Physical Cleanliness Influence Moral and Political Attitudes,” published by the journal Psychological Science on March 18, 2011.
“Many moral codes place a special emphasis on bodily purity, and manipulations that directly target bodily purity have been shown to influence a variety of moral judgments. Across two studies, we demonstrated that reminders of physical purity influence specific moral judgments regarding behaviors in the sexual domain as well as broad political attitudes. In Study 1, individuals in a public setting who were given a reminder of physical cleansing reported being more politically conservative than did individuals who were not given such a reminder. In Study 2, individuals reminded of physical cleansing in the laboratory demonstrated harsher moral judgments toward violations of sexual purity and were more likely to report being politically conservative than control participants. Together, these experiments provide further evidence of a deep link between physical purity and moral judgment, and they offer preliminary evidence that manipulations of physical purity can influence general (and putatively stable) political attitudes.”
Natalie J. Shooka and Russell H. Faziob stated the following in their research article “Political ideology, exploration of novel stimuli, and attitude formation,” published by Journal of Experimental Social Psychology on April 3, 2009.
“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 and discover the associated valence. 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. Mediational analyses revealed that the differences in learning were due to the extent of exploratory behavior during the game. Relative to liberals, politically conservative individuals pursued a more avoidant strategy to the game, which led to their development of a more pronounced valence asymmetry in learning and attitude formation…”
“The ﬁndings from this study highlight some of the broader correlates of political ideology. Conservatives’ intolerance of the unfamiliar, perceptions of the world as dangerous, and fear of loss were reﬂected in the cautious strategy adopted when playing BeanFest and learning about the novel objects. Liberals demonstrated more openness to new experiences by exploring the new bean world to a greater extent. These different approaches to interacting with one’s environment led to differences in attitude formation and participants’ perceptions of the bean world.”
“…this study provides clear evidence for the existence of relations among political ideology, exploratory behavior, and attitude formation…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.”
Dana R. Carney, John T. Jost, Samuel D. Gosling, and Jeff Potter, stated the following in their study “The Secret Lives of Liberals and Conservatives: Personality Profiles, Interaction Styles, and the Things They Leave Behind," published in the journal International Society of Political Psychology on October 23, 2008.
“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”