"First there was the "Me Generation" then "Generation Me." Now we have empirical evidence that we live in what will become known as the "Asshole Age" otherwise known as the Twitter Era..." — Personality Psychologist Brent Roberts on twitter

“Our movement is about replacing a failed and corrupt political establishment with a new government controlled by you, the American people. ... The political establishment, that is trying to stop us, is the same group responsible for our disastrous trade deals, massive illegal immigration, and economic and foreign policies that have bled our country dry... The only thing that can stop this corrupt machine is you." — Donald Trump's Argument For America

There are many divides in the world right now. But there's one divide, deeply embedded into the core of human nature, that helps explain many other divides. What I'm referring to is a source of human personality variation that is built right into our DNA: antagonism. By really zooming in on this trait, and understanding how antagonism interacts with environmental conditioning and messaging, we can gain a greater understanding of one of the most prominent divides in the world today: populism.

First, let's dive in to the latest science of antagonism.

The Science of Antagonism

The antagonism-agreeableness dimension of personality is one of the five main dimensions of personality. Like the other major dimensions of personality, this trait is normally distributed in the population. The more two people differ on this fundamental dimension, the more incomprehensible the other person's behavior may seem, especially when it comes to adhering to social norms and altruistic behavior.

Agreeableness (the opposite pole of antagonism) consists of two main aspects: politeness and compassion. Politeness reflects the tendency to conform to social norms and refrain from belligerence and the exploitation of others, whereas compassion reflects the tendency to care about others emotionally. People who score high in politeness are preoccupied with fairness whereas those who score high in compassion are more preoccupied with helping others, especially those in need.

On the other end of the pole, people with low levels of politeness (antagonistic people) tend to score high on measures of aggression, whereas those with low levels of compassion tend to score poorly on measures of empathy. While politeness and compassion can come apart—e.g., a person can score high in compassion but low in politeness—politeness and compassion are strongly correlated in the general population and both aspects together comprise the overall personality domain of agreeableness.

Like all other personality variation, differences on the agreeableness-antagonism dimension are reflected in the brain. Neurologically, those who score high on agreeableness tend to show greater activation of the default mode brain network, which is associated with the ability to simulate the mental states of others and the higher-level integration of different types of information necessary for both understanding and sharing the emotional experiences of others. Agreeableness is also associated with the capacity for emotion regulation, particularly the suppression of aggressive impulses and other socially disruptive emotions. From a neurochemistry perspective, agreeableness involves the neurotransmitters testosterone (related to the inclination away from politeness and toward antagonism) and oxytocin (related to the tendency for compassion and in-group social bonding).

The antagonism-agreeableness dimension has a lot of predictive value in the real world (not just in the scientific laboratory). Antagonistic people are more likely to respond aggressively and retaliate when treated unfairly by others (although they tend to care much less about whether others are treated unfairly). At work, antagonistic people perform better than highly agreeable people after receiving an angry speech from their manager (it fires them up), whereas highly agreeable people tend to improve their performance after their managers express happiness for their performance.

There are also deep implications of this personality dimension for politics. Politicians who are more antagonistic get more media attention and are more often elected than more agreeable politicians. In the general population, antagonistic people are more likely to distrust politics in general, to believe in conspiracy theories, and to support secessionist movements.

Antagonism isn't absolutely good or bad. Daniel Nettle speculated that all personality traits evolved to have trade-offs, and that's why variation exists in personality. From an evolutionary perspective, agreeableness has both benefits (attention to mental states of others; harmonious interpersonal relationships, valued coalitional partnerships) as well as costs (subject to social cheating and exploitation; failure to maximize selfish advantage). Nevertheless, because of the existence of such wide variation in this trait, highly antagonistic leaders can arouse and influence wide swaths of people who score high in this trait through their rhetoric and messaging.

Antagonism and Resonance with Populism

There has been an increasing recognition in psychology that personality traits interact with messaging from leaders. "A crucial skill for politicians is... to speak the 'language of personality'... by identifying and conveying those individual characteristics that are most appealing at a certain time to a particular constituency," note Gian Caprara and Philip Zimbardo. They found that voters select politicians whose traits match their own personality.

Along similar lines, Patti Valkenburg and Jochen Peter introduced their Differential Susceptibility to Media Effects Model (DSMM), which argues that the rhetoric and framing of a message has more cognitive and emotional impact on people who share particular dispositions than with other people. For example, the message of hope might be more attractive to those who are more prone to experience positive affect and enthusiasm, while the message of change might be more attractive among those willing to take risks.

Perhaps the most important interaction in the world today, however, is that between antagonism and populism. The core feature of populism is an anti-establishment message and a focus on the central importance of the people. The anti-establishment message portrays the political elite as corrupt and evil, and disinterested in the interests of "the pure people." According to John Judis and Ruy Teixeira, the essential divide among populists is "the people versus the powerful."

In a recent series of studies, political communication professor Bert Bakker and his colleagues conducted the largest and most systematic investigation into the question: What happens when antagonistic citizens receive an anti-establishment message? They found strong support for the notion that the anti-establishment message of populists resonates the most with highly antagonistic people. This finding was confirmed in seven countries across three different continents. Antagonism predicted support for populists for both right-wing (Trump, UKIP, Danish People's Party, Party for Freedom, SVP) and left-wing (Podemos, Chavez) populists.

Using physiological measures, they were also able to establish the deeper emotional processes that underlie this link. Employing a measure of skin conductance (which captures activity of the sympathetic nervous system), the researchers found an increase in arousal in response to political messages that were congruent with a person's personality. In particular, antagonistic people found an anti-establishment message arousing, whereas highly agreeable people found a pro-establishment message arousing.

This is important because emotions play an important role in determining how political communication affects us. Those who are more aroused by a particular message will be more likely to remember it, and to seek the message again in the long term. These findings suggest that politicians can exert substantial influence over voters by providing a message that resonates emotionally with the personality of the voter.

They also looked at authoritarianism. Authoritarianism encapsulates a preference for social order, structure and obedience. Prior research has shown that high authoritarians express less tolerance towards out-group members and support populist parties with a right-wing host ideology. Consistent with this, Bakker and colleagues found that while authoritarianism did not predict an anti-establishment message, it did predict support for Trump and UKIP, as well as any candidate with a strong anti-immigration stance. These findings suggest a second route to populism, through the particular ideology associated with right-wing populism.

Implications of the Antagonism-Agreeableness Divide

There seems to be something different in the air these days. Depending on your perspective (and personality), things are either more "sinister" or they are more "revolutionary." But I think we can all agree that the political landscape and discourse has changed dramatically in only the past few years. There were always party divides, but there seems to be prominence of a different kind of divide, that between the people and politicians. As Dutch political scientist Cas Mudde notes, "today populist discourse has become mainstream in the politics of western democracies."

It's important to emphasize that populism is an ideology that transcends liberalism and conservatism. Research shows that both liberals and conservatives are agreeable, but they are agreeable in different ways: the politeness aspect of agreeableness is associated with a conservative outlook and more traditional moral values, whereas the compassion aspect of agreeableness is associated with liberalism and egalitarianism. Conservatism and liberalism can complement each other; society needs those in power who care deeply about the fairness of everyone and the stability of society as well as those who are more exclusively concerned with the suffering of those in need.

It's also important to recognize that populism alone isn't necessarily dangerous. A healthy democracy will include those who challenge the government, and are critical of those in power. What is particularly problematic is when a highly antagonistic leader uses rhetoric that arouses the emotions of other antagonistic people and rallies them to support a particular host ideology that is pernicious. This can lead to a situation in which a high proportion of people in power are those who lack empathy, perspective-taking, and the self-control necessary to put the brakes on aggressive and disruptive impulses.

Of course, not all people who support populism are antagonistic people. There are a number of reasons why people support populists. The sociologist Arlie Russell Hochschild has done a tremendous job trying to understand what many Trump voters were thinking when they cast their ballots. The reasons include "lives ripped apart by stagnant wages, a loss of home, an elusive American dream, and political choices and views that make sense in the context of their lives."

Nevertheless, there is a growing prominence of antagonistic people on social media, YouTube, and alternative media outlets who believe they have better answers than the government "elite," and are empowered and aroused by Trump's populism messaging to have more influence than ever before. Rather than socioeconomic factors being the most prominent explanation for the appeal of populism (Bakker and colleagues actually controlled for socioeconomic status in their studies), a critical reason why people have become more receptive to populism is that people have become better educated and more free to speak their views in public. In fact, the appeal of populism is due, in part, to the increased egalitarianism of the 1960s, a consequence being that citizens today expect more from politicians, and feel more competent to judge their actions.

On the whole, this is a good thing. However, as Cas Mudde points out, more and more citizens think they have a good understanding of what politicians do, and think they can do it better, while at the same time, less people actually want to do it better by actively participating in various aspects of political life. Political theorist Robert Dahl put it well when he wrote, "Nearly a half-century of surveys provides overwhelming evidence that citizens do not put much value on actually participating themselves in political life."

Interestingly enough, populist supporters don't actually want to be led by the "common person"; rather, they want their own values and wishes to be enacted by a "great" leader. Mudde has found that most populist leaders are actually "outsider-elites"; they are highly connected to the elites, but they are not part of the elites. Supporters of populism simply don't want to be governed by an "alien" elite, whose policies do not directly satisfy their own wishes and concerns.

This research is important to keep in mind, as it looks like the use of populist rhetoric in the service of enacting more radical policies is not going away anytime soon. As Mudde observes, due to a number of factors, "populism will be a more regular feature of future democratic politics, erupting whenever significant sections of 'the silent majority' feels that 'the elite' no longer represents them."

Understanding differences in personality may not be the only factor involved in understanding the appeal of populism, but for the sake of the country and the world, it's an important one to consider.