“If you’re not a liberal when you’re 20, you have no heart. If you’re not a conservative by the time you’re 30, you have no brain.” Variations of this saying have been attributed to Benjamin Disraeli, Otto von Bismarck, George Bernard Shaw, Woodrow Wilson, Theodore Roosevelt, Aristide Briand, and Winston Churchill. The thought first came, in fact, from a French statesman, François Guizot (1787–1874). Regardless of its origin, the adage raises a fascinating question: Do the young really lean left because of passions and idealism? And as people age, do they incline toward the right because they become more realistic or cynical?
For the past 10 years, I’ve studied political divisions through the lenses of evolutionary anthropology, genetics, and neuroscience. Research reveals that during their 20s people around the world experience significant shifts in the traits biologists use to describe the human personality. Specifically, “openness” declines and “conscientiousness” increases. Higher openness is associated with intellectual curiosity, a preference for variety, and voting for the left; higher conscientiousness, characterized by self-discipline and dutifulness, predicts support for more conservative politics.
This rightward shift in political personality is fairly universal, and so is the timing. A 2004 study by psychologists Robert McCrae and Jüri Allik in the Journal of Cross Cultural Psychology of 36 cultures across Africa, Europe, and Asia discovered that openness and conscientiousness differ between 18- to 22-year-olds and older adults. If an individual’s political personality hasn’t changed by the time of his or her 30th birthday, however, it’s not likely to differ all that much at 40, 50, or 60. This isn’t to say that all teenagers are liberal and all older people are conservative. In any age group, people are distributed along the left-right spectrum on a bell curve. The entire curve, however, moves somewhat to the right during the mid-20s.
A common explanation for this personality change in young adulthood was voiced during the politically turbulent 1960s in the U.S. At the time, the young leftist counterculture claimed that its ideological enemies could be found on the far side of Guizot’s magic number, 30. This belief implied that people older than that became more conservative because they were more likely to own a house, to earn a higher salary, and to have too much at stake to back a revolutionary call to destroy the existing order.
Contrary to popular belief, paying taxes, accumulating wealth, and being in the 1 percent or the 99 percent are extremely poor predictors of left-right political orientation. According to American National Election Studies, an academically run survey project, the correlation between family income and party identification for U.S. voters in the 2012 presidential election was a mere 0.13. This weak statistical relationship is typical of past elections.
There is one life event, though, that greatly accelerates a person’s shift to the right, and it often occurs in the 30s: parenthood. Its political impact is easy to see among a cohort of Canadian college students studied by psychologist Robert Altemeyer. Their scores on an ideology test at age 22 grew more conservative by an average of 5.4 percent when they were retested at 30. But among those 30-year-olds who’d had children, conservatism increased by 9.4 percent.
Why did having kids push people to the right? Parents stay on the lookout for possible sources of danger that nonparents can ignore. This shift in perception is so strong it creates an illusory sense of risk; new parents tend to believe that crime rates have increased since they had children even when actual crime has dropped dramatically. Because “dangerous world” thinking is associated with political conservatism, parenthood pushes people to the right, and more so when they have daughters.
Experts on personality, such as McCrae, a psychologist at the National Institute of Aging, say people’s personalities may also be hard-wired to shift over time. As we age, changes in gene expression may subtly alter openness, conscientiousness, and other traits. These traits and the personality shifts that unfold between late adolescence and early adulthood are moderately heritable between generations.
To understand why both nature and the environment tug at our personalities at certain times, we must trace these subtle changes in our personality to activity in the brain. Neuroscientists once assumed that the brain, along with the rest of the body, finishes dramatic development after puberty. But we now know that it doesn’t reach full maturity until at least age 25. Consider the prefrontal cortex, which lies directly behind the forehead. It’s responsible for regulating emotions, controlling impulses, and making complex cost-benefit judgments that weigh immediate incentives against future consequences. Unlike most regions of the brain, the prefrontal cortex continues to grow, and its cautionary functions go on developing well into the mid-20s.
Much earlier, in adolescence, a part of the brain called the limbic system, which plays a central role in sexual arousal and pleasure, kicks into action, stimulating thrill-seeking and risk-taking. Actuaries who work for car insurance companies have long deemed people younger than 25 risky. Why would nature permit this tempestuous gap between the flaring up of teenage passions and the onset of mental maturity 10 years later? These personality changes are probably evolutionary adaptations to different phases of the life cycle. High levels of openness encourage the young to wander the world and find a mate. Conscientiousness is crucial when raising a family.
Political pollsters are well aware of these life cycle personality changes, which is why they pay so much attention to age. When youth turn out to vote in higher numbers, as they do in presidential elections, analysts can stratify their samples to look for trends by age brackets that correspond roughly to before and after the brain developments that happen in the mid-20s: That is, they analyze the 18- to 24-year-old group separately from the 25- to 29-year-old group. In midterm elections, when the youth vote is underrepresented, pollsters often lump them all into one demographic group, 18 to 29.
In this era of big data, political pros of course have other tools at their disposal that make analysis of these large groups less relevant. As Chief Executive Officer Jim Walsh of the political ad network DSPolitical points out, it’s now easy to microtarget individuals of any age and according to dozens of other demographic and consumer categories. Nevertheless, public opinion experts still keep tabs on age groups to study their impressionability to the changing flow of history, culture, and economic cycles. In some cases, current events trump life cycle stages, altering the collective attitudes of a cohort in surprising ways. In 1984, 18- to 24-year-olds voted for Ronald Reagan over Walter Mondale by a 22-percentage-point margin—the same margin as 50- to 64-year-olds. This youth vote may have been anomalously conservative, because Reagan had presided over a strong recovery from recession and Mondale was perceived to be a weak candidate. Young Republican voters in 1984 may also have been expressing their feeling of disconnect with the liberal social movements of the 1960s and 1970s.
Today’s young voter adheres more closely to the personality pattern shaped by evolution, though environmental variables such as the social media revolution have left a mark as well. As expected, millennials lean substantially to the left on most social issues, but slightly less so on economic issues. These “digital natives,” who grew up steeped in social media, have also been dubbed the Selfie Generation. And Selfie may be a more apt description: The age group is characterized by individualism across the board. According to the Pew Research Center, millennials are far less affiliated with traditional political, religious, and cultural institutions and less likely to be married than previous generations were. Some commentators have accused the Selfie Generation of having a sense of entitlement, interpreting their individualism as a kind of Facebook-induced narcissism. Other observers have argued that millennials measure higher in cynicism and singleness—and more often live with their parents—because they face worse economic prospects than did the previous two generations.
Whichever perspective one takes, our changing economic and technological environments have surely left an impression on millennials and molded their political behavior in various unforeseen ways. Still, like most 18- to 29-year-old cohorts, their vote is markedly more liberal than average. Despite generational idiosyncrasies, the universal stages of life do influence our political orientations, true to Guizot’s words. And like many other facets of our political nature, these life cycle shifts have deep evolutionary roots.