Life stages became more standardized in the late nineteenth century, as mandatory schooling spread, and legal thresholds of adulthood were set in the twentieth century. In 1971, the Twenty-sixth Amendment instituted eighteen as the voting age in America, and, in 1989, the U.N. Convention on the Rights of the Child promised protections for people under eighteen. Meanwhile, retirement ages and pensions set parameters for the beginning of old age. Arnett developed the category of “emerging adult” after many twentysomethings told him, in the nineteen-nineties, that they didn’t identify as adults—they felt “off time,” he told me. Arnett thought that age-based life stages seemed increasingly outdated, given that people were, on average, getting married later, leaving school later, finding jobs later. The novel stage of emerging adulthood reflected modern life. “Some people, when I proposed it, said, ‘You can’t just invent a new life stage,’ ” Arnett said. “There was this assumption that they’re universal and they’re fixed. I didn’t see them that way.”

Neither does Clare Mehta, a psychologist at Emmanuel College who works with Arnett, and who came up with the term established adulthood. Mehta argued that psychologists had neglected this busy period when they had consolidated adulthood into a monolith. She saw people between thirty and forty-five trying to balance careers, marriages, and children for the first time. Established adults hadn’t yet reached the apex of their careers; some had young children at home, and, for most in this life stage, neither major health issues nor menopause had typically set in.

Mehta’s research, which is ongoing, includes interviews with people my age. During a two-hour Zoom call, she asked about my life. I didn’t want to define my stage in terms of discrete events such as buying property or exchanging vows, although I had recently done both of those things; after all, I could imagine doing those same activities in my twenties, just in a very chaotic and non-adult sort of way. Other ways I’ve grown seemed more important. These days, I better understand and manage my emotions. My interactions with other people seem less mysterious to me; I’m more patient and empathetic. In my family, I’ve adopted a more live-and-let-live attitude. I’m proud of progress in my career, even if I am far from settled.

It turns out that other established adults feel the same way. In 2024, Megan Wright, a postdoctoral research fellow at the University of York, worked with several colleagues to assess how more than seventeen thousand people defined adulthood. Across a variety of ages and countries of origin, only a quarter cited marriage and having children. A similar fraction mentioned turning eighteen. But a majority of people said that taking responsibility for their actions, paying for living expenses, and having stable careers made them feel grownup. In another study of roughly seven hundred U.K. residents, most participants defined adulthood with psychological milestones, such as “accepting responsibility for the consequences of my actions.”

Historically, life stages have been aspirational—they’ve been defined by societal expectations—which also made them limiting. “There’s just something about them that’s too set in stone,” Dan McAdams, a psychologist at Northwestern who directs the Study of Lives Research Group, told me. “They’re élitist. They’re too prescriptive. Modern and postmodern life is too variegated. People follow so many different paths now.” What if you don’t want to get married and have children? What if you can’t afford to buy property? What if you aren’t a man?

In some ways, Arnett and Mehta’s newer stages of life are more reflective of these realities. Mehta said that one feature of established adulthood is deliberation over whether to have children; there are many good reasons that the answer might be no, including economics, preference, fertility challenges, and the demands of a person’s career. But it’s still easy to chafe against these categories. When Mehta’s husband was in his mid-forties, she asked him if he felt like an adult. No, he said, even though he owned a house and two cars and had started a company. Why not? “He said that he’d played pinball for eight hours the day before,” Mehta recalled. “Do adults play pinball?”

I related to the idea of established adults more than any other life stage. Even so, the divisions seemed arbitrary and subjective. I was surprised to find that Mehta and Arnett agreed; they know that stages don’t apply to every person. McAdams prefers to think of life as a story that we tell ourselves, with a protagonist, a plot, and a cast of characters.