People most remember events from late adolescence and early adulthood, scientists say. (The Washington Post)

Our 20-somethings are having a moment. They’re inspiring self-help guides, television shows, Tumblrs-turned-handbooks, major newspaper and magazine think pieces on why they do what they do (or don’t do). The current crop of young adults are recession-squeezed, peculiarly savvy and adrift, connected and lonely, knowing and naive. But what is it with 20-somethings in general? And why are we so fixated on this no man’s land between childhood and stable adulthood?

A little-known but robust line of research shows that there really is something deeply, weirdly meaningful about this period. It plays an outsize role in how people structure their expectations, stories and memories. The basic finding is this: People remember more events from late adolescence and early adulthood than from any other stage of their lives. This phenomenon is called the reminiscence bump.

Although studies have shown that our memories have a particular affinity for events that happen during the third decade of life, researchers aren’t sure what causes us to drench those years with special import. Is it the intrinsic qualities of events that happen within that time frame, a consequence of the way our 20-year-old brains encode information, or a recall strategy that arbitrarily favors milestones from our salad days?

Autobiographical memories are not distributed equally across the life span. People tend to experience a period of childhood amnesia between birth and age 5, a reminiscence bump between 10 and 30 (with a particular concentration of memories in the early 20s), and a vivid period of recent memories that wanes back to the end of the reminiscence bump.

At first, researchers proposed that the reminiscence bump coincided with a phase of developing mental firepower. Young adults encoded more information about the world, the theory went, because they were using state-of-the-art biological equipment: relatively fresh and agile minds. As cognitive function declined with age, the flood of recorded memories would naturally slow to a trickle, though recent experiences would remain accessible.

Going deeper into the mechanisms of recall, though, scientists also noted that the brain transcribes novel experiences more readily than mundane ones. For instance, a 1988 study found that 93 percent of vivid life memories concern unique or first-time events. Might the reminiscence bump reflect the fact that late adolescence and early adulthood are suffused with “firsts” (first relationship, first time leaving home, first job, first marriage, first child)?

Joshua Foer, author of “Moonwalking With Einstein: The Art and Science of Remembering Everything,” allowed that the reminiscence bump seems to be related to “how adulthood is structured.” One’s 20s, he said, form “the period that’s the most varied and exciting; that’s when you’re hitchhiking across the country, going on lots of dates, having interesting encounters and learning about things for the first time. You’re going to remember your trip hiking across Peru more than the year you spent sitting in your office doing the same job you’d been doing for the past five years.”

Yet this doesn’t explain why only a small portion of the memories that constitute the reminiscence bump relate to novel experiences. A 2010 study by Annette Bohn and Dorthe Berntsen created a form of reminiscence bump in schoolchildren without asking them to remember a thing. They had a large group of students, age 10 to 14, write their life stories. Most of the future events the kids dreamed up clustered around young adulthood. If the reminiscence bump were merely an offshoot of how our brains store memories, the researchers argued, the children wouldn’t have also focused on their future 20s when projecting ahead.

Such findings lend credence to an alternate theory about the bump that’s known as the narrative perspective. This focuses not on the mechanics of memory but on its underlying motivational factors. It suggests that people organize remembered events in ways that help them understand who they are.

In 2002, Berntsen and David Rubin advanced a “life script” account of the reminiscence bump. They defined the life script as a culturally conditioned story line of events that make up a skeletal life course — and claimed that people often consult such a template when asked to remember their pasts. According to the researchers, the benchmark moments in life scripts have two relevant features: They’re usually happy — childbirth, one’s wedding day, etc. — and they occur with greater frequency during one’s 20s and late teens. (Why happy? Perhaps because joyful scenarios are more fun to rehearse and also help us regulate our moods. Or perhaps because we are reluctant, collectively, to acknowledge that our time on Earth will contain suffering as well as pleasure.)

So what about the recollections of events that don’t fall within the parameters of the life script, the sad or unexpected ones? Why do these memories sometimes return with such laser-cut sharpness? A survey of older Bangladeshi men and women taken in 2000 revealed two reminiscence bumps: one in the typical 10-30 age range and one between the ages of 35 and 55. The second bump was linked to a sorrow-tinged accident of history that the participants’ life scripts failed to predict: the Bangladesh Liberation War of 1971, in which many civilians were killed.

The strength of the wartime memories couldn’t be entirely explained by the fact that those years were dramatic and frightening. Something else made the survivors’ painful memories so persistent, and that something might shed light on the standard reminiscence bump in ways the life script couldn’t.

The Bangladeshi study set the stage for yet another explanation of our memory processes, one based on “self-defining episodes.” It could be that we favor recollections, whatever their emotional charge, that reinforce who we think we are. In this case, identity and memory are interfused: Our self-image hangs on the experiences we salvage from the past, and we select certain moments for safekeeping because of how they anchor our self-image. Maybe the fact that the Bangladeshi survey takers remembered a period of political strife so lucidly meant that they found it personally formative. Likewise, if we recall more experiences from young adulthood, perhaps that’s because our sense of self glimmers between those early milestones.

To test this theory, scientists from the University of Leeds, noting that developmental psychologists have isolated the second and third decades as times of identity formation, gathered a group of volunteers and tried to map the emergence of their self-perceptions. Participants were asked to complete 20 “I am” statements. (e.g., “I am quick-tempered”; “I am a mother”). Then they were instructed to pick three statements and come up with 10 memories that seemed relevant to each. Finally, the volunteers were told to pinpoint as best they could the ages at which their three personality traits surfaced.

If it’s true that we remember more assiduously during bursts of self-making — and that these self-making periods tend to span our late teens and early 20s — a few things should happen, the researchers reasoned. First, participants should frequently date the unfurling of their “I am” statements to young adulthood. Second, the memories they summoned to support each “I am” statement should cluster around the age at which they believed the “I am” statement started to apply.

That was exactly what happened. A majority of the memories associated with a particular self-image came from the same year that the self-image developed. It seemed clear that the more salient a past experience was to your identity, the more luminous it grew in your memory. And the median age at which all these traits and self-concepts were acquired was22.9 years.

In the pilot of the television show “Girls,” Lena Dunham’s Hannah Horvath delivers one of the 2012 fall TV season’s immortal lines. She can’t hang out with her parents, she explains exasperatedly, because “I have work, and then I have a dinner thing, and then I am busy — trying to become who I am.” Memory research supports this notion that our 20-something years are gardens of self-creation. No wonder the decade is so, well, memorable.

Scientists Judith Gluck and Susan Bluck have proposed that the convergence of three qualities can make an event indelible in our minds: It is joyous. It allows us to exert control. And we perceive it to be highly influential over the course of our lives. They add that all of these qualities fit into a narrative, identity-based account of the reminiscence bump, since we are eager to thread our autobiographies with positive experiences, to assert our agency and to array the flux of our being across scaffolds of cause and effect.

Foer, too, seems most persuaded by the identity-based approach to the reminiscence bump. “The fact is that in this period [one’s 20s], you are becoming the person you’re going to be,” he says. He describes a study in which researchers found that most movie adaptations and remakes occur exactly 20 years after the originals come out. Apparently, whatever touches people as young adults looms so large for the rest of their lives that when they reach the age at which their generation starts to create the culture — around 40 — books and screens fill up with the arcana of 20 years earlier. “So look out for a new Teenage Mutant Ninja Turtles film any day now,” Foer finished. Consider yourself warned.

This article was produced by the online magazine Slate.