01/14/2011 09:48 am ET Updated Nov 17, 2011

Nostalgic for High School? Rethinking the 'Reminiscence Bump'

Some years ago, I found myself sitting out a blinding snow storm in a diner on a rural Maryland highway. It was bitterly cold outside, so I ordered soup and coffee and sat on a stool at the counter. I was the only customer for more than an hour, so I struck up a conversation with the fellow working there.

He was in his early 40s, I'd guess. He was friendly and did most of the talking, telling me about his high school days. His school was just a couple miles down the road. He had been an All-State linebacker on his championship team, and ran track as well. He had been popular and had lots of rich and entertaining stories about his escapades with his buddies and various girls, most of whom had left the area. He got married right after graduating, took some business courses at the community college, and now he owned this diner and was fairly successful. Still, the best years of his life were behind him.

I remember being saddened by his life story. Here was a man at middle age, still looking back nostalgically at his time as a boy. Had nothing else happened in the intervening years to eclipse his youthful fame and popularity? Was it all downhill from these peak experiences of high school?

It turns out he's not alone in his vivid recollections of young adulthood. For others, it may be their college years, or even a little later. Most middle-aged adults, though, men and women, have a similar "reminiscence bump" when they look back on their past. We all have more -- and more vivid -- memories of young adulthood than we do of any other time of life, no matter what personal and professional ups and downs we have along the way.

Why would that be? This memory phenomenon is so common and robust that psychological scientists believe it is more than just nostalgia. Indeed, the prevailing wisdom is that the reminiscence bump has biological and cognitive roots, reflecting the basic workings of autobiographical memory. According to this theory, our power to encode lasting memories is strongest at this stage of life, peaking before a steady decline into middle age and beyond.

However, new research is challenging this widely accepted view. Two Danish scientists, Annette Bohn and Dorthe Berntsen of Aarhus University, were unconvinced that the reminiscence bump is simply a consequence of better memory storage and maintenance. An alternative explanation is that the phenomenon is cultural, reflecting widely embraced life scripts -- shared expectations about the order and timing of life events. According to this view, the period of young adulthood is so important in the way we generally think of life's journey that it also shapes the way we think of, and recall, our personal lives.

Bohn and Berntsen tested this idea in a clever way -- by having children imagine the futures that lay ahead of them. It turns out that looking back on the past and imagining the future are very similar in their neural and cognitive underpinnings. Imagining the future, however, obviously has nothing to do with encoded memories. Therefore, if kids' imagined futures also show a significant bump in young adulthood, that evidence would favor cultural scripts, rather than memory, as an explanation of the phenomenon.

To test this, the scientists asked a large group of school children aged 10-14 to write their future life stories. They were not instructed about the kinds of events they should include; they were merely told to imagine the life ahead of them. When they were done, two independent readers analyzed each of the life stories, categorizing and dating every event, including both transitional events like marriage and incidental events like a memorable dinner.

The results were clear. As reported by Psychological Science, the majority of events that the children imagined were transitional life events clustered in young adulthood: buying a home, getting married, and so forth. There was also a bump, though a smaller one, in incidental life events, probably because the kids were embellishing the major events provided by the script. For example, kids often imagined getting a dog, but this was almost always linked to buying a home. In other words, the kids were using their broad cultural expectations as a "narrative scaffold" for a more detailed imagining of the future.

The scientists wanted to clarify these initial findings, so they ran a second and different kind of experiment. This time they gave the kids word cues (e.g. book, chair, telephone) and asked them to respond to the cues by imagining future events in their lives. They were also asked to date the events. Importantly, the imagined events sparked by these cues were mostly incidental events, not major life transitions, and they showed no bump in early adulthood. These events were imagined without activating the cultural script, so the bump disappeared. But sometimes these words did trigger thoughts of important life events. When this occurred, the events again clustered in young adulthood.

It appears that we all live by the same overarching script. Young kids use life's script as an outline for what to expect, and when. It gives the future some certainty and structure. The man I spoke with in the diner was using the same basic script as a guide for selecting which of many past events to include in his autobiography -- the life story he tells himself, and others passing through.