It’s the reminiscence bump.

If you ask someone over the age of thirty to tell you their life story, they’ll over-emphasize some portions and under-emphasize others. Most likely they’ll recall incidents in their late teens and early twenties much more vividly than other periods of their lives. What happens in our thirties stays in our thirties. What happens in our formative years stays with us forever.

It’s known as the reminiscence bump and social scientists have been researching it since the early 1980s. Activities and events that occur in late adolescence and early adulthood leave an indelible mark on our memories. As Katy Waldman puts it, …”there is something deeply, weirdly meaningful about this period.”

Nobody knows quite why the reminiscence bump occurs. Dan McAdams, writing in the Review of General Psychology, associates it with the formation of identity. As we enter adolescence, many different identities are available to us. We could become nerds. Or athletes. Or scholars. Or criminals (especially those with low heart rates). As McAdams points out, William James called this the “one-in-many-selves paradox”.

Yet we generally emerge from adolescence with one more-or-less integrated identity. We want that identity to be coherent. Indeed, there are multiple types of coherent, including biographical coherence, causal coherence, thematic coherence, and temporal coherence. McAdams surmises that integrating multiple potential stories into one coherent identity is a formative life experience that creates long lasting memories.

The articles I’ve read focus on what causes the reminiscence bump. I’m also interested in what the reminiscence bump causes. We believe that the bump is universal; we all have it. Does the fact that we remember our formative years better than other years affect our behavior in later life?

I’ve written previously about the availability bias. As Daniel Kahneman has pointed out, humans are not naturally good at statistics. We have difficulty answering questions dealing with probability. So we substitute a simpler question and answer it.

For instance, let’s say someone asks us, “How likely is it that someone will burglarize your house while you’re away for the weekend?” We have no idea what the probabilities are or even how to calculate them. So we answer a simpler question: “How easy is it for me to remember stories of friends’ houses being burglarized?” If it’s easy to remember such stories, we estimate that the probability is high. If it’s difficult, we estimate that the probability is low. (This is sometimes known as the vividness bias – vivid events are easy to recall from memory).

What events are easy for us to recall from our life histories? Compared to all other events, the reminiscence bump suggests that events from adolescence and early adulthood are easiest to recall. The availability bias suggests that we will overestimate the probability that similar events will happen in the future. We can recall them easily. Therefore, we assume they’re highly probable to recur.

Now, consider the adolescent brain. According to the National Institute of Mental Health, it’s “…still under construction.” We tend to engage in riskier behaviors in our teenage years because our executive function is not fully developed. As most of us can well remember, we do stupid things.

What do we disproportionately remember about our lives? The risky and thoughtless behaviors of our formative years. If the availability bias is correct, we will overestimate the probability that these same behaviors will occur again, perhaps in our children. Could this be the root cause of the helicopter parenting that we seem so worried about today? It’s a complicated question but it’s certainly worth a good research project.