The aptly-named, given the topic, Jennifer Senior writing for The Atlantic minds the gap between how old you are and how old you think you are, which I’ll be honest is not at all something I ever realized existed as a thing.

But “How old do you feel?” is an altogether different question from “How old are you in your head?” The most inspired paper I read about subjective age, from 2006, asked this of its 1,470 participants—in a Danish population (Denmark being the kind of place where studies like these would happen)—and what the two authors discovered is that adults over 40 perceive themselves to be, on average, about 20 percent younger than their actual age. “We ran this thing, and the data were gorgeous,” says David C. Rubin (75 in real life, 60 in his head), one of the paper’s authors and a psychology and neuroscience professor at Duke University. “It was just all these beautiful, smooth curves.”

The closest I’ve come to an awareness of my internal age not matching my external age is when in the early-90s I chose my first-ever internet handle based upon the sense that I was “five-plus years behind where I was supposed to be”. Even that, though, had more to do with the fact that my then-undiagnosed autism was holding me back from hitting normative milestones than with an internal sense of my age.

What I wondered while reading this article is whether or not I don’t seem to have a sense of how old I am in my head because of severely-deficient autobiographical memory. When I say I don’t have that sense, I mean that in both ways: I don’t really know what it’d feel like to be some specific inside my head any more than I know what it’d feel like to be some specific age outside my head.

If I don’t really have a definitive and lucid sense of experiencing my past, maybe that does something to your sense of time, and your sense of change—and I’d think that would have an impact on having a sense of how old you are in your head.

There’s also a throwaway reference in the piece to a “combined vigor-maturity index” and, honestly, I can’t imagine that I ever had a time when I felt both vigorous and mature.

Apparently, older people in their heads are younger, and younger people in their heads are older, so the story I told above would suggest that I’m pretty backwards on all of this. That might be why today, in my midlife, I mostly just consider myself more than half dead.