Here’s one of my theories that I really can’t justify. In fact, I’m not sure it’s even mathematically possible. But somehow it just seems true, based on personal observations. (Remember how I promised more half-baked posts? Yeah, this is one of those.)
I believe each individual has an “anchor age” at which his apparent age is the same as his chronological age. Prior to this age, he looks old for his age; afterward, he looks young for his age. I’m not saying that a person always looks like his anchor age, only that his physical age advances more slowly than calendar time, and the anchor age is the crossing point. Take someone whose anchor age is 25. At 22, he looks old for his age – maybe 23. At 28, he looks young for his age – maybe 27. So in a six-year time span (from 22 to 28), his apparent age has increased by only four years (from 23 to 27). Graphically, it looks something like this:
So how does the average 28-year-old look older than this particular 28-year-old? While his anchor age is less than 28, others’ anchor ages are greater. Our idea of what the typical 28-year-old looks like results from averaging both groups.
Put differently, my half-baked theory is that the aging process appears faster when viewed in cross-section (many individuals of different ages at a single point in time) than when viewed in time-series (a single individual viewed over a period of years).
Like I said, I’m not sure this is mathematically possible. The main difficulty is there’s an endpoint problem. On the young end of the age spectrum, most people should not yet have reached their anchor age, so the average-of-apparent-ages should be greater than the chronological age. On the old end of the age spectrum, most people should have surpassed their anchor age, so that the average-of-apparent-ages should less than the chronological age. Both of these are impossible, if our notion of what chronological age X looks like is the average-of-apparent-ages of people at age X.
But maybe my theory can be saved via some kind of misperception (like this one) or non-linearity in the physical aging function. Suggestions welcome.