This doesn’t have a lot to do with philosophy, but it’s a curious thing, so what the hell, I thought.
I’ve been having a mid-life crisis for about the last fifteen years. Obviously, chasing girls, oops, sorry, women, is a large part of the story, but I’ve also become pretty interested in the link between ageing and physical decline.
Anyway, I’ve just noticed that a new piece of research has been published in the BMJ, which shows that cognitive decline is already evident by the time people hit middle age. Basically, they looked at tests of memory, reasoning, vocabulary, etc., and found that
all cognitive scores, except vocabulary, declined in all five age categories (age 45-49, 50-54, 55-59, 60-64, and 65-70 at baseline), with evidence of faster decline in older people.
So that’s pretty depressing, but perhaps not all that surprising. I remember Norman Levitt once telling me something to that effect about the career path of mathematicians:
You do slow down. Not everybody, but there is a tendency to be really bright when you’re twenty-two, and then it becomes more of a slog as you get older. People’s really brilliant stuff tends to happen when they’re younger. There are exceptions, but you can look at people’s career paths and you find that whilst they might be brilliant at twenty-four this eases off as they get older. It comes with the territory.
But here’s the thing, and perhaps somebody who knows this field, might be able to shed some light on this matter. If you’re doing that sort of longitudinal study, how do you control for motivation? If I had ever taken an IQ test in my 20s, or perhaps even my 30s, I’d have been pretty keen to do well. But now, well I wouldn’t give a bugger. Even if I told myself I had to perform to the best of my ability, I’m pretty sure it’d be futile, because I just don’t care enough. Possibly I’m unusual in this respect, but I doubt it, and certainly it’s an open possibility that motivation will decline with age (which might have a physiological component, of course, but which might not generalize – in other words, it’s possible that if one was doing some task that one considered important, then motivation levels would stay high, with concomitant improvements in concentration, and thereby performance).
So that’s my question. How do you control for motivation in these sorts of longitudinal studies?