When I was a graduate student I was on a bus boarded by a middle aged gentleman wearing a baseball cap that boldly announced: Middle age is when your broad mind and narrow waist begin to change places. Now that my waist (but hopefully not my mind) has grown to approximate this description, I thought I would invest the time to investigate where the quote originated. After a quick Google search, I learned that the quote was the inspiration of one E. Joseph Cossman. Turns out Mr. Cossman was “an American salesman and self-made millionaire, best known for selling shrunken heads and ant farms door-to-door “. Mr. Cossman was also envied for his tolerance for change and accepting the challenges that change imposes. I admire the quote not simply for its creativity and wit, but also because it paraphrases a belief that is quite prevalent in society: our ability to think, to learn new things, and to remember those new things dissipates over time. But is it true that you can’t teach an old dog new tricks? Is our cognitive ability a prisoner of time?
The definitive answer to that question, according to the latest scientific literature is: it depends. Some of us age according to the scenario alluded to above, but I am sure that all of us know of at least one or two folk in their 70s, 80s or 90s who are sharp as a 20 year old. So, what determines whether we will age “successfully” or whether we won’t?
When I first arrived at the Douglas research center in 1991 two of my colleagues, Michael Meaney and Remi Quirion, showed me some intriguing results they had obtained: the cognitive abilities of the rat, like the human, age at different rates. Remi and Michael allowed animals to age to about 24 months (which is roughly the equivalent of a 75-80 year old human) and then assessed their performance in a standard rodent test of memory, the Morris water maze.
Rats are great at spatial navigation, this explains why they can adapt so successfully to the complex maze that defines all modern urban sewer systems. If rats were people, they’d make great taxi drivers (« resist completing the analogy, and shame on those of you who don’t»). The fact that rats are also proficient (albeit reluctant) swimmers also helps getting around in the sewer. So, in the water maze test, a rat is placed into a swimming pool where there is a platform hidden underneath the water. The animals’task is to locate the platform as quickly as possible within a maximum specified time period (usually 60 or 120 seconds). The rat solves this puzzle by developing a “cognitive map” of the location of the platform relative to spatial cues distributed both in the pool and the room in which the pool is located. As you might imagine the first couple of times the animal is placed in the pool, it swims around randomly, exploring, and stumbles onto the platform more or less by accident. However, after as few a 3-4 trials, most young rats will locate the platform within 10 seconds. Older rats fall into three categories: impaired animals never learn the location of the platform, their search strategies remain random. A second category of rat is slightly impaired, this brand of old rat finds the platform, but it may take him about 30-40 seconds to do so. Finally, we have the “successful” agers, those animals that find the platform as quickly as young rats do.
Before proceeding, let me respond first to those of you thinking it is unfair to compare the performance of old and young animals due to possible movement problems or weight differences. Old rats (whether impaired or not) can swim just as well as young rats. The difference is that successful agers know where to swim to, impaired animals do not.
Remi and Michael were interested in seeing if they could identify any biological differences between the successful agers and the impaired rats. When they invited me to collaborate on this project, I tackled a different question: Is the problem you see in the impaired rat restricted to spatial learning and memory, or might it be more extensive? Maybe the rats just don’t like new challenges, and this might explain why they never learn. So, we did something very simple: we exposed impaired rats, successful agers, and young rats to a variety of new life experiences: we challenged them with new objects, new environments, even new (and tasty) foods.
What we found was that like the young animals, successful agers showed an initial (and appropriate) disinclination for novel stuff; this reluctance rapidly dissipated, however, and the animals completely engaged their new found toys and treats. Impaired animals, however, did not adapt or habituate; they avoided novelty like the plague. As the data accumulated, and I saw the pervasive pattern emerging, I couldn’t help but think that these animals are living their lives with a psychological “veil” around them, preventing the outside world from looking in, and impeding the inside world from fully engaging and accommodating the changes that define life.
But what accounts for this veil of impenetrability, what is its source? We’re not completely sure of the answer to this question; one thing we do know is that it is not likely the consequence of anxiety in the face of originality. Rather, it seems to stem from a simple disinterest in change. There may be comfort in the “status quo”, in routine, but too much of it imposes a significant psychological cost. Your mind shrinks, and that shrinkage may ultimately deprive you of the motivation to expose yourself to things that might bring you some joy.
The media bombard us with exhortations to remain physically active, and that is a good thing because physical exercise does attenuate the rate of growth in our midriffs. And narrow midriffs have been shown to help ward off a whole variety of physical ailments. Narrow waists are good things, but narrow minds are not. Your high-school teachers were actually paying you a complement they called you a “fat head”. Modern neuroscience has indicated to us that we should aspire to doing what it takes to maintain “fat heads” for as long as we can. Paradoxically, perhaps, the way to maintain a fat head is to exercise it, and the way to exercise your fat head is by maintaining an active interest in innovation, inventiveness and unfamiliarity.
If you haven’t already tried it, selling shrunken heads may not just make you rich, it may also protect your own head from atrophy.
17 Jun 2008