Bryan Caplan  

If the Mind Is a Muscle

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George Selgin on "The Bernank"... Mingardi on Hayek...
People often compare education to exercise.  If exercise builds physical muscles, then education builds "mental muscles."  If you take the analogy seriously, however, then you'd expect education to share both the virtues and the limitations of exercise.  Most obviously: The benefits of exercise are fleeting.  If you stop exercising, the payoff quickly evaporates.

I know this from bitter experience.  I was in weight-lifting class throughout high school.  The weights worked: After a few months, I had bigger muscles.  But after three months of summer vacation, my gains disappeared.  I was back where I started: scrawny.  Exercise physiologists call this detraining.  As usual, there's a big academic literature on it.

Here's a simple example.  Researchers ran a weight-training experiment with 20 kids: 11 subjects, 9 controls.  The training lasted 8 weeks, followed by 8 weeks of detraining.  Results:

detraining.jpg
The solid circles show the experimental subjects; the empty circles the controls.

Even more depressing, as my own weight-training taught me, is that within a few months you asymptote to your maximum ability.  Smaller progress hurts more and more.  And there're never more than a few months between giving up and going back to normal.

That's why, now that I'm older and wiser, I only do exercise I enjoy.  A life of suffering to slightly exceed my natural state isn't worth it.


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COMMENTS (17 to date)
Clay writes:

The study is mostly intuitive -- eight weeks of strength training aren't going to give you lasting strength benefits. However, a lifetime of routine exercise vs. a lifetime of inactivity absolutely will give you major health benefits. There are dozens of studies that lead to this conclusion.

Dominik writes:

If you ever used Spaced Repetition software, you know that not forgetting things is really hard work. I don't think many people notice that they forget almost everything they learn quickly afterwards. Look at the figures in here - they are remarkably similar to how muscle training works: http://www.gwern.net/Spaced%20repetition

nazgulnarsil writes:

"within a few months you asymptote to your maximum ability."

this is incorrect, within a couple months you run out of what are known as "newbie gains" in the lifting community. newbie gains go away quickly because you aren't training muscles, you're just training your CNS to use the muscle you already have.

actual LBM gains take a long long time to go away. The average adult male loses about 1lb of LBM per year.

sig writes:

"education" is not mental execise, any more than sitting in a chair is physical execise...

chess, suduku, & video games would be more apropos

Joseph K writes:

And I suspect that just like strength training, brain training is targeted. Certain exercises only strengthen certain muscles, and certain type of learning and brain exercises only target certain mental skills. Eg. if you don't practice your writing, or math skills, or logical reasoning, or recollection, etc, you'll lose in those areas.

blink writes:

@nazgulnarsil: What you say makes sense and sounds hopeful. Can you point to some further evidence or research on the subject?

Jess Riedel writes:

I second blink's request for cites from nazgulnarsil. (FYI, "LBM" stands for lean body mass, which is a rough measure of muscle.) The studies cited here say that healthy young adults lose about 1 pound per month (rather than per year) if confined to bed due to hospitalization. It's possible that LBM gains due to strength training decay more slowly when training is ceased (while maintaining a non-bedridden but sedentary lifestyle) than normal muscle decays due to bed-rest, but I'm skeptical it's 12 times slower.

Joe Cushing writes:

I have been through many cycles of weight training over the last 20 years. I can say that it is easy to gain and loose strength to a point (newbie gains) but it is hard to push past that. It takes a great deal of patience to build actual new muscle tissue. A person can gain about 1.5 pounds of lean muscle in a week. I don't know how fast one looses it. I can say that I tend to eat more and am heavier when lifting than not but to get more than 10 or so pounds above my average weight is not easy. I notice that my muscles get harder and harder but not much bigger, despite many years of working in the "bulk building" rep range. That makes sense given that I only gain a small amount of weight. It takes me about 3 months of lifting to reach peak strength. I'm there now. Pushing beyond is more of a mental challenge than a physical one.

zur writes:

I had a P.E. in HS teacher that told me he wants to train us students to be fit at that time and not to depend on the idea that we would continue to exercise in collage. But clearly he believed that exercise should be a daily thing. Also I discovered there are two ages when the basic metabolism of the body changes--about 40 and then again at 55.
And I think the same applies the the mind.

Glen S. McGhee writes:

The comparison is not particularly appropriate. While weight training, in and of itself, is beneficial to ones health, no such universal argument can be made for learning -- especially for learning that undermines the commonweal, such as chicken thievery.

What would make this discussion more meaningful is context.

Tracy W writes:

I am doubtful about this. When I first took up running I couldn't run 100 meters at once. Eventually I ran a half-marathon. The next year I got pregnant, and gave up running and any other rigorous exercise as I was very tired, then after the birth the physio advised me not to do any jarring exercise for 3 months. And I didn't do any swimming. When I started jogging again, while I wasn't as fit as I was, I could run far more than 100 meters comfortably.

Mike W writes:

The academic's version of kicking sand...a "study".

Finch writes:

Regarding the requests for citations, the exercise literature is just terrible. There basically aren't American citations for the effects of long-term exercise programs. There may be Russian cites, but they are corrupted by drug effects. Additionally, the American literature has a severe "exercise = light cardio" bias.

Most everything is a three-month study using either untrained college students or untrained elderly people, usually women because of the osteoporosis issue.

That said, anyone who trains seriously will describe what nazgulnarsil said: about three months of rapid gains and a lifetime slow progress from there. Anything works for the first three months, at least to some degree - ride a bicycle and your bench-press will go up. After that you have to start thinking and listening to coaches.

Finch writes:

For what it's worth, if you want to look and feel fit, weight training is the most time-efficient way to do it. Start with this book:

http://www.amazon.com/Starting-Strength-3rd-Mark-Rippetoe/dp/0982522738

If you want positive health effects, you probably need to add some cardio, although you probably want to avoid running (for injury reasons) and bicycling (for death reasons). And if you're not careful you'll wind up skinny, which is a bad look on guys and is associated with higher death rates. Athletic and "overweight" by BMI is where you want to be.

Xerographica writes:

I was the master fitness instructor for my Army unit...and then did some personal training while in college. Here are a few thoughts on the subject...

One fascinating concept is the idea of muscle memory. That means that even if you take a long break from working out...when you start working out again it takes a lot less time for your body to recapture the gains you lost.

A huge mistake people often make is to underestimate the importance of recovery. Allowing your muscles to rebuild themselves is just as important as tearing your muscles down. Basically...you want to work out hard enough to get sore...but then wait for the soreness to go away before you tear the muscles down again. Your body will addapt to your routine...and once that happens you need to change your routine to force your body to continue to adapt.

Let's see...all those infomercials with people getting ripped abs from using ab abber 2000 are ridiculous. Strength training helps build your muscles...but even the most developed muscles wont be visible if they are covered by a layer of fat. Cardiovascular training is what you need to remove the layer of fat in order to actually see the muscles.

Generally 40+ or so minutes of fairly low intensity cardio is what is needed to tap into your fat reserves. You should be able to just barely talk...but it's too low intensity if you can sing during your workout.

Another common error is people's perceptions of carbs. Carbs are your body's primary source of energy and you need energy if you're going to have a productive workout session. Generally there's nothing wrong with carbs...it's the things that people add to carbs that are the problem. Just like salads...salads are great until you start adding cheese...and bacon bits...and smothering the entire thing in ranch dressing.

If you're trying to lose weight...don't focus on your weight...focus on your percentage of body fat instead. This means it's really important to have healthy snacks readily available. If you let yourself get too hungry then your survival instinct kicks in and you start craving fat. I think this is leftover from our caveman days.

Most importantly, as you mentioned, is to find something that you enjoy doing. Partial knowledge for the win.

ladderff writes:

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Joe Cushing writes:

Carbs are only the body's primary source of energy if you don't get enough fat in your diet. Any northern person before farming didn't eat many carbs in winter. Before farming, no people at grain and very few if any ate potatoes. Carbs came from leaves, stems, and roots of plants. There were no supper concentrated sources of carbs that people eat today. Your brain needs about 30 grams of carbs a day. Most or all of that can be synthesized from fat. on a final note: sprinters tend to have much more lean muscle mass than marathon runners who might practice by doing 40 min of cardio. Anyone can tell this with a google image search of "track sprinters" and "marathon runners"

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