Another Mysterious Mental Improvement

A month ago I posted this graph, which shows how long I needed to type the answer to simple arithmetic problems (7-5, 4*1, 9+0). I tested myself with about 40 problems once or twice per day. Because I’d been doing this for a long time, I no longer improved due to practice. Then, at the end of July 2010, I started improving again.

In September I moved from Berkeley to Beijing. I was worried that in Beijing my scores would get worse. Perhaps I couldn’t get good flaxseed oil or butter. Maybe I would suffer from the air pollution. Maybe I would eat contaminated food. But my scores got better in Beijing.

When I eventually noticed the improvement, I wondered what I was doing differently. Obviously my diet and my life were a lot different in Beijing than Berkeley. Was I eating more walnuts in Beijing? I stopped eating walnuts and my scores didn’t get worse. So it wasn’t walnuts. The most plausible differences I could think of were: 1. Less aerobic exercise in Beijing. 2. Less vitamins in Beijing. 3. Warmer in Beijing. I collected data that implied that shower temperature matters — and I can take warmer showers in Beijing than in Berkeley.

All of these proposed explanations implied that the crucial difference was Berkeley versus Beijing. But the improvement started in Berkeley— around the end of July. That was a problem. Recently I realized there was another possible explanation. In Berkeley I had had an amalgam mercury-containing filling replaced with a non-metallic filling. Not because I had symptoms of mercury poisoning, but because it seemed prudent.

I checked my records to see when I had the filling replaced. It was July 28 — right when the improvement started. To my shock, reduction in mercury exposure is now the most plausible explanation of the improvement. Two tests of this explanation are coming up: 1. When I return to Berkeley, will my reaction times go up? 2. When I have more amalgam fillings replaced, will my reaction times go down?

If it turns out that reduction in mercury exposure is the correct explanation, this will be important. I have an average number of fillings. I’d guess that half of Americans have as many amalgam fillings as I did. And — if the mercury explanation is correct — this arithmetic test is a sensitive measure of mercury poisoning. Over the last few years, before the filling was removed, I’d had six hair tests done, all from the same reputable lab. They showed that my mercury level was moderately high, perhaps 75th percentile. Not very worrisome.

I changed dentists because my old dentist made a terrible mistake: he put a gold filling next to an amalgam one. Putting one metal next to a different one is an elementary mistake. Contact of different metals creates an electric current (as Galvani discovered) and releases mercury. (So although I have a normal number of fillings perhaps I have more mercury exposure.) I stopped going to him for any dental work. The last time I went there for a cleaning, I was given a booklet (”we must give you this”) about the many sorts of dental materials — mercury amalgams plus several new ones. The purpose seems to be to tell people mercury amalgams aren’t dangerous (this was stressed) yet get them to choose other materials in the future — mercury amalgams are just one of several possible choices. The controversy about the safety of mercury amalgams is covered here. Sweden, Denmark, and Norway have banned mercury amalgams. The ban began 2008.

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12 Responses to Another Mysterious Mental Improvement

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  3. Matthew Cornell says:

    So a natural test is to measure mercury level now (you have results from before) and then again when you get another filling replaced.

  4. Gordon Freeman says:

    I plotted your data against monthly average temperature in Beijing and Berkeley.

    The plot thickens:

    • JDub says:

      Seth, temperature is a pretty big variable to leave out of the analysis. Surprised you didn’t consider it.

      • Seth Roberts says:

        Gordon and JDub, I did consider temperature. I found that shower temperature mattered, in the correct direction to explain the effect: warmer temperatures cause shorter reaction times. (Because in spite of what that graph shows, my Beijing apartment and showers are warmer than in Berkeley.) The problem with shower temperature or ambient temperature being the whole explanation is that it did not suddenly start getting warmer at the start of August. The temperatures plotted by Gordon show that August is usually cooler than July, not hotter. (I have not checked the temperature records for last August). Nor was I taking cold showers in Berkeley. However, if future results argue against a mercury explanation, the temperature explanation will become more plausible. One test will be when I return to Berkeley. That won’t change my tooth fillings. But it will change the temperature of the showers I take.

        • SVideo says:

          If only there were some kind of statistical test that you could use to rule these hypotheses in or out beyond a certain level of doubt…

  5. OldSchoolFan says:

    Seth, this post brought to mind the recent story about Jeremy Piven suffering mercury poisoning due to excessive sushi consumption. Would it be possible to “tune” your sushi intake to produce a significant (but small enough to be safe) increase in your mercury levels?

  6. OldSchoolFan says:

    To be clear, I’m suggesting sushi consumption as a means to increase your mercury levels to see what effect that has on the arithmetic test.

    • Seth Roberts says:

      I know that sushi contains mercury. I know that mercury in doses you can get from sushi harms the brain. A San Francisco doctor showed that. So the results wouldn’t be interesting. I avoid sushi partly because of the mercury. To me, the value of my arithmetic test is that it is able to find out things I never thought of. It had not occurred to me that shower temperature would affect brain speed, that butter would improve brain speed, and so on. It had not occurred to me that removal of a mercury-containing filling would noticeably improve brain speed. The results of a sushi “challenge” would be interesting to someone who wants to eat sushi but is afraid of the mercury — but I’m not one of those people.

      • SVideo says:

        I believe OldSchoolFan’s point is that eating sushi would be positive control for the effect of your mercury filling on your arithmetic speed. Alternatively, you could also run this control by keeping a (detached) filling in your mouth for a couple of weeks. It would be important not to change other variables during this trial, especially walnuts.

        • Seth Roberts says:

          SVideo, it is extremely hard to know how much mercury is in this or that piece of sushi. So it would be extremely hard to interpret a null result (no effect of mercury on arithmetic speed) in the experiment you propose. If there were an effect, that would be interesting to people who eat sushi, but I’m not one of them.

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