Month: February 2007

Science in Action: Omega-3 (results with new measures)

Seth RobertsLeave a comment

Yesterday I blogged about three new measures of mental function that I have recently started to use. Here are the first results.

1. Memory-scanning.

early memory-scanning results

Each point is a mean; the error bars show standard errors. I expected a within-session warm-up effect (Trial 1 slower than Trials 2-5) but there isn’t one so I use variation across the 5 trials (100 digits each) to get a standard error.

2. Digit span.
early digit-span results

The program increases the number of digits to remember by one when I’m right and decreases that number by one when I’m wrong. The test continues until there have been six reversals in direction of the number of digits (e.g., the sequence 5, 6, 7, 8, 7, 6, 7, 8, 9, 8 contains three reversals). Each pair of reversals is averaged to get an estimate of digit span; I use between-average variation to get a standard error.

Digit span slowly improves with practice, other researchers have found. The increase is slow, however — one digit for every two hours doing the task.

3. Speeded arithmetic.

early speeded-arithmetic results

The questions differ greatly in how long they take (7*9 much slower than 1+0) so I fit a model to remove obvious effects and use the variation of the residuals to get standard errors. I think these results are so erratic because I did the test in several different places and in some cases I corrected mistakes (which is very slow). Now I don’t correct mistakes.

Science in Action: Omega-3 (new measures)

Seth Roberts6 Comments

My balance measurements, such as this, this, and this, have come close to convincing me that flaxseed oil improves my balance. If a nutrient improves one part of my brain, it will probably improve other parts, too. So I’ve added three more measures of brain function to my daily tests:

1. Memory scanning. A paper-and-pen task. After studying three digits (e.g., “3 7 9″) for a few seconds, I go through a block of digits marking each one “in” (equal to 3, 7, or 9) or “out” (not equal) as fast as possible. Each test consists of 5 blocks of 100 digits. Duration: 5 minutes. Pluses: Similar to a well-studied task (Sternberg’s memory-scanning task). Minuses: Requires a little bit of equipment (sheet of digits).

2. Digit span. I see a series of digits on my laptop screen then try to remember them. The number of digits goes up and down depending on my accuracy. Duration: 4-6 minutes. Pluses: A well-studied task. Quite different than balance, memory scanning, and speeded arithmetic (below). No special equipment. Minuses: Little computation involved, unlike balance.

3. Speeded arithmetic. I do 100 simple arithmetic problems (e.g., 4 + 8, 3 * 5) as fast as possible. Duration: 2 minutes. Pluses: Tim Lundeen found an effect of fish oil on this task. No special equipment. Measures long-term memory retrieval, unlike other tasks. Intense — the 2 minutes are full of mental activity. Minuses: No obvious ones.

One of these may emerge as a better way to study the issue than balance measurements. The biggest problem with balance measurements is strong practice effects. The more often I measured, the better I became. (The area of my brain devoted to the task seemed to increase. The tiny balance platform seemed to grow.) Perhaps practice effects will be less of a problem with at least one of these tasks. Perhaps one of them will show clearer effects of flaxseed oil.

In a comment on an earlier post, someone suggested using chess as a measure. A fun test would be a good addition. Chess has two big problems: 1. Openings are time-consuming and quite different from the rest of the game. 2. If you take longer to make a move you can make a better move. So the amount of time allowed per move must be fixed. Which is less fun.

Self-Experimentation on TV

Seth RobertsLeave a comment

The BBC is now running a four-part series on medical self-experimentation called Medical Mavericks. The examples have almost nothing in common with what I do. Here are some differences between what might be called “classic” self-experimentation (e.g., Weinberger, Marshall) and “slow” self-experimentation (what I do).

1. Classic SE: Improves medicine. Slow SE: improves my life.

2. Classic SE: few if any numerical data. Slow SE: Lots of numbers.

3. Classic SE: self-experimenter starts with strong opinion. Slow SE: self-experimenter starts without strong opinon.

4. Classic SE: lasts hours or days. Slow SE: May last years.

5. Classic SE: Demonstrative. Slow SE: Exploratory.

Long live both types.

Pregnancy and Omega-3

Seth Roberts2 Comments

A new study has found that mothers who eat more fish (high in omega-3 fats) during pregnancy have smarter, better-behaved children. Many expected the opposite: They assumed more fish = more mercury = more damage. Here is a newspaper story about it.

The study, which appeared in The Lancet, has an odd title: “Maternal seafood consumption during pregnancy . . . ” — as if paternal seafood consumption during pregnancy could affect the fetus. It involved about 10,000 pregnant women. The seafood/better-brain correlation was seen with several measures, including IQ scores at age 8. The authors tested the explanation that low seafood consumption was simply a marker for an unhealthy diet by taking dietary quality into account in various ways; this had little effect on the results, the authors say.

Current Food and Drug Administration advice to limit seafood consumption during pregnancy may be harmful, the authors note.

Thanks to Timothy Beneke for the pointer.

Omega-3 and Freakonomics

Seth Roberts2 Comments

Steve Levitt, co-author of Freakonomics, has done me the great favor of bringing my omega-3 self-experimentation to a wider audience in this post. He thinks my results might be due to my expectations. I posted this comment:

Thanks, Steve, for writing about this. Here’s why I think the balance improvements I’ve noticed are unlikely to be due to expectations:

1. I first noticed the effect putting on my shoes the morning after I started taking flaxseed oil. I had been putting on my shoes standing up for two years; until that morning, I had always had trouble. Every morning. (I had expected it to get much easier — practice effect — but it didn’t.) The sudden improvement was a complete surprise. I had never heard of such an effect. I had hoped that flaxseed oil would improve my sleep.

2. The sudden improvement I saw when I switched from 2 tablespoons/day to 3 tablespoons/day was also a surprise, although I realize this may be harder to believe.

3. When I switched from flaxseed oil and walnut oil to sesame oil, I expected my balance to get worse. It did, but not when I expected. (It took 2 days to see a change; I expected to see it on the first day.)

Which is not to say I’m sure. If the effects I’ve seen are repeatable, I’ll test myself not knowing what oil I’ve ingested.

And forgot to sign my name. Oops.

My reading of the data (such as this) is that placebo effects sometimes exist but are vastly overrated — like many dangers.

Addendum: Stephen Dubner, Levitt’s co-author, blogged today that

nearly everything we’ve written about, either in the book or our journalism or the blog, has some element of people worrying too much about something

Science in Action: Omega-3 (sleep data, discussed)

Seth Roberts1 Comment

This is a discussion of the facts and ideas in my previous post. In summary, several observations, involving both me and others, suggest that a few tablespoons of oil (at least olive oil, sesame oil, and flaxseed oil) in the evening improve sleep.

I’m not yet sure of this conclusion, even for myself. But several things are already worth pointing out:

1. It took several facts to change my mind (I originally thought the sleep improvement was due to omega-3 fat and had nothing to do with when I ingested it) but it did happen. Strangely enough, it happened when I was studying something else: The effect of omega-3 on my balance. I switched the time I drank flaxseed oil from 10 pm to 10 am to see if this affected my balance. (I don’t yet know the answer.)

2. The conclusion that a few tablespoons of fat late in the evening improves sleep is remarkably isolated. I have never read anything similar in the scientific or self-help literature. Most of my self-experimental conclusions, however odd they may strike outsiders (such as my recommendation to skip breakfast), are supported by many mainstream scientific results. (The breakfast conclusion, for example, is supported by dozens of studies of anticipatory activity in animals.)

3. It’s a big effect — one more hour of sleep per night. No wonder most Shangri-La dieters noticed it.

4. The long-term records of my sleep, which I had kept for no particular reason, came in handy. They made it clear that something had recently caused me to sleep longer each night. Which implied that it couldn’t be fat per se that caused the improvement — I’d been drinking ELOO (extra-light olive oil) for the past two years. The term self-experimentation doesn’t obviously encompass keeping such long-term records; they are better suggested by the term self-observation or even numerical self-observation. But whatever the term, they don’t have an obvious correlate in more conventional science. Experiments with yourself as the subject are just conventional experiments writ small and personal, you could say. But there is no part of conventional science that tracks people closely year after year. It makes scientific sense; it would be a way of getting new ideas. You might track 100 people (say). When someone’s health markers got suddenly better or worse you would investigate. This could be done; it isn’t.

Science in Action: Omega-3 (sleep data)

Seth RobertsLeave a comment

When I started taking omega-3 the rationale was not crystal clear. Many Shangri-La dieters reported better sleep; the diet involves drinking fat; omega-3, a fat, may affect the brain; sleep is controlled by the brain. I had not noticed any change in my sleep when I switched from sugar water to ELOO. Maybe this was because ELOO was low in omega-3, I thought, and this is what prompted my interest in omega-3. Later, a fly in the ointment: a poll of SLDers found that ELOO was as likely to produce better sleep as other oils. Implying that it is not omega-3 that is producing better sleep. I was puzzled, but continued my omega-3 investigations, which by then were motivated by an unmistakable improvement in my balance. My sleep did seem to improve somewhat when I started taking flaxseed oil capsules (a good source of omega-3).

Now I think I understand. I recently changed the time of day that I take 3 tablespoons of flaxseed oil. I had been taking it around 10 pm every evening; I switched to 10 am every morning. I wondered if the change would affect my balance, which I test around 7 am every morning.

To my surprise the change affected my sleep: I started waking up earlier. That is, I slept fewer hours before I woke up. This was not good — in general, the longer I sleep in one continuous stretch at night, the better. I was waking earlier and less rested. My impression was that my sleep was reverting to an earlier, lower-quality state.

To confirm this, I entered a lot of my sleep data into my computer and made a graph of how the length of my sleep (my “1st” sleep, to distinguish it from sleep when I fall back asleep a few hours after waking up) varied over the last two years. Here is the graph:

Length of 1st sleep over time

T = tablespoon. The labels give the daily dose — e.g. “3 T flax” means 3 tablespoons/day of flaxseed oil. Each point is a mean. The error bars are standard errors. This graph shows that in recent months I had been sleeping longer. I had noticed this change: it was especially clear when I switched from 1 T/day flaxseed oil to 2 T/day. I thought the improvement was due to omega-3 — ignoring the fact that a switch to sesame oil (low in omega-3) didn’t eliminate it.

Now, with a third fact contradicting my original idea (the first two were the poll and the sesame oil results), I have finally managed to change my mind. It is fat in the evening that causes longer sleep. Not only omega-3 fat — perhaps any fat has this effect. Now all sorts of things make sense.

  • When I started drinking ELOO my sleep didn’t improve because I drank most of the ELOO during the day.
  • When I started the flaxseed oil capsules they had only a little effect on my sleep because I swallowed them throughout day as well as in the evening.
  • When I switched from 10 flaxseed oil capsules per day to 1 Tablespoon of flaxseed oil per day my sleep got longer because I always drank the tablespoon in one shot — around 10 pm. When I switched to 2 Tablespoons/day, I continued to drink it all at one time, around 10 pm. I attributed the improvement to the increase in omega-3; it was really due to the increased evening intake of fat.
  • ELOO and other fats helped many SLDers sleep better because they drank them in the evening.

    • If you want to try this, note that the effect was bigger with 2 tablespoons at 10 pm than with 1 tablespoon at 10 pm.

    To be continued.

    Human Nature vs. Self-Experimentation

    Seth RobertsLeave a comment

    In all modesty, here is Tyler Cowen’s recent post about self-experimentation, especially mine. I don’t know enough about philosophy to comment on the philosophical stuff but I agree with the rest of it — especially the reference to Robin Hanson, who argues that our biases badly distort our reasoning. Sure, self-experimentation doesn’t fit the usual research model. It doesn’t need grants or graduate students. It doesn’t generate publications quickly. But what if you are a scientist and you sleep badly, or you’re depressed, or you want to lose weight? Why not self-experiment to try to find a solution? Your career won’t suffer; you can do it in your spare time. Your life might benefit. Why this has not happened is the puzzle.

    Tyler mentions status-quo bias. I would add two more. They are hedonic biases rather than cognitive ones: biases in what we enjoy. They are restricted to men; women are quite different:

  • Big things are more enjoyable than small things. This is rationalized into a belief that big things are more important, more worthy of study and support, than small things. I live on a steep street. One day a really big truck got stuck. When I came upon it, there were fifteen-odd people on the street just standing there, looking at it. Not a female among them. Treating big things better than small things I call bigism. Tyler’s view that a tiny restaurant had something to teach him is the opposite of bigism.
  • Admission of weakness is unpleasant. It is undignified. It is un-stoic. It is too personal. Taken to extremes, it is humiliating. I self-experimented on sleep and weight because I slept poorly and weighed too much. Telling others what I had done was an admission of weakness. Unavoidable, of course, but I too have this bias. Whenever anyone says I self-experimented with mood because I was depressed I quickly correct them.