Hey, What Happened to My Brain?
Seth Roberts
For a few months, I've been measuring how well my brain is working using arithmetic problems. Each test session includes 100 simple problems (3+4, 7-0, 4*8) divided into 5 blocks of 20. I type the last digit of the answer as quickly as possible. I got the idea from Tim Lundeen, who got better on a similar task when he increased his DHA intake. My performance on an earlier version of this task was improved by flaxseed oil.I've blogged about this. The virtues of this test include: 1. Fast. Takes only a few minutes. 2. Portable. Requires only a laptop. 3. Many possible answers (1, 2, 3, etc.). This reduces anticipation errors. 4. Many numbers (reaction times) per test. This allows me to get a measure of variability for each session and can correct for the difficulty of the problem. Aspects with room for improvement include: 1. Speed/accuracy tradeoff. Accuracy isn't fixed. Depending on how accurate I want to be, I'll go faster or slower. (I aim for 95% correct.) 2. No complex actions. The most enjoyable games have a motor-skill aspect that this task does
not.
Here's the data so far.
The big gap happened because I moved from Beijing to Berkeley. The most
fascinating result, of course, is the sudden drop on February 2. Here
is a close-up.
What might have caused this? The first test with better performance took
place while my landlady, who lives upstairs, was practicing piano.
Usually it's quiet when I test myself. My first thought was that the
music had caused the improvement. But it persisted so long after the
music had stopped that the music couldn't be the cause.
It's really plausible that the improvement was due to the change in flaxseed oils. Flaxseed oil had made a difference (versus nothing) with a very similar task. A few weeks before the shift, a friend had asked how I knew if my Chinese flaxseed oil was good; I'd said I'd find out when I switched back to Spectrum Organic.
But why was the improvement delayed four days? I started studying flaxseed oil because one evening I took several capsules and the next morning noticed my balance was better. And if the improvement is going to take that long, why would it happen so sharply after the delay? I can't even begin to answer these questions.
Standard errors based on what?
The bars are standard errors.
How unusual is such a change? I’ve never seen anything like it in behavioral data.
Maybe it’s hard to see in the graphs here but my performance had stabilized in China. In other words, I had stopped improving.
Thanks Seth for this great post. I know from reading your post on sethroberts.net that you use R, the open source statistics software, on a windows laptop, to do your measurements. I am on a mac, and despite your generous help I never got comfortable in R. (I keep my other data in an excel spreadsheet.)
I think a popular, standard version of this test would be really useful. It is not much different from what they have done in Brainage but with set parameters.
An alternative hypothesis is that those low values are just what you’d expect if you hadn’t moved to Berkeley (based on extending the previous exponential trend by eye). The unusual pattern is the increase at the end of January - and you have a good explanation for this.
That still fails to explain the suddenness of the drop, but how unusual is such a sudden change? We need more data (or at least your data). Visually, the change maybe amplified by the vertical bars you are drawing, and the irregularity of sampling over time. (And what are those bars?)