In China, a two-day annual test, which ended Friday, determines what college high school graduates will attend. Outside a test site, an AP reporter heard this:

Wang said she has been cooking foods for her son that are considered particularly good for worn-out students, with plenty of vegetables and less grease.

“Oily foods, it’s bad for the brain, it makes the brain slow down,” she said.

Astute observation. Regular readers of this blog know that certain oily foods (those high in omega-3 fats) have the opposite effect. But I suspect Ms. Wang is right, that most oily foods (high in omega-6) do slow the brain down, perhaps because they replace omega-3 with omega-6.

I blogged earlier about comparing flaxseed oil and nothing: here are the balance and arithmetic results. I also used a paper-and-pencil memory-scanning task that I described earlier. Here are the flaxseed vs. nothing results from that task:

The difference was even clearer — t = 8 — than with the other measures (balance, t = 7; arithmetic, t = 6). It took about three days of no flaxseed oil before its effect completely wore off, but only one day of resumption to reach full strength again — the pattern seen several times earlier.

The test took 5 minutes/day, twice as long as the arithmetic problems but only half as long as the balance test. The equipment demands are mild: printer, pencil and paper (in addition to computer).

I’ll discuss the implications in a later post.

Flaxseed oil increased how fast I did simple arithmetic problems (e.g., 7+5, 9-4, 3*7). To better measure the effects of fats on my brain, I wanted to find out which problems were most sensitive to flaxseed oil. Then I could hope to create a more sensitive test.

Before looking at the data, I assumed that problems that required more processing — more time — would be more sensitive. But this was not what I found.

First, I compared problems with different functions — plus, minus, and times. (E.g., 5+4 is a plus problem.) Sensitivities:

function….F…..n
plus……..15…..1400
minus…….9…..1400
times……16…..1400

The F values are for the flaxseed/nothing comparison. Greater F = more sensitive. The n values are the number of trials. These results more or less agreed with my preconceptions: times problems were slower than the others.

Then I compared problems based on their correct answers. I divided the problems into groups with roughly equal number of trials. Sensitivities:

answer…F……n
0-3 …..12….1000
4-6……15….700
7-9……..6….900
10-19…..2….900
>19……13….500

This was the surprise: Problems with answers 10-19 contributed almost nothing to the overall sensitivity, while problems with answers on both sides contributed much more. Was typing “1″ the problem? No, problems with the single-digit answer “1″ were no worse than problems with similar one-digit answers.

I redid the analysis omitting problems with answers 10-19 and found more sensitivity to the effects of flaxseed oil — a slightly larger F (or t) value, even though the number of trials was 20% less. Here is a graph based on the more sensitive analysis:

No important differences from the earlier, less sensitive analysis:

Based on these results I will get rid of the subtraction problems and the problems with answers from 10-19. I haven’t decided whether I will keep the total number of problems the same; I might increase the number (which is now 100 — 100 arithmetic problems per session).

I recently posted that flaxseed oil affected how fast I did simple arithmetic problems (a way to measure brain function). Someone asked to see the R programs I used. Here they are.

> arithmetic.add
function (trials=100, condition = “test2″, procedure = “no mistake correction”,note=””)
{# collect new arithmetic data
#
invisible()
start.time=Sys.time()
condition=new.condition()
start.expt()
trls=sample(rep(c(“+”,”-”,”*”),times=c(34,34,34)),size=trials)#determine trial sequence
t=arithmetic[1,]for (tr in 1:trials){
t2=c(current(),condition=condition,procedure=procedure,trial=tr,arithmetic.new.line(func=trls[tr]),note=note)
t=rbind(t,t2)
}
arithmetic<<-rbind(arithmetic,t[-1,])
save.ws()
arithmetic.plot()
cat(“total time”,round(difftime(Sys.time(),start.time, unit=”mins”)),”minutes\n”)
}

> new.condition
function (conditions.so.far = arithmetic$condition)
{# get new condition name
#
# conditions.so.far vector of conditions so far
#
cat(“most recent condition”,last(conditions.so.far),”\nthis condition”)
condition=scan(nlines=1,what=”character”,quiet=TRUE, sep=”!”)
condition
}

> start.expt
function ()
{#wait for Enter to start data collection
#
cat(“press Enter to start “); scan(quiet=TRUE)
}

> arithmetic.new.line
function (func=”+”)
{# give addition, subtraction, or multiplication problem
#
# func function
#
b=sample(0:9,2)
if(func==”+”) answ=b[1]+b[2]if(func==”-”) {b[1]=b[1]+b[2];answ=b[1]-b[2]}
if(func==”*”) answ=b[1]*b[2]start.time=Sys.time()
cat(b[1],func,b[2],”= “)
a=scan(n=1, what = “integer”, quiet = TRUE)
msec=as.integer(1000*difftime(Sys.time(),start.time,unit=”sec”))
correct=a==answ
if(!correct) print(correct)
list(type=func,first.num=b[1],second.num=b[2], msec=msec, answer=as.integer(a),correct=correct)
}

function (vec, n = 1, drop = 0)
{#return last n elements of vec
#
# vec vector
# n number of elements
# drop elements at end to drop before taking n elements
#
le=length(vec)
okay.le=le-drop
vec=vec[1:okay.le]le=length(vec)
ind=(1+le-n):le
vec[ind]}

If you would like help using these programs, please contact me.

Here are more results from my comparison of flaxseed oil with nothing. I wrote earlier about the balance results.

Each day I measured how quickly I could do each of 100 simple arithmetic problems (e.g., 2+7, 5-2, 5*6). I learned about this task from Tim Lundeen. Tim did the task with paper and pencil whereas I used R (a statistics-oriented language) on my laptop to do the experiment: For each problem, I typed the answer and then hit return. “FALSE” was printed if I made a mistake. The next problem appeared immediately.

Here are the average solution times:

There was a very clear difference, t = 6. It took more than one day for the effect to become clear, in contrast to the balance results, where it took more than two days.

These results confirm what Tim found. Unlike what he did and my balance measurements, no special equipment was used (besides a computer). This may be the easiest way to study the effect.

My balance results have obvious practical value: Old people often seriously hurt themselves due to loss of balance. What about these results? Well, failure to react fast enough causes many car accidents. Flaxseed oil (and probably other sources of omega-3) may make you a better driver.

Directory of my omega-3 posts.

Do our brains need more omega-3? I have blogged about this many times. My first two self-experiments to answer this question compared flaxseed oil (high in omega-3) with olive oil or sesame oil (low in omega-3). My balance was better with flaxseed oil, suggesting the answer is yes. However, another interpretation is (a) flaxseed oil had no effect and (b) sesame oil and olive oil made my balance worse. To test this possibility, I compared flaxseed oil to nothing (no supplement). If flaxseed oil has no effect, the two conditions should be the same. If flaxseed oil improves my balance, my balance should be better during the flaxseed-oil condition.

During the flaxseed-oil condition, I drank 4 tablespoons/day of flaxseed oil — 2 at 10 am, 2 at 10 pm. The balance test was at 8 am the next day. During both conditions, I did not eat fish.

Here are the results:

There was a large and very clear difference between the conditions. It took about three days of no flaxseed oil before the difference stopped increasing. On the first day of resumption of the flaxseed oil, my balance was much better than the day before. Comparing the two conditions (omitting the first three days of the nothing condition), t = 7.

These results support the idea that flaxseed oil made my brain work better.

Are injury-causing falls the new scurvy? The large fast improvement in my balance when I resumed flaxseed oil does resemble the large fast improvement when a person with scurvy eats oranges.

I was surprised by the time course of the decrement during the no-flaxseed condition: It looks different than what happened when I drank olive oil. In this experiment, my balance got worse for about 3 days and then stopped getting worse. In the previous experiment, my balance appeared to get worse for at least 9 days. This may due to the high omega-6 content of olive oil — omega-6 (almost identical to omega-3) may displace omega-3. In the absence of omega-6, omega-3 takes longer to deplete.