Today one of my students almost fell asleep: She, simply, was mentally exhausted after mimicking me for 10 minutes. The improvements she made during that time, though, were massive. By the end the she had close to native-level pronunciation for the 20 words we studied.

This episode made me wonder: What I am doing wrong? I never get that tired after ten minutes of Skritter. How do I engage my brain so that I need to take a nap afterwards? I must be tuning too many things out.

Interesting article I recently read just on this subject.

http://www.scientificamerican.com/article.cfm?id=thinking-hard-calories

It's well written but the premise is flawed.

I used to be a wrestling coach. At the end of each season I could easily wrestle for over an hour -- with sporadic breaks -- without getting too fatigued. However, at the same time, I couldn't swim all the way across a pool without grabbing on to the buoys. Muscle endurance is sports specific. The same occurs with language. My English endurance is outstanding; I can't speak longer than a few minutes in Japanese before my brain hurts.

Since I have been in Japan, I have slept over 10 hours a night a few times each month. One night, after I moved while in Japan, I slept for over 14 hours! I have not slept that much since I was a child.

icecream, i think you are misinterpreting the study. It did not measure the feeling of exhaustion (which you felt swimming but not wrestling); rather, it measured the amount of calories burned.

The results demonstrate that caloric expenditure in the brain is the same, regardless if one is resting or engaging in an activity that requires heavy concentration. This would be like your body burning the same amount of calories in 20 minutes of resting on a couch as you would in 20 minutes of running up a flight of stairs.

Regardless of your endurance abilities while wrestling, you were surely burning more calories than you would be sitting on a couch. Also, all of the concentration activities performed in the lab were devised by the researchers, so the participants had no experience in them and no chance to have a "higher" tolerance (as you do with wrestling).

The article goes on to say the feeling of mental exhaustion is a real phenomenon, but can't as yet be proven to be simply caused by physical mental exertion. Instead, the feeling seems to have a more complex cause, and the article provides a few guesses.

It’s not one study. There were many studies. The entire article is just a rehash of a bunch of semi recent findings in neuroscience. It’s a fluff piece. I have nothing against Scientific American – I have an issue in my room here in Japan that my mom sent me – or the research they are trying to interpret. I simply disagree with the claim that mental exhaustion is in one’s head.

I’m not arguing about whether or not calorie expenditure is the same or not. That’s not the issue. The issue is simply how to induce mental exhaustion.

An interesting topic! What is mental fatigue? What limits the number of things we can learn in one go? It seems clear there is a limit to what I can learn, and that sleeping helps my learning process. I imagine sleep facilitates a kind of "background rearranging" of my mental structures, a bit like disk defragmentation on a PC :-)

Possibly related topics:
http://en.wikipedia.org/wiki/Decision_fatigue
http://en.wikipedia.org/wiki/Ego_depletion

As for what makes for exhausting study, I wonder if there is a mental equivalent of the opposition between strength vs. endurance workouts, where a strength workout is short and intense and requires a two-day rest for muscles to repair and become stronger, while an endurance workout is longer but less intense.

@ Kai Carver

From my own personal experiences, I think there is a mental equivalent of strength and endurance. When I am reviewing old material I enjoy listening to long stretches of dialogue and can easily handle multiple individuals speaking in different voices. I can easily paraphrase the conversations with differing levels of abstraction. However, if they use new vocabulary my brain starts to falter and I get bogged down with details and become unable to differentiate between what’s important and what’s not.

So to sum up. Old material is endurance work; new material is strength work.

10 minutes! lol
I would understand if she was mentally exhausted after 10 hours but 10 minutes is a joke. Your student needs to get some sleep before class and toughen up.

The best way I've found to concentrate longer is to push yourself and get used to really long or all day sessions. Afterwards you find those short sessions, which were once hard, are now easy to do.

Today, after doing a few sets of bench presses, my chest started to twitch. My muscle fibers couldn’t handle lifting a heavy weight for more than a few reps. At lunch I was still so fatigued that my arms were shaking as if I was a Parkinson’s patient. Can you sprint for 10 minutes? It’s impossible; your body will give out.

The same occurs with learning a new language: your brain can’t handle learning something at an intensity that is too high. You simply need time for your brain to mentally recover. Learning new words is more like a mental sprint than a marathon.

習うより慣れろ＾＾