Vladimir Putin, have a sandwich.
I'm Angela Duckworth.
I'm Steven Dubner.
And you're listening to No Stupid Questions.
Today on the show, can you train your brain to focus for a longer period of time?
I used every single ounce of my physical and mental energy and I have nothing left.
Angela, you and I have both read a new working paper by four economists, Christina Brown,
Supreet Kaur, Gita Kingdon, and Heather Schofield about what's called cognitive endurance,
which was a phrase that captured my attention.
A good phrase, yeah.
It's a very good phrase.
Is there a generally accepted definition of that in the academic or psychological realm?
They defined it as, quote, the ability to sustain
effortful mental activity over a continuous stretch of time.
The paper makes two primary arguments.
One, that students from low income backgrounds exhibit what is called cognitive fatigue
more quickly than high income students.
But point two, cognitive endurance is essentially, as I understand it,
at least a muscle that anyone can build up.
So because cognitive endurance sounds to me, at least a lot like grit, I wanted to hear
what you have to say about this research, what it means for anyone who would like to increase
their own cognitive endurance, whether in an educational setting or otherwise.
So maybe we could just start with your describing what the study actually showed and we can take
it from there.
Gosh, you had me at hello.
Like this title, cognitive endurance as human capital is like porn for me.
I can't resist.
It's titillating.
So here's the first line.
Schooling may build human capital not only by teaching academic skills,
but by expanding the capacity for cognition itself.
It's a bold claim to say, maybe one of the most important reasons why we go to school
is to build up this thing called cognitive endurance.
The ability, as these authors say, to sustain effortful mental activity over a continuous
stretch of time.
And I've been thinking about this paper since I read it a few weeks ago.
They randomly assigned elementary school students in India to different conditions.
In one condition, these kids were asked to do something which basically the experimenters,
the economists here thought was like, it's training.
Like, let's give them cognitively hard stuff to do over 20 or 30 hours and then there'll
be a control group.
And at the end, we'll see who has more of this cognitive stick to it.
So it'd be the equivalent of if you're trying to train someone physically saying,
I'm going to take a group of you, randomize you, split you in half.
And then a bunch of you are going to do 100 pushups a day and 100 sit ups a day over
the course of a few hours.
And the rest of you are just not.
And then we'll go out and we'll do feats of strength and see how you do.
Is it that cut and dried?
Well, you know, there is not the language of like, it's a muscle, but absolutely,
I think that's the mental imagery.
Can you talk about for a moment what the actual endurance building tasks were and how
typical they were for an educational setting?
In other words, are these the kind of things that some schools are already doing a lot
and others aren't or are they separate from typical education tasks?
So in the treatment condition, the cognitive endurance training condition,
these kids were given 20 to 30 hours of hard cognitive work.
The majority of them were doing math problems.
It was on tablets.
And when you get something right, it levels you up.
It's almost like you go to your physical trainer and as soon as you can lift five pounds,
they move you up to eight pounds or something like that.
So it's getting harder as you get better to maintain this cognitive load.
There was another cognitive endurance training condition where you did
luminosity kind of games, but not luminosity.
They call them non-academic games,
which they describe as providing a pure test of our mechanism.
In other words, can you learn to focus and engage for a longer period?
Is that what that means?
Yeah, they were trying to give you cognitively challenging tasks,
but not like what you usually do in elementary school.
They were trying to isolate just cognitive effort by itself.
You know, it's interesting to me about that second treatment and that type of task.
Is that it does sound quite familiar to those of us, whether as kids or as parents or as educators,
who've heard these arguments about the reason you should play a musical instrument when you're six
years old or the reason you should play sports.
There are all these different functions that are not really about musicality and not really about
athleticism. It's about learning skill, focus, teamwork, commitment, on and on and on and on.
So that was also interesting to me that they wrote that these non-academic games were,
quote, a pure test of our mechanism, because I'm very curious to know
about the generalizability of this finding.
You're absolutely right, Stephen. What parent sends their kid
to violin lessons because you're going to be a violinist?
Oh, I know a couple.
But the vast majority, I hope they're sending them for this like meta stuff.
You're going to learn how to do hard things.
You're going to learn how to win and to lose.
So I do think this games practice, which was an alternative to the math practice,
but both of them were supposed to build endurance.
I think it's interesting how closely that resembles the whole extracurricular function
that at least American parents do a lot of.
So those are the treatment conditions, 20 to 30 hours.
It's all done on an iPad kind of tablet.
They disabled features.
So it wasn't like these 20 to 30 hours were necessarily fun.
They strenuously point out that there were no fancy animations.
You couldn't surf the web.
So not particularly fun training.
This reminds me, since we're talking about a paper here, which argues that
students from low income backgrounds exhibit what's called cognitive fatigue more quickly.
This paper feels like part of a literature that I'm sure you know quite a bit about,
which is the literature arguing that poverty itself is just exhausting.
There's a paper by Sandal Melanitan, Elder Shafir, and a couple other authors.
The title of that paper is Poverty Impedes Cognitive Function.
The idea that being poor is essentially exhausting.
There's so much effort and cognitive effort into just getting by.
It really was such an important finding that being poor is not only an emotional burden,
it's a cognitive burden.
And the way they tested this was they tested how farmers did in different times of weather,
like after a drought.
So if I see that a farmer is doing worse on cognitive function tasks when things are bad
in the climate, no harvest, the weather is terrible, but not because of anything you did
or didn't do, then I have evidence that there is a cognitive load to poverty.
And that's what they found.
But importantly, it opened up this possibility that maybe one reason why kids in school from
disadvantaged backgrounds aren't doing well is maybe that there's a cognitive
load to what they have to deal with.
They're thinking about a million problems that privileged kids may not be.
But it's very complicated because just knowing that alone,
if you're like, wait, if self-control is like a muscle and these kids are lifting
around cognitive barbells, that would lead you to the conclusion that poor kids should have
stronger muscles because of all the things that they've had to deal with.
That's a great point.
But you also just noted how complicated it is.
And one complication that this new paper that we're talking about points out is that some
schools are much better at essentially training students to have more cognitive endurance.
And no surprise at all, schools where higher income students go to tend to be the schools
that are much better at teaching that.
And let me say something that I think will help.
We're very attracted to metaphors like cognitive endurance is like a muscle.
You strengthen it with use and repetition.
But in the short term, when you're doing that strength training,
maybe in that five minute period after you've just done something cognitively hard,
you're kind of exhausted.
You're depleted.
I think that's not the right metaphor.
And I think when we try and understand the experience of kids who are poor
and these farmers and what cognitive endurance really is,
it's not like self-control is an actual muscle.
It's not an actual energy source.
In some ways, it behaves like that.
I think when we feel feelings of fatigue and you have felt it, I have felt it.
I remember what it was like to take the SAT.
You like stagger out of the exam room and all you want to do is sleep.
And I know it feels like there's some kind of muscle that got worn out with use.
But I think all feelings are mental representations.
It's like a signal.
And in this case, fatigue generally signals, hey, you've just done something that took a lot of
intention and a lot of energy.
Maybe you should do something else because the return on investment in something else
might be more beneficial.
It's so interesting.
It reminds me of something that happened just yesterday.
I was playing golf up at my club and it was championship Sunday.
It was the finals of all these brackets.
And the last group to come in were these two fellows.
I didn't know who'd won.
And one of them pulled up in his golf cart.
And I know this guy fairly well.
He's a lovely older gentleman, very good golfer, very polite, very generous.
He's never thinking of himself first, I guess I would say.
But yesterday, he pulled up in the golf cart.
I said, hey, Rick, how'd you do?
And he just did a thumbs up, no word, meaning he won his match.
He's a champion in his bracket.
And then it was time to come over to take pictures.
Every winner got to stand there with a trophy and take a picture.
And someone said something to Rick and he's also very pleasant.
Just a nice smile.
Always in this case, no smile at all.
And when someone said something to him, he said, I'm sorry, I'm just so out of it in my match.
I was down five after 10 holes, which is essentially an insurmountable deficit.
And yet he came back to when he said, I used every single ounce of my physical and mental energy
and I have nothing left.
And it was so amazing to see this person have a totally different character in the moment.
He was like a zombie.
He seems spent, makes you believe in that metaphor, doesn't it?
And he put it perfectly.
It wasn't just the physical.
It was the mental.
The stress of coming back from that deficit had just used up everything you had.
And so you realize plainly there are limits to this.
As you said, it's more complicated than a muscle, but if it's more complicated than a muscle,
how would you describe it, especially for those of us who
want to use it for something outside of school?
Is it more like a skill?
Is it more of a preference?
Like I choose to have cognitive endurance.
How do you begin to think about the complication of what cognitive endurance is
and how it can therefore be boosted?
So here's what I think is going on with, I'm sorry, who was this distinguished golfer?
His name is Rick.
And I'll give his last name because I was very proud of him and he's a good guy.
His name is Rick Powers.
Oh, great name, Rick Powers.
Maybe his middle name is cognitive.
Yes, maybe it is.
So Rick, I know was experiencing mental fatigue.
I mean, he said so.
What was going on there?
I'm saying there was a signal that his brain was saying, like, hey, Rick, you know what?
You're in a position of having just expended tons of energy and attention toward the same
goddamn thing.
And you might want to think about doing something else or potentially, I mean,
look, I don't know how hard he was concentrating.
I do think at outer bound limits, there could be something where your mind really
can't sustain activity anymore.
But what I want to say about the signal is it goes off well before it's anywhere close
to its limit.
Let me tell you about another person, and they're not a golfer and they're not a guy.
There was a graduate student, I believe, at Columbia University.
I don't remember her first name, but her last name was Arai A-R-A-I.
And she did for her PhD this dissertation on cognitive endurance and cognitive fatigue.
And back in the day, this is like 1912 that it was published.
You often did psychology just to yourself.
You're like, I wonder what it's like to do this.
I guess I'll do it.
And so what she did was she trained herself to do four-digit by four-digit mental
math multiplication.
So imagine, Steven, 1,872 times 7,641.
Solve that problem in your head without using paper and pencil.
All right, 14,303,952.
You're a genius.
By the way, Arai did this well before Google.
What she was doing is she was just setting herself up to do incredibly mentally effortful
activity.
She trained herself up to a level of competence where she was getting things right and not
getting any better.
And then what she did, Steven, is she sat in a room and she did these math problems in her head
one after the other only with occasional breaks to go to the bathroom or eat a sandwich.
And then she would go right back to it.
She plotted her accuracy on a graph.
Like, how did she do?
Hour one, hour two, hour three.
And she did this for hours in a row on consecutive days.
And what did she find?
Did she get better?
Did she stay flat?
Or did she go down?
I will give you this clue.
Each of the days really pretty much resembled each other.
So you could just take a snapshot of one of those.
So what did the graph look like?
I would imagine it's a slightly unequal parabola.
Meaning I would think that she probably peaked before the midpoint and then kind of held
steady and then began to fall toward the end.
That's what I would guess.
She started off strong and just got worse.
There was like a little uptick.
I think it was after lunch.
I mean, isn't the moral of almost every story have a sandwich?
Yes, I really think that many of the world's problems would be solved by turkey and cheese.
Vladimir Putin, have a sandwich.
But anyway, the idea of Arai's thesis was that there was a kind of strength that was depleted.
And by the way, the reason why your parabola thing did not happen is that,
remember, she had pre-trained for this.
She had got-
