Which is most effective for helping people learn: punishment or reward?
Which is most effective for helping people learn: punishment or reward?

Well, consider the case of Israeli fighter pilot training, because instructors there
Well, consider the case of Israeli fighter pilot training, because instructors there

found that negative feedback was far superior to positive feedback.
found that negative feedback was far superior to positive feedback.

If a cadet performed a particularly poor maneuver they would reprimand him.
If a cadet performed a particularly poor maneuver they would reprimand him.

But they noticed that on follow up attempts, his performance invariably improved.
But they noticed that on follow up attempts, his performance invariably improved.

In contrast, if they praised a cadet for executing a skillful maneuver, his performance on subsequent
In contrast, if they praised a cadet for executing a skillful maneuver, his performance on subsequent

attempts typically declined.
attempts typically declined.

So naturally they concluded that positive feedback is ineffective or even detrimental
So naturally they concluded that positive feedback is ineffective or even detrimental

whereas negative feedback is what works.
whereas negative feedback is what works.

The problem is this seems to contradict a body of research that shows positive feedback
The problem is this seems to contradict a body of research that shows positive feedback

is actually more effective than negative feedback.
is actually more effective than negative feedback.

For example, in studies involving teachers it was found that if a teacher increase the
For example, in studies involving teachers it was found that if a teacher increase the

ratio of positive feedback to negative feedback, that actually increases the percentage of
ratio of positive feedback to negative feedback, that actually increases the percentage of

times students spend on task.
times students spend on task.

In another study rugby players were given a video feedback session following a game,
In another study rugby players were given a video feedback session following a game,

except half of them were shown their highlights and they were praised for what they had done
except half of them were shown their highlights and they were praised for what they had done

and the other half were shown their biggest blunders, their mistakes.
and the other half were shown their biggest blunders, their mistakes.

And they were scolded for doing things incorrectly.
And they were scolded for doing things incorrectly.

Now a week later at the next game, it was the players who had received the positive
Now a week later at the next game, it was the players who had received the positive

reinforcement who performed the best.
reinforcement who performed the best.

And, in fact, the difference was not just psychological.
And, in fact, the difference was not just psychological.

Blood tests revealed that the players who received positive feedback actually had higher
Blood tests revealed that the players who received positive feedback actually had higher

levels of testosterone than players who had received the negative feedback.
levels of testosterone than players who had received the negative feedback.

I think that is quite remarkable that even a week post feedback you could still see a
I think that is quite remarkable that even a week post feedback you could still see a

physiological difference between the two types of feedback.
physiological difference between the two types of feedback.

Wow.
Wow.

Well so why didn't this work for the Israeli fighter pilots?
Well so why didn't this work for the Israeli fighter pilots?

Well, maybe there are cultural differences and in some cultures negative feedback works
Well, maybe there are cultural differences and in some cultures negative feedback works

better.
better.

Or maybe it is task dependent.
Or maybe it is task dependent.

Perhaps some skills like learning to fly a fighter jet require more negative feedback.
Perhaps some skills like learning to fly a fighter jet require more negative feedback.

Or maybe the feedback had nothing to do with the performance of the fighter pilots at all.
Or maybe the feedback had nothing to do with the performance of the fighter pilots at all.

Maybe they would have performed in the same way regardless of the feedback they received.
Maybe they would have performed in the same way regardless of the feedback they received.

Go with me on this.
Go with me on this.

Imagine you have 100 students taking a test which consists of 100 true or false questions
Imagine you have 100 students taking a test which consists of 100 true or false questions

on a subject they know nothing about.
on a subject they know nothing about.

Now assuming they all answer randomly, we know that the resulting distribution of scores
Now assuming they all answer randomly, we know that the resulting distribution of scores

will have an average of around 50.
will have an average of around 50.

But just by chance, some students will have scored significantly better or worse than
But just by chance, some students will have scored significantly better or worse than

the average.
the average.

>> Oh, man.
>> Oh, man.

>> If you select the top 10 students whose scores were all above 50 and gave them a second
>> If you select the top 10 students whose scores were all above 50 and gave them a second

very similar test, you would find that the average of their scores would drop back to
very similar test, you would find that the average of their scores would drop back to

around 50.
around 50.

Similarly, if you selected the bottom 10 students, their score on a subsequent test would rise
Similarly, if you selected the bottom 10 students, their score on a subsequent test would rise

to 50.
to 50.

This is just regression to the mean.
This is just regression to the mean.

Regression to the mean is the reason why if you have a really good round of golf today,
Regression to the mean is the reason why if you have a really good round of golf today,

your round tomorrow will not be as good.
your round tomorrow will not be as good.

Yes.
Yes.

That is because random chance plays a role in virtually everything that we do.
That is because random chance plays a role in virtually everything that we do.

So the outcomes of events are influenced by both our skill and a little bit of luck.
So the outcomes of events are influenced by both our skill and a little bit of luck.

So if you have especially good luck on one day, chances are your level of luck will not
So if you have especially good luck on one day, chances are your level of luck will not

be as good the next day.
be as good the next day.

Now that sounds a little bit like the gamblers fallacy, which states that past events influence
Now that sounds a little bit like the gamblers fallacy, which states that past events influence

future probabilities.
future probabilities.

For example, if you flip a coin and it comes up tails a couple of times, the gamblers fallacy
For example, if you flip a coin and it comes up tails a couple of times, the gamblers fallacy

is to expect the probability of heads to increase for the next flip.
is to expect the probability of heads to increase for the next flip.

In reality it doesn’t.
In reality it doesn’t.

It is still 50-50.
It is still 50-50.

The idea wit the gamblers fallacy is that probabilities change so that overall things
The idea wit the gamblers fallacy is that probabilities change so that overall things

over out in the long run.
over out in the long run.

That is the idea.
That is the idea.

With regression to the mean, it is not that things are evening out, it is just that extreme
With regression to the mean, it is not that things are evening out, it is just that extreme

events are becoming diluted by the average events which happen much more commonly.
events are becoming diluted by the average events which happen much more commonly.

Now with these students they were completely guessing on every question.
Now with these students they were completely guessing on every question.

But even when you know something about the subject, there is still going to be there
But even when you know something about the subject, there is still going to be there

that element of chance.
that element of chance.

And so regression to the mean always occurs, just to a lesser extent.
And so regression to the mean always occurs, just to a lesser extent.

This is really important to consider in research.
This is really important to consider in research.

Imagine you are trialing a new drug to help prevent heart disease.
Imagine you are trialing a new drug to help prevent heart disease.

So from a sample of patients you select those in the bottom 10 percent of heart health indicators,
So from a sample of patients you select those in the bottom 10 percent of heart health indicators,

people with high blood pressure, high cholesterol, that sort of thing.
people with high blood pressure, high cholesterol, that sort of thing.

Now after a month of being on a drug, you test them again to find that their scores
Now after a month of being on a drug, you test them again to find that their scores

have improved.
have improved.

Well, great, the drug is working, right?
Well, great, the drug is working, right?

Well, maybe not.
Well, maybe not.

See, the trouble is that although blood pressure and cholesterol are more stable than, say,
See, the trouble is that although blood pressure and cholesterol are more stable than, say,

your score on a random true or false test, there is still some inherent variability caused
your score on a random true or false test, there is still some inherent variability caused

by, say, your level of stress on the day or your recent diet or even the uncertainties
by, say, your level of stress on the day or your recent diet or even the uncertainties

introduced by the measuring apparatus.
introduced by the measuring apparatus.

So the people who ended up in the bottom 10 percent on the first test, likely had these
So the people who ended up in the bottom 10 percent on the first test, likely had these

factors all count against them.
factors all count against them.

They were particularly unlucky.
They were particularly unlucky.

But you should not expect them to be as unlucky when you test them a second time.
But you should not expect them to be as unlucky when you test them a second time.

So their scores should improve just based on random chance.
So their scores should improve just based on random chance.

That is why it is so important that clinical trials use control groups drawn from exactly
That is why it is so important that clinical trials use control groups drawn from exactly

the same population so that you can see whether the drug improves scores more than random
the same population so that you can see whether the drug improves scores more than random

chance alone would.
chance alone would.

Or what about the assessing the impact of speed cameras?
Or what about the assessing the impact of speed cameras?

When they are first installed, they are normally put in locations that have had a high volume
When they are first installed, they are normally put in locations that have had a high volume

of accidents in the previous year or two.
of accidents in the previous year or two.

Makes sense.
Makes sense.

Now those accidents are likely due, at least in part, to bad road design, but also due,
Now those accidents are likely due, at least in part, to bad road design, but also due,

at least in part, to bad luck.
at least in part, to bad luck.

And so you shouldn’t be surprised that after a speed camera is installed the number of
And so you shouldn’t be surprised that after a speed camera is installed the number of

accidents goes down.
accidents goes down.

It would go down anyway simply due to regression to the mean.
It would go down anyway simply due to regression to the mean.

Meanwhile somewhere else that previously had a small number of accidents will likely have
Meanwhile somewhere else that previously had a small number of accidents will likely have

more.
more.

So the overall accident rate may not change and yet we will feel as though our investment
So the overall accident rate may not change and yet we will feel as though our investment

in road safety has paid off.
in road safety has paid off.

But perhaps what is most troubling about regression to the mean is how it influences our perception
But perhaps what is most troubling about regression to the mean is how it influences our perception

of feedback.
of feedback.

For example, with the fighter pilots, after they execute a maneuver particularly poorly
For example, with the fighter pilots, after they execute a maneuver particularly poorly

chances are the next attempt is going to be better, regardless of the feedback they receive.
chances are the next attempt is going to be better, regardless of the feedback they receive.

Similarly, after an especially successful display, chances are the next attempt is not
Similarly, after an especially successful display, chances are the next attempt is not

going to be as good.
going to be as good.

And that has nothing to do with the feedback and everything to do with the statistical
And that has nothing to do with the feedback and everything to do with the statistical

nature of our universe.
nature of our universe.

But we are hard wired to see patterns and causality everywhere, which is why the instructors
But we are hard wired to see patterns and causality everywhere, which is why the instructors

felt that positive feedback was detrimental and negative feedback is what works.
felt that positive feedback was detrimental and negative feedback is what works.

And this is really unfortunate, because that is the exact opposite of what well controlled
And this is really unfortunate, because that is the exact opposite of what well controlled

psychological studies show.
psychological studies show.

You know, I think it is really unfortunate that if you give negative feedback, chances
You know, I think it is really unfortunate that if you give negative feedback, chances

are you will be rewarded.
are you will be rewarded.

They will do better.
They will do better.

And if you give positive feedback, chances are you will be disappointed, because it is
And if you give positive feedback, chances are you will be disappointed, because it is

difficult to maintain that level of luck.
difficult to maintain that level of luck.

But that is the way our world is.
But that is the way our world is.

So think about that next time before you tell someone off.
So think about that next time before you tell someone off.

If you stay positive, it may just work out for the best in the long run.
If you stay positive, it may just work out for the best in the long run.

This video was inspired by the book Thinking Fast and Slow by Nobel prize winning economist
This video was inspired by the book Thinking Fast and Slow by Nobel prize winning economist

Daniel Kahneman.
Daniel Kahneman.

So that was the first time I heard of the Israeli fighter pilot training and really
So that was the first time I heard of the Israeli fighter pilot training and really

started thinking about regression to the mean.
started thinking about regression to the mean.

It was pretty awesome and I downloaded this book from Audible, so I was listening to it
It was pretty awesome and I downloaded this book from Audible, so I was listening to it

on my travels.
on my travels.

I am currently at the Perimeter Institute, which you can see has some beautiful black
I am currently at the Perimeter Institute, which you can see has some beautiful black

boards.
boards.

Now if you want to listen to this book, you can download it for free by going to Audible.com/Veritasium
Now if you want to listen to this book, you can download it for free by going to Audible.com/Veritasium

or you can listen to any other book of your choice for a one month free trial.
or you can listen to any other book of your choice for a one month free trial.

So thanks to Audible for supporting to me.
So thanks to Audible for supporting to me.

Thanks to Perimeter Institute for putting me up in this amazing location.
Thanks to Perimeter Institute for putting me up in this amazing location.

And I will see you next time with some theoretical physics ideas.
And I will see you next time with some theoretical physics ideas.

So stay tuned for that.
So stay tuned for that.