The danger of mixing up causality and correlation: Ionica Smeets at TEDxDelft

Summary

In this enlightening talk, the speaker humorously warns against the perils of drawing incorrect causal conclusions from correlations. Using the example of ice-cream sales and drownings, the speaker illustrates the logical fallacy of mistaking correlation for causation. The discussion extends to serious examples, such as the supposed link between marriage and longevity, the impact of sleeping with lights on, and the relationship between self-esteem and academic performance. The speaker emphasizes the importance of understanding the underlying causes and mechanisms before asserting causality, leaving the audience with a memorable lesson to question correlations presented in everyday life.

Takeaways

• 🍦 The speaker humorously warns about a supposed correlation between ice-cream sales and drowning incidents to highlight the dangers of assuming causation from correlation.
• 🌞 The real underlying factor causing both ice-cream sales and drownings is nice weather, illustrating how correlations can be misleading without considering all variables.
• 🤔 The speaker emphasizes the importance of recognizing the logical fallacy of confusing correlation with causation, a common mistake even among smart people.
• 👨‍🎓 The example of married men living longer than single men is used to show how societal norms and pre-existing conditions can skew statistical interpretations.
• 🏠 The correlation between keeping lights on at night and children becoming short-sighted was initially misinterpreted, demonstrating the need for careful analysis before drawing conclusions.
• 👓 The corrected study on short-sightedness revealed a genetic link, teaching us that initial correlations can be overturned by further research.
• 🏫 A study from the '70s incorrectly suggested that high self-esteem leads to good grades, which was later debunked, showing the long-term impact of incorrect causation assumptions.
• 📚 The speaker advises skepticism towards claims of causation, urging the audience to question the 'why' and 'how' behind any asserted correlation.
• 🧠 The talk concludes with a call to remember the ice-cream example as a metaphor for the need to critically evaluate claims of causation in all aspects of life.
• 👏 The speaker receives applause, indicating the audience's appreciation for the engaging and informative discussion on correlation and causation.

Q & A

What is the main message of the speaker in the transcript?

The main message is to warn against the common logical mistake of assuming causality from correlation. The speaker uses various examples to illustrate how easily one can incorrectly conclude that one thing causes another simply because they are correlated.

Why does the speaker mention the correlation between ice-cream sales and drownings?

The speaker uses the correlation between ice-cream sales and drownings as a humorous example to show how a superficial connection can be misleading. The actual underlying factor is nice weather, which leads to both increased ice-cream sales and swimming, hence drownings.

What is the underlying factor that the speaker identifies in the ice-cream and drowning example?

The underlying factor identified by the speaker is nice weather. When the weather is nice, more people go swimming, which can lead to drownings, and also more people buy ice-cream.

How does the speaker refute the claim that marriage makes men live longer?

The speaker refutes the claim by explaining that it's not marriage that causes men to live longer, but rather that men who are healthy, rich, and well-educated, who already have a higher life expectancy, are more likely to get married.

What is the mistake made in the study about children sleeping with the lights on mentioned in the transcript?

The mistake made in the study was assuming that sleeping with the lights on caused short-sightedness. The corrected understanding is that short-sightedness is genetic, and parents who are short-sighted are more likely to leave the light on and have children who are also short-sighted.

What was the incorrect conclusion drawn from the study on children's self-esteem and academic performance in the '70s?

The incorrect conclusion was that high self-esteem in children leads to good grades. Later research showed that it's actually good grades that lead to higher self-esteem, not the other way around.

Why does the speaker emphasize the importance of understanding causality correctly?

The speaker emphasizes the importance of understanding causality correctly because incorrect assumptions can lead to misguided actions, policies, and beliefs, which can have serious consequences in various aspects of life, from personal decisions to public health.

What advice does the speaker give to the audience regarding correlations and causality?

The speaker advises the audience to be cautious when someone claims a causal relationship between two things. They should remember that correlation alone is not enough; one must understand the 'why' and 'how' behind the relationship to draw valid conclusions.

What is the final piece of advice the speaker gives to help the audience remember the lesson on causality?

The final piece of advice is to remember the ice-cream example whenever they encounter a claim of causality. This serves as a reminder to look for the underlying factors and not jump to conclusions based solely on correlation.

How does the speaker use humor in the transcript to make the discussion on correlations and causality more engaging?

The speaker uses humor by starting with the absurd example of ice-cream causing drownings and by including jokes about marriage and self-esteem. This light-hearted approach makes the topic more accessible and helps to illustrate the points being made.

Outlines

00:00

🍦 The Fallacy of Correlation and Causation

The speaker humorously begins by warning the audience about the dangers of ice-cream, suggesting a correlation between ice-cream sales and drowning incidents. Using a graph to illustrate the upward trend, they initially propose a ban on ice-cream. However, they quickly reveal the flaw in this reasoning, pointing out that nice weather is the underlying factor causing both the increase in ice-cream sales and drownings. The speaker emphasizes that jumping to conclusions about causality based on correlation is a common logical mistake. They aim to educate the audience to recognize and avoid this error, using the ice-cream example and other scenarios like the longevity of married men, which is actually a result of health and wealth rather than marriage itself.

05:02

👓 The Misinterpretation of Correlations in Research

The speaker continues by discussing serious research findings that have been misinterpreted due to the correlation-causation fallacy. They mention a 1999 study in 'Nature' that correlated children sleeping with lights on with a higher probability of becoming short-sighted. The media incorrectly concluded that using bed lamps caused harm to children, leading to parental anxiety. However, the study was later corrected to clarify that short-sightedness is genetic, and parents who are short-sighted are more likely to leave lights on and have short-sighted children. The speaker also addresses a study from the '70s that linked high self-esteem in children with good academic performance. The initial conclusion was that fostering self-esteem leads to better grades, but subsequent research showed the opposite: good grades lead to higher self-esteem. The speaker warns against accepting correlations as evidence of causality without understanding the underlying mechanisms, using examples like the potential misleading correlations between vaccines and autism or female bankers and the financial crisis.

Keywords

💡Correlation

Correlation refers to a statistical relationship between two variables, indicating that they change together in some way. In the video, the speaker uses the example of ice-cream sales and drownings to illustrate how a correlation does not imply causation. The speaker emphasizes that while there might be a correlation between the two, it is the nice weather that causes both an increase in ice-cream sales and drowning incidents, not the ice-cream itself.

💡Causation

Causation is the relationship between an action or event and another event that is the consequence of the first. The speaker clarifies the difference between correlation and causation, using various examples to show that just because two things occur together does not mean one causes the other. The video's theme revolves around the importance of understanding this distinction to avoid logical fallacies.

💡Logical Fallacy

A logical fallacy is a flaw in reasoning that leads to a false conclusion. The video discusses how jumping to conclusions about causation based on correlation is a common logical fallacy. The speaker aims to educate the audience on recognizing such fallacies to prevent them from making similar mistakes in reasoning.

💡Ice-cream Sales

Ice-cream sales are used as a metaphor in the video to represent a variable that correlates with another variable (drownings) but does not cause it. The speaker humorously suggests that one might conclude that ice-cream sales cause drownings due to a correlation, highlighting the absurdity of such a conclusion.

💡Drownings

Drownings are mentioned as a tragic event that correlates with ice-cream sales during nice weather. The speaker uses this correlation to point out that more people go swimming in good weather, leading to both an increase in ice-cream sales and drowning incidents, but it is the weather, not the ice-cream, that is the underlying cause.

💡Marriage

Marriage is discussed in the context of a study that suggests married men live longer than single men. The speaker challenges this conclusion by arguing that it is not marriage that causes men to live longer, but rather that healthier, wealthier, and better-educated men are more likely to get married, thus illustrating the importance of considering underlying factors.

💡Self-esteem

Self-esteem is explored in relation to academic performance. The speaker explains how a study initially suggested that high self-esteem in children leads to better grades. However, subsequent research indicated the opposite causality: good grades lead to higher self-esteem. This example is used to caution against assuming causation from correlation.

💡Genetics

Genetics is mentioned in the context of short-sightedness being a genetic trait. The speaker uses this to correct a misinterpretation from a study that initially linked children sleeping with the lights on to a higher probability of becoming short-sighted, when in fact, it was the genetic predisposition of the parents that was the underlying cause.

💡Media Misinterpretation

Media misinterpretation refers to the incorrect or sensationalized reporting of research findings by the media. The video discusses how a study's careful language about correlation was misinterpreted in the media, leading to the spread of misinformation about the effects of light exposure on children's eyesight.

💡Underlying Factor

An underlying factor is a variable that influences the relationship between two other variables but is not immediately apparent. The speaker uses the term to describe how factors such as nice weather or genetic predisposition can be the real cause behind observed correlations, such as the relationship between ice-cream sales and drownings or short-sightedness and bedroom lighting.

Highlights

Speaker warns about the dangers of drawing incorrect causality from correlations, using ice-cream and drownings as a humorous example.

Ice-cream sales and drownings both increase with nice weather, but ice-cream does not cause drownings.

The importance of recognizing the logical mistake of assuming causality from correlation.

Married men live longer than single men, but it's not marriage that causes the longer life.

Healthy, rich, well-educated men with higher life expectancy are more likely to get married.

A study in Nature in 1999 suggested a correlation between sleeping with lights on and short-sightedness in children.

The media misinterpreted the study, suggesting that leaving lights on is harmful to children.

The study had to be corrected; short-sightedness is genetic, not caused by lights on in the bedroom.

Parents who are short-sighted are more likely to leave lights on and have short-sighted children.

In the '70s, a strong link was found between kids' self-esteem and academic performance.

The initial conclusion was that high self-esteem leads to good grades, which was later debunked.

Good grades actually cause high self-esteem, not the other way around.

Raising kids with high self-confidence without achievement can lead to low self-esteem and failure.

The speaker emphasizes the need to understand why and how before concluding causality from correlation.

Examples given include vaccines and autism, and female bankers and the financial crisis, cautioning against correlation mistakes.

The speaker concludes with the advice to remember the ice-cream example when evaluating causal claims.

Transcripts

Transcriber: Emil-Lorant Cocian Reviewer: Ariana Bleau Lugo

Welcome. I came here today to warn you

about the dangers of ice-cream.

You may not be aware of this,

but these innocent looking cones full of sweetness

are one of the major causes of drownings.

And I've got the numbers to prove it.

So, if you plot a graph of the number of ice-creams that are sold,

and you compare it with the number of drownings,

you can see there is clearly an upwards trend,

and I think it's very safe to conclude from this

that we should ban ice-cream because it's very dangerous.

(Laughter) (Applause)

Since you're all smart people,

you've probably figured out

there's something wrong with my example.

What's really happening here is, of course,

that there is an underlying factor,

which is nice weather, you might have guessed it.

And if the weather is nice,

more people will go out swimming,

and unfortunately drown, and at the same time,

more people will buy ice-cream.

And it's not the ice-cream that's causing the drownings.

And here it's really easy to see that

there is something wrong,

but jumping to an incorrect conclusion about causality

when you see a correlation

is the most often made logical mistake.

And today my goal is to make sure that

in the future you can recognize this mistake.

And I really hope you can avoid making it

in the future for yourselves.

And I'll do this by just giving some famous examples.

And the first one is really rather innocent.

The fact is that

married men live longer than single men.

If you look at the statistics, you see that

this is really happening.

And women's magazines, they like to conclude from this

that marriage is very healthy for men,

because it makes them live longer.

Well, a friend of mine, he likes to joke that

marriage mainly makes life seem longer,

but -- (Laughter) --

that's because his wife is --

(Cheers) (Applause)

But so, can anyone guess what's going on here?

Because there is a causal relation,

but it's the other way around.

The fact is that men who are healthy,

and rich, and well educated,

and have a much higher life expectancy,

these are the men that are much more likely

to find a wife -- that's the way women are --

and the guys who have a very low life expectancy,

so they're unhealthy and poor,

they are not as likely to get married.

So it's the high life expectancy

that is causing the marriage,

not the other way around.

Well, and this, of course, you know,

it's not so serious, no one will get married

just because he read this.

So let's move to a more serious example.

It was also more serious research.

In Nature there was a study in 1999 that showed

that young kids who sleep with the lights on,

that they have a much higher probability

of becoming short-sighted later in life.

But the researchers, they were smart,

and they wrote very careful

that they had found a correlation,

and they didn't know how the causal relation might work,

but just to be sure they advised all parents

to turn off the lights at night.

And in the popular media this became that

bed lamps were night abuse, children's abuse,

and that it was very bad

if parents used lamps in the bedroom.

And many parents were worried.

I can imagine, if this would have happened

when my son was sleeping with the lights on,

I would had felt really bad.

But luckily, the article had to be corrected

the next week, and maybe some of you can guess,

and if there are biologists in the audience, they know.

Short-sightedness is genetic.

And so, it's parents who are short-sighted.

And those are the parents who like to

leave the light on in the bedroom,

and they also are the parents

who have short-sighted kids.

So again, a simple mistake, easy to make.

Then, what is I think the worst example I know --

I know many of them,

I see at least one of these

in the newspapers every week.

But this is a classic one: in the '70s,

researchers found that there is a very strong link

between kids who do well in school, get good grades,

and kids who have a high self-esteem.

And they concluded from this

that it's very important to make sure that

young kids are, you know, raised

to be confident and proud of themselves,

because if their self-esteem is high,

the good results will follow.

And this forethought was told to parents,

especially in the US, for generations,

that just make sure that your kid is proud and confident,

then all will turn out well.

And many years later, someone did another study

just to see in which

direction the cause was working.

And they found that it was in the opposite direction.

So the good grades were causing the self-esteem,

and self-esteem wasn't causing good grades.

And it was even worse.

So kids who are raised just to have high self-confidence,

and not excel at anything --

it can be sports or music,

doesn't have to be school --

the kids who are just proud of themselves,

and then fail at everything,

in the end they will have a very low self-esteem,

and not be able to make anything of their life.

So this was a very serious correlation mistake.

And what I want for today is for you

to remember that the next time

someone wants to prove that there is a causal relation

between something and something else --

it can be anything, it can be vaccines and autism,

it can be female bankers and the financial crisis,

and if they -- (Laughter) -- point out to you

that there is a very strong relation,

remember that it's not enough to have a correlation.

It gives a very good hint of what might be happening,

but before you can conclude that one thing causes something else,

you need to know why it does and how it does.

So, when in doubt, just remember the ice-cream.

Thank you very much.

(Applause)