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Why eating ice cream is linked to shark attacks
Why are soda and ice cream each linked to violence? This article delivers the final word on what people mean by "correlation does not imply causation."
- Ice cream consumption is actually linked to shark attacks.
- But the relationship is correlative, not causal.
- It's pretty stunning how media outlets skip over this important detail.
Soda and ice cream are linked to violence. What the what? And people have concluded from data that smoking, chocolate, and curly fries are good for you. Why the when?
I'll explain -- but also go much further and show you… wait for it… that figuring out why such things are true doesn't even matter at all for driving decisions with data. Who the how? It's time for the "correlation does not imply causation" clarification proclamation moment of zen clarity. Let's do this!
Ice cream and shark attacks
Ice cream cone and a shark.
According to the data, ice cream consumption is linked to shark attacks. How the why? Well, maybe eating ice cream makes you taste better? So, you consume the ice cream and the shark consumes you. But the more accepted sharksplanation is that it's seasonal. It just so happens that, when it's warmer, more people are eating ice cream and also more people are swimming in the ocean.
That is to say that there's no causal relationship, in either direction -- neither of these things causes the other, even indirectly. Instead, they're both caused by a third factor. So the good news is that we've found a link, a connection, a correlation between these two factors in the data -- and that's valuable. The two are indeed predictive of one another. If we see ice cream sales increase, we can rightly ascertain a higher probability of shark attacks, and vice versa. But the bad news is that, when we discover such a correlation, oftentimes their common cause, some third factor, is just not in our data set at all. That data wasn't included, 'cause it was overlooked or perhaps it would be difficult or costly to collect. So we're stuck with a predictive correlation, but no definitive causal explanation as to why it is so.
Soda and violence
This headline about soda turning teens into killers is really something.
Now, soda also appears to be dangerous. In 2011, an economics professor and a health policy researcher went public with this as their research result. Among adolescents, they found, "a strong association between soft drinks and violence..." And they also wrote, "... drinking more than five cans of non-diet soft drinks per week was associated with a 9–15 percentage point increase in the probability of engaging in violent actions... There may be a direct cause-and-effect relationship, perhaps due to the sugar or caffeine content of soft drinks."Well, after that, a cacophony of media coverage erupted, with headlines like, "Soda Totally Turns Teens Into Killers." Then skeptics began to push back. Now, they didn't question the correlation between soda consumption and violence. Rather, they questioned the causal relationship. Ya see, you can conclude that there's a link, a connection, an association, a correlation between two factors without necessarily understanding why it is so. The "why" -- the explanation -- always involves causation: some insight as to how things influence or affect one another.
The criticism here is that you shouldn't conclude soda causes violence. Rather, it may be that diet is linked to socio-economic status. Lower income teens consume more junk food, including sodas, and poverty itself is a risk factor for teen violence. Now if that story is true, the causal links shown here -- like, the exact way in which poverty leads to violence -- could be pretty complex and somewhat multi-staged, but the point is that this is a plausible alternative explanation that doesn't have soda even indirectly causing violence, so it's unwarranted to sound the alarm about the dangers of soda.
Let me put it another way. Even if it's true that violent people drink more soda, there's no reason to fully believe that drinking soda will make you more violent. That would be like assuming that eating more ice cream will cause more shark attacks. Ice cream and soda may be bad for you, but not in that way.
Chocolate eaters are more slim
The operative word here is 'may'. Also, 'may not' would equally apply.
Anyway, now some great news: Some tempting vices are good for you, like chocolate, smoking, curly fries, and breakfast! ...is what people who presume causation say.
"More frequent chocolate intake is linked to a lower body mass index," according to three University of California medical and economics researchers who published this finding. Their writing states that this association "could be causal," since chocolate might lessen the depositing of fat.
And cue the media frenzy. A BBC headline announced, "Chocolate 'May Help Keep People Slim,'" and a Wall Street Journal video with "It appears to make you thin" in its caption kicks off with, "It doesn't make you fatter."
Now, I would say that people's passionate love for chocolate precipitates this wishful thinking and bold presumption of causation... but then again I can't really be sure what caused them to fudge it. It's funny 'cause it's true.
Correlation does not imply causation
Anyway, the discovery of a correlation between two items does not mean one causes the other, not even indirectly. It just doesn't necessarily tell us anything about any causal relationship. The hallways of universities and the chatrooms of the Internet echo with a frequent reminder of this utmost, dire warning:
"Correlation does not imply causation."
Statisticians absolutely scream this rule from the rooftops just as often as the popular press and big data hacks overlook it.
Now, looking at chocolate consumption and a lower body mass index, another plausible causal explanation would be that people reward themselves with chocolate when they lose weight. That is, lower weight leads to chocolate consumption, rather than the other way around.
Or, it could be that people just eat more chocolate because they weren't trying to lose weight in the first place because they were already thin.
Or another possibility is that poverty, which has been tied to higher weight, also makes chocolate less affordable, so people with a lower income weigh more on average and yet also eat less chocolate.
Or it could be some combination of all these different causal relationships. We don't know. The main point is, you gotta live in that uncertainty and avoid the temptation to presume a specific causal relationship when only correlation has been established. Adjust your brain to accept this lack of knowledge.
Smokers suffer less repetitive motion disorder
A seal smoking a pipe.
Another example: Smokers suffer less from repetitive motion disorder. An ergonomics consultant found that, among editors at a major metropolitan newspaper, those who smoked cigarettes were less likely to develop carpal tunnel syndrome. Could it be that this is a veritable health benefit of smoking? I don't think so! The consultant believes it was because smokers take more breaks.
That does seem like a more likely explanation to me, but remember that the correlation in the data in and of itself provides no evidence that one explanation is more likely than another. Scientifically establishing causation usually requires collecting data by way of an experimental setup that includes having a control group. But most of the data out there wasn't collected for science. Typical "big data" projects leverage the tremendous load of data that companies generate in the normal course of conducting business. Today's priceless explosion of data exists only as a fortunate side effect. Such data, also known as "found data," is like data from a typical survey or so-called "longitudinal" research in that it doesn't include any purposefully held-aside control group. So typical "big data" serves to establish correlations but not causation.
Curly fries and breakfast
These curly fries are looking delicious.
Guess what else. People who like "Curly Fries" on Facebook are more intelligent. So does that mean eating curly fries makes you smarter? Well, that would throw you for a loop. Instead, researchers believe it was just that a Facebook page for this fun food item happened to gain popularity among a group of relatively smart people.
And finally, men who eat breakfast face a lower risk of coronary heart disease. However, that doesn't necessarily mean breakfast deserves its reputation as the most important meal of the day. We can't conclude this connection results from the food itself being good for you. Instead, the researchers suggest that eating breakfast is a proxy for lifestyle -- if you're leading a busy, high-stressed life, you're more likely to skip breakfast and you're also subjected to a higher health risk. But, once again, that's largely just an intuitive hunch. As always, there are other plausible explanations.
Causality is only an avocational interest
Now, you may be asking, doesn't Dr. Data even care why these things are true? Isn't he at least curious? Well, yeah, for sure -- but it isn't my day job. People in the "real sciences" like physics, chemistry, and medical research have their work cut out for them. They have to figure out how the world works, why things happen the way they do. I don't envy them — 'cause we data scientists have it much easier. Most deployments of machine learning improve decision-making without scientifically investigating causal effects.
In fact, this point was once put quite bluntly by a chief analytics officer of the New York City mayor's office in a published interview — and this is a real: "Causation is for other people... it is very dicey... You know, we have real problems to solve. I can't dick around, frankly, thinking about other things like causation right now."
Ok, message received!
So, if a higher risk level is predicted for an individual, we don't necessarily need to understand why in order to take precautions accordingly. For example, screening men who skip breakfast for heart disease could be useful, even if we don't necessarily believe scrambled eggs and cornflakes are what make the difference to your health.
About the Dr. Data show
This article is based on a transcript from The Dr. Data Show.
This new web series breaks the mold for data science infotainment, captivating the planet with short webisodes that cover the very best of machine learning and predictive analytics. Click here to view more episodes and to sign up for future episodes of The Dr. Data Show.
A man's skeleton, found facedown with his hands bound, was unearthed near an ancient ceremonial circle during a high speed rail excavation project.
- A skeleton representing a man who was tossed face down into a ditch nearly 2,500 years ago with his hands bound in front of his hips was dug up during an excavation outside of London.
- The discovery was made during a high speed rail project that has been a bonanza for archaeology, as the area is home to more than 60 ancient sites along the planned route.
- An ornate grave of a high status individual from the Roman period and an ancient ceremonial circle were also discovered during the excavations.
Foul play?<p>A skeleton representing a man who was tossed face down into a ditch nearly 2,500 years ago with his hands bound in front of his hips was dug up during a high speed rail excavation.</p><p>The positioning of the remains have led archaeologists to suspect that the man may have been a victim of an ancient murder or execution. Though any bindings have since decomposed, his hands were positioned together and pinned under his pelvis. There was also no sign of a grave or coffin. </p><p>"He seems to have had his hands tied, and he was face-down in the bottom of the ditch," <a href="https://www.livescience.com/iron-age-murder-victim-england.html" target="_blank">said archaeologist Rachel Wood</a>, who led the excavation. "There are not many ways that you end up that way."</p><p>Currently, archaeologists are examining the skeleton to uncover more information about the circumstances of the man's death. Fragments of pottery found in the ditch may offer some clues as to exactly when the man died. </p><p>"If he was struck across the head with a heavy object, you could find a mark of that on the back of the skull," Wood said to <a href="https://www.livescience.com/iron-age-murder-victim-england.html" target="_blank">Live Science</a>. "If he was stabbed, you could find blade marks on the ribs. So we're hoping to find something like that, to tell us how he died."</p>
Other discoveries at Wellwick Farm<p>The grim discovery was made at Wellwick Farm near Wendover. That is about 15 miles north-west of the outskirts of London, where <a href="https://www.hs2.org.uk/building-hs2/hs2-green-corridor/" target="_blank">a tunnel</a> is going to be built as part of a HS2 high-speed rail project due to open between London and several northern cities sometime after 2028. The infrastructure project has been something of a bonanza for archaeology as the area is home to more than 60 ancient sites along the planned route that are now being excavated before construction begins. </p><p>The farm sits less than a mile away from the ancient highway <a href="http://web.stanford.edu/group/texttechnologies/cgi-bin/stanfordnottingham/places/?icknield" target="_blank">Icknield Way</a> that runs along the tops of the Chiltern Hills. The route (now mostly trails) has been used since prehistoric times. Evidence at Wellwick Farm indicates that from the Neolithic to the Medieval eras, humans have occupied the region for more than 4,000 years, making it a rich area for archaeological finds. </p><p>Wood and her colleagues found some evidence of an ancient village occupied from the late Bronze Age (more than 3,000 years ago) until the Roman Empire's invasion of southern England about 2,000 years ago. At the site were the remains of animal pens, pits for disposing food, and a roundhouse — a standard British dwelling during the Bronze Age constructed with a circular plan made of stone or wood topped with a conical thatched roof.</p>
Ceremonial burial site<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzUzMTk0Ni9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NDgwNTIyMX0.I49n1-j8WVhKjIZS_wVWZissnk3W1583yYXB7qaGtN8/img.jpg?width=1245&coordinates=0%2C82%2C0%2C83&height=700" id="44da7" class="rm-shortcode" data-rm-shortcode-id="46cfc8ca1c64fc404b32014542221275" data-rm-shortcode-name="rebelmouse-image" alt="top down view of coffin" data-width="1245" data-height="700" />
A high status burial in a lead-lined coffin dating back to Roman times.
Photo Credit: HS2<p>While these ancient people moved away from Wellwick Farm before the Romans invaded, a large portion of the area was still used for ritual burials for high-status members of society, Wood told Live Science. The ceremonial burial site included a circular ditch (about 60 feet across) at the center, and was a bit of a distance away from the ditch where the (suspected) murder victim was uncovered. Additionally, archaeologists found an ornately detailed grave near the sacred burial site that dates back to the Roman period, hundreds of years later when the original Bronze Age burial site would have been overgrown.</p><p>The newer grave from the Roman period encapsulated an adult skeleton contained in a lead-lined coffin. It's likely that the outer coffin had been made of wood that rotted away. Since it was clearly an ornate burial, the occupant of the grave was probably a person of high status who could afford such a lavish burial. However, according to Wood, no treasures or tokens had been discovered. </p>
Sacred timber circle<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzUzMTk0Ny9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2MDAwOTQ4Mn0.eVJAUcD0uBUkVMFuMOPSgH8EssGkfLf_MjwUv0zGCI8/img.jpg?width=1245&coordinates=0%2C149%2C0%2C149&height=700" id="9de6a" class="rm-shortcode" data-rm-shortcode-id="ee66520d470b26f5c055eaef0b95ec06" data-rm-shortcode-name="rebelmouse-image" alt="An aerial view of the sacred circular monument." data-width="1245" data-height="700" />
An aerial view of the sacred circular monument.
Photo Credit: HS2<p>One of the most compelling archaeological discoveries at Wellwick Farm are the indications of a huge ceremonial circle once circumscribed by timber posts lying south of the Bronze Age burial site. Though the wooden posts have rotted away, signs of the post holes remain. It's thought to date from the Neolithic period to 5,000 years ago, according to Wood.</p><p>This circle would have had a diameter stretching 210 feet across and consisted of two rings of hundreds of posts. There would have been an entry gap to the south-west. Five posts in the very center of the circle aligned with that same gap, which, according to Wood, appeared to have been in the direction of the rising sun on the day of the midwinter solstice. </p><p>Similar Neolithic timber circles have been discovered around Great Britain, such as one near <a href="https://bigthink.com/culture-religion/stonehenge-sarsens" target="_blank">Stonehenge</a> that is considered to date back to around the same time. </p>
Being skeptical isn't just about being contrarian. It's about asking the right questions of ourselves and others to gain understanding.
- It's not always easy to tell the difference between objective truth and what we believe to be true. Separating facts from opinions, according to skeptic Michael Shermer, theoretical physicist Lawrence Krauss, and others, requires research, self-reflection, and time.
- Recognizing your own biases and those of others, avoiding echo chambers, actively seeking out opposing voices, and asking smart, testable questions are a few of the ways that skepticism can be a useful tool for learning and growth.
- As Derren Brown points out, being "skeptical of skepticism" can also lead to interesting revelations and teach us new things about ourselves and our psychology.
New study suggests the placebo effect can be as powerful as microdosing LSD.
- New research from Imperial College London investigated the psychological effects of microdosing LSD in 191 volunteers.
- While microdosers experienced beneficial mental health effects, the placebo group performed statistically similar to those who took LSD.
- Researchers believe the expectation of a trip could produce some of the same sensations as actually ingesting psychedelics.
Psychedelics: The scientific renaissance of mind-altering drugs<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="92360c805fe66c11de38a75b0967f417"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/5T0LmbWROKY?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>For the study published in eLife, the team recruited 191 citizen cosmonauts to microdose either LSD or a placebo over the course of several weeks and note the psychological effects. Volunteers were already microdosing LSD, so there was no true control. Each volunteer was given instructions on creating their own low-dose gel capsules, some containing LSD, others not. Then they mixed the capsules in envelopes so they didn't know if they were taking the real thing or not.</p><p>The trial design was ingenious: each capsule featured a QR code that was scanned after the addition of ingredients but before they were placed in the envelope so that researchers knew what they were ingesting.</p><p>The problem: volunteers sourced their own LSD. Lack of quality control could have had a profound effect on the results. </p><p>The results: LSD microdosers reported feeling more mindful, satisfied with life, and better overall; they also noticed a reduction in feelings of paranoia. </p><p>The catch: the control group felt the same thing, with no statistical difference between the groups. </p><p>Lead author Balázs Szigeti comments on the findings: "This suggests that the improvements may not be due to the pharmacological action of the drug but can instead be explained by the placebo effect." </p>
Credit: Alexander / Adobe Stock<p>Psychedelics are notoriously difficult to control for given the intensity of the experience. Yet there is precedent for the above findings. A <a href="https://link.springer.com/article/10.1007/s00213-020-05464-5" target="_blank">2019 study</a> found that 61 percent of volunteers that took a placebo instead of psilocybin felt some psychedelic effects, with a few volunteers experiencing full-on trips.</p><p style="margin-left: 20px;">"Several stated that they saw the paintings on the walls 'move' or 'reshape' themselves, others felt 'heavy. . . as if gravity [had] a stronger hold', and one had a 'come down' before another 'wave' hit her."</p><p>The Imperial team believes the expectation of a trip might have been enough to produce similar results. Senior author David Erritzoe is excited for future studies on the topic, believing they tapped into a new wave of citizen science that could push forward our knowledge of psychedelic substances.</p><p style="margin-left: 20px;">"Accounting for the placebo effect is important when assessing trends such as the use of cannabidiol oils, fad diets or supplements where social pressure or users' expectations can lead to a strong placebo response. Self-blinding citizen science initiatives could be used as an inexpensive, initial screening tool before launching expensive clinical studies."</p><p>As investments into the psychedelics market explode, with one company <a href="https://www.bloomberg.com/news/articles/2021-03-03/thiel-backed-magic-mushroom-firm-atai-hits-2-billion-valuation" target="_blank">reaching a $2 billion valuation</a>, a recurring irony appears in the long arc of psychedelics and research: the power of our minds might be enough to feel greater life satisfaction and a deeper sense of mindfulness. If that's possible with a placebo, we have to question why the rush to create more pharmacology is necessary. </p><p>This is, mind you, a separate conversation over the role of psychedelics and rituals for group bonding. The function of group cohesion around consciousness-altering substances will continue to play an important role in many communities. </p><p>Of course, we should continue to explore the efficacy of psychedelics on anxiety, depression, suicidal ideation, PTSD, and addiction. <a href="https://bigthink.com/surprising-science/antidepressant-effects" target="_self">Pharmacological dependence</a> is a stain on the psychiatry industry. Whether or not psychedelics can be prescribed for daily use remains to be seen, but we know a moneyed interest is expecting a return on investment—the above company, ATAI Life Sciences, raised $157 million in its Series D round. </p><p>When it comes to wellbeing, some things money just can't buy. How we navigate the tricky terrain of mainstreaming psychedelics remains to be seen. </p><p>--</p><p><em>Stay in touch with Derek on <a href="http://www.twitter.com/derekberes" target="_blank">Twitter</a> and <a href="https://www.facebook.com/DerekBeresdotcom" target="_blank" rel="noopener noreferrer">Facebook</a>. His most recent book is</em> "<em><a href="https://www.amazon.com/gp/product/B08KRVMP2M?pf_rd_r=MDJW43337675SZ0X00FH&pf_rd_p=edaba0ee-c2fe-4124-9f5d-b31d6b1bfbee" target="_blank" rel="noopener noreferrer">Hero's Dose: The Case For Psychedelics in Ritual and Therapy</a>."</em></p>