“8 science-backed signs you’re smarter than average.” That’s the clickable headline of a nice infographic recently published by Business Insider. The blurb that introduces the graphic takes a solid stand on indefensible turf saying “research suggests that everything from your choice of pet to your height can influence your intelligence.” Ugh. This is like saying your shoe size can influence your age. And this kind of easily digestible takeaway tends to stick with people and interfere with decisions related to hiring, college admissions, and parenting. I’ll ignore for the moment my seemingly baseless assertion that this can influence people, and focus on pointing out why Business Insider is wrong and irresponsible; because this is the internet.
First, correlation is not causation. When two things happen together, it does not mean one caused the other. This common logical fallacy of questionable cause (also known as false cause) is pernicious because it comes so naturally and sometimes produces accurate — or at least useful — conclusions that have helped humans survive. For example I ate the bad berries, then I got sick; the bad berries made me sick. I heard a rustle in the bushes, then a velociraptor* jumped out; rustle equals danger. Unfortunately, equating correlation with causation still feels right to the human brain even where no causal connection exists. I killed, burned, and ate my goat, then the drought ended; goat sacrifice brings rain. I got my kid vaccinated and 3 months later, she was diagnosed with autism; vaccines cause autism**. As ice cream sales increase, drowning deaths also increase; ice cream consumption causes drowning.
Clearly when two things happen together, even when they happen together all the time, it does not mean one caused the other. Feel free to disagree; just know that you’re wrong. Now lets go through each of the “signs” in the infographic and point out why they fail to make you smarter than average.
Being the oldest child: BI provides no source for this study in the infographic, but it is probably this one from Petter Kristensen and Tor Bjerkedal published June 22, 2007 in Science and reported by the New York Times. I don’t see anything wrong with the study itself, but it’s important to understand what it means and what it doesn’t mean.
The study showed a significant positive correlation between being raised as the oldest child and higher IQ scores among male Norwegian military conscripts. The IQ benefit also showed up in second and third born siblings who had an older sibling die in childhood, so the source of the benefit is not biological. If the IQ benefit is not biological, then is must come from educational opportunities that are associated with being the oldest sibling in a Norwegian family. This suggests two things: (1) the IQ test used in this research tests educational factors, not just innate intelligence; and (2) because of cultural differences in family dynamics across nations, the IQ benefit won’t necessarily translate to other countries. And because cultures within a nation change over time, it may not apply to future generations even in Norway.
There’s nothing to suggest that the same IQ benefits cannot apply to females as well, but to the extent that different cultures may treat males and females differently within the family dynamic, the study loses another element of generalized predictive power. Therefore, the properly nuanced conclusion to be drawn is that there are educational advantages associated with being raised as the oldest child, at least in some cultures. Hmm, it feels less potent somehow than “being the oldest makes you smarter.
Music Lessons: The Moreno et al study (Moreno study) found improved verbal ability and executive function in children 4-6 years old after Music training as opposed to visual art training. This result is likely because of crossover between the brain systems that handle music and language. In fact, that is exactly what the Moreno study was designed to show; not improved intelligence. The Moreno study does not show that smart kids are more likely to take music lessons, or that kids who take music lessons are somehow made smarter. There is no evidence here that music lessons influence your intelligence — just evidence that music training also benefits language skills in children. Even then, this research did not show that the benefit persists into adulthood. So you might not be smarter than your peers from taking music lessons, but you might be able to convince them you are with your superior language skills.
You Don’t Smoke: The Weiser study found a correlation between smoking and IQ among Israeli military recruits. However the direction of causation, if any causation exists at all, is not clear. It might be that people who score lower in IQ tests tend to end up in social circles where smoking is common; they may end up smoking for cultural reasons rather than intelligence reasons. Or there might be a common cause of both low intelligence and drug use tendencies; perhaps the genes that make someone prone to addiction also interfere with intellectual development. Also, because we know that IQ tests measure both innate intelligence and education, it might just be that drug use negatively correlates with education. Finally, it could be that people with higher IQ are just less likely to start smoking. If this is the case, the fact that you don’t smoke is, at best, an indicator, not an influencer of intelligence. But who needed a scientific study to tell us that?
The bottom line is the Israeli study did not find any causation between smoking and intelligence. Although there seems to be a relationship between being smart and not smoking, there’s nothing here to indicate that quitting cigarettes will make you more intelligent. If you don’t smoke, don’t start. If you do, quit for health reasons; they’re all scientifically well-established.
You’re Thin: This one has sticking power because everyone can remember back to the scrawny kid in high school that got straight A’s. The Cournot research found a correlation between Body Mass Index (BMI) and word-list learning, a memory function. Although memory function probably plays into performance on IQ tests, the ability to remember word lists isn’t the kind of thing people typically consider a defining attribute of intelligence. More importantly BI failed to mention one critical finding of the study: “No significant association was found between changes in BMI and cognitive function” — People’s intelligence did not change when their BMI changed. This means that BMI is not influencing intelligence, but still leaves room for intelligence to influence BMI. Maybe smart people just enjoy intellectual stimulation more than they enjoy shoving food in their faces. More likely, people who are good at memorizing lists are better at remembering how much junk they just ate and eventually stop eating. Those with less capacity of mind; they get fat.
In the end, the best you can say based on this study is if you’re skinny, you’re less likely to forget something on your shopping list while at the grocery store. Maybe that’s because you’re hungry, but it has some value. But if you need to claim a superior ability to remember lists of words (because of your svelte frame) as one of your positive attributes, intelligence probably isn’t one of them.
You’re Left-Handed: Stanley Coren’s research included a set of experiments focused on the association between divergent thinking and left-handedness. It’s a shame BI didn’t give more details because the results are fascinating. First, we should clarify the meaning of divergent thinking. Divergent thinking is the cognitive process of approaching a problem by exploring many possible solutions. This is in opposition to convergent thinking, which follows a set of logical steps to arrive at a single well-established solution. Convergent thinking is what is typically measured in standardized test scores and IQ tests.
The fascinating part is that the correlation between a difference in divergent thinking and left-handedness only showed up in men. In addition, the more left-handed a subject was, the higher they tended to score on divergent thinking tests; this is a hallmark of a solid correlation. To seal the case for left-handedness, the high scores in divergent thinking were not associated with improved convergent thinking; the left-handers weren’t just doing better at divergent thinking because they were smarter. The take-away is that between two different-handed men of equal IQ (which measures convergent, not divergent thinking), the left-handed man will probably be more creative. So if you’re left-handed, you might be able to come up with lots of indicators that you’re more intelligent than average, but you won’t necessarily be more intelligent than average.
But the big point BI missed here is that one of the theories explaining why left handed men are more creative than their equally intelligent right-handed oppressors suggests there might be a brain function crossover between creativity and left-handedness similar to the music and language one above. If so, you might actually be able to improve your creativity by improving the dexterity of your left hand!
You’ve Used Recreational Drugs: The first alternate explanation you might think of here is that smart people tend to make more money, and therefore have more access to recreational drugs. But the results were corrected for socioeconomic background, so wealth is unlikely to explain increased drug use. What might explain the increased drug use is seeking stimulation. Other studies have suggested that stimulation seeking children benefit from enriched intellectual development. This suggests that the stimulation seeking behavior might be a common cause of both improved intelligence and attraction to recreational drug use.
Again, the direction of causality is important here. BI implies that recreational drug use will make you smarter, when there is no evidence that it does. However, what the research does suggest is that seeking stimulation can improve your cognitive development, at least as a child. Stimulation seeking here does not mean looking to get high, but rather a drive to seek novel experiences. It isn’t difficult to imagine how this behavior might lead to both improved cognitive development and increased recreational drug use later in life without recreational drug use itself providing any measurable benefit to intelligence. If you want to be smarter, don’t do drugs, seek new experiences. If you are already partaking in recreational drugs, you might be smarter than average but its also possible you’re dumber than average. Say no to drugs, kids***.
You Have a Cat: BI failed to provide a source for this one as well. This was the best I could do. The study asked 600 college students in Wisconsin about their pet preferences. Sixty percent said they preferred dogs and eleven percent reported preferring cats, while a third of participants said they liked or disliked both cats and dogs equally. It is important to note that participants did not report what pets they had, but rather what pets they prefer. So what the study really found was that people who self-reported a preference for cats, but don’t necessarily keep one as a pet, also tended score higher on an intelligence test than those that reported a preference for dogs.
If you think you’re smarter than average for owning a cat, your reasoning goes something like this. There were about 65 students in Wisconsin who said they like cats and scored higher than average on an intelligence test. I own a cat, so I’m probably smarter than average. Put that way, it starts to sound pretty stupid doesn’t it.
You’re Tall: The original study is here. It appears that Anne Case and Christina Paxson wanted to find a link between intelligence and height so they went looking for data to support that conclusion. The study finds a positive correlation between height and cognitive ability in adolescents and attaches that onto the well-known positive correlation between height and success in the labor market in adulthood. The problem is that in adolescents, there is no way to measure maturity outside of height and cognitive development. Even children of the same age can vary dramatically in maturity, height, and cognitive ability; not all children mature at the same rate. What this means is that both cognitive ability and height in teens may be attributable to maturity. If so, all you can really say is that kids who are more mature tend to be smarter. Well, duh. There’s no reason to conclude from this that adults who are taller are also smarter, because adults of differing heights are all fully mature.
If you want to measure a correlation between height and intelligence in adults who have entered the work force, there’s no better way to do that than by measuring height and intelligence in adults who have entered the work force. Case and Paxson came up short here. You cannot draw any useful conclusions about height and intelligence of adults from a group of non-adults where both height and intelligence are almost certainly attributable to a third cause: maturity.
What has been shown in numerous studies is that, on average, taller people make more money than shorter people. So if you’re making more money than the other guy, does it even matter if you’re also smarter? You’ve already won! Go play on your yacht and stop trying to fill your empty soul with scientifically unsupported conclusions that you’re superior in yet one more way. Gosh!
In conclusion there’s bad science and there’s bad science reporting. Bad science reporting is not peer reviewed by anyone who necessarily knows anything about how to science properly, so it’s likely that whatever science reporting you’re reading, they got it wrong, including this article right here. Be skeptical.
* I’m aware this never would have actually happened due to millions of years between the last velociraptors and the first humans.
** Vaccines do not cause autism. The science is pretty well settled on that. Jenny Mccarthy is neither a scientist nor a doctor, but she is a human, which is why she did a fallacy.
*** I’ve heard cocaine is amazing though. A friend told me. Also LSD is supposed to seriously open your mind. And ecstasy feels pretty great, I heard. I have lots of friends that are pretty smart.