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Three ways your environment affects your intelligence

You can be born with good genes and study hard and still not meet your potential. Your environment has a lot to do with how smart you are.

  • Euthenics refers to the practice of improving humanity's environment in order to maximize its potential.
  • Throughout history, we've tweaked our surroundings in such a way as to directly enhance our intelligence.
  • These examples underscore the importance of environmental regulation and policies; otherwise, we might just be throwing away our potential.


Every few years, researchers administer IQ tests to a sample of test subjects, take the median score, and declare that to be the new "100," the score that means you're of perfectly average intelligence. This begs the question: Why do they need to update the average score? Simply put, we've been getting smarter. Every time the test is re-administered, the median score has almost always gone up. In fact, if we were to administer today's IQ tests to people from 100 years ago, they'd score somewhere around a 70; researchers estimate that our IQ scores jump about 3 points every decade. This is called the Flynn effect, named after the researcher who discovered it.

There are several proposed reasons for the Flynn effect. It could be that more people are attending school than they were before or that we do a better job of teaching students the skills directly related to IQ tests. These may be true, but there is one domain that has unquestionably increased our smarts: euthenics.

Where eugenics deals with improving humanity by selectively breeding allegedly "superior" groups of people — an idea that would ultimately sow considerable discord and decidedly not improve humanity's condition — euthenics focuses on improving humanity by improving our environment. Here are three examples of how tweaking our environment can make us smarter.

The US Government tinkers with salt

In the early 20th century, people living in the Great Lakes and Pacific Northwest regions were particularly susceptible to acquiring goiters, which are swollen lumps in the neck associated with a dysfunctional thyroid gland. David Murray Cowie, a professor of pediatrics, knew that this was due to iodine deficiency, a critical micronutrient that the thyroid needs in order for it to function properly. Cowie also knew that the Swiss incorporated sodium iodide in table salt to prevent this condition, so he persuaded the US government to implement the practice as well.

In the fall of 1924, the Morton Salt Company began distributing iodized salt at a national level. As expected, the number of goiters dropped precipitously.

Nearly 100 years later, researchers discovered that introducing iodized salt had some significant ancillary benefits as well. In iodine-deficient regions, IQ scores jumped by 15 points, and they increased by 3 points nationally. What's more, incomes in those iodine-deficient regions grew by 11 percent. How did this happen?

Iodine is easiest to gain from seafood and seaweeds, but it can also be gained from plants and animals so long as those plants and animals were raised on soil rich in iodine. In the Great Lakes and Pacific Northwest regions, floods and ancient glaciers had scrubbed all the iodine from the soil. This made goiters more common, but it also had a major impact on pregnant women. If a pregnant woman has an iodine deficiency (and therefore a dysfunctional thyroid gland), their child will be mentally impaired. A huge chunk of the US population had grown up with iodine-deficient mothers, negatively impacting their potential.

Making gasoline even more toxic

Photo: David Brodbeck via Flickr

In 1922, GM discovered that a chemical called tetraethyl lead worked fantastically as an anti-knock compound in automobiles — essentially, it prevented the early combustion of fuel. Ethanol would have worked just as well, but this substance could not be patented despite being considerably less toxic than lead. So, GM worked with oil companies to introduce lead into gasoline rather than the safer but less profitable ethanol. GM, Du Pont, and the general public were all aware that tetraethyl lead was poisonous. Rather than refer to this additive by its true name, they called it "ethyl."

Unfortunately, leaded gasoline remained a fact of life far after the public became aware of it. It was only in the mid-1970s with the passage of the Clean Air Act that its use was banned. And once we scrubbed the lead out of our gasoline, the terrible impact of this decades-long poisoning became clear.

The generation born after the Clean Air Act gained 6 points in their IQ scores. What's more, researchers argue that kids who grew up during the period between lead's introduction to gasoline in the 1920s and its elimination in the 1970s drove up to 90 percent of the variation in violent crime. Crime in cities like Los Angeles and New York reached dizzying heights in the '80s and '90s and then dropped continuously as the last leaded generation died, became incarcerated, or escaped their criminal lifestyle. Politicians were eager to attribute this to police practices, such as the "broken windows" theory of law enforcement, but some researchers assert that it had more to do with the smarter, healthier, and better-adjusted crop of citizens who grew up in a lead-free environment.

The link between smog and brain fog

While the previous items on this list discussed things that we have done, humanity still has a long way to go before pollution is significantly reduced. Every year, the State of Global Air project releases a report [PDF] assessing the severity of air pollution around the world. The most recent report found that 92 percent of the world's population is living in an area that exceeds healthy guidelines for small, particulate air pollution as set out by the World Health Organization. Not only is this bad for local ecosystems, climate change, and the human body, air pollution has been linked to major decrements in intelligence.

One study, for instance, analyzed a dataset of nearly 32,000 observations of standardized test scores and the daily air pollution index throughout China. The researchers found that the longer a study participant was exposed to high levels of pollution, the more their intelligence dropped. In particular, linguistic ability was affected the most, and men were more affected than women. Overall, the average effect of pollution reduced the study participants' intelligence to a similar degree as missing a year of school, roughly the equivalent of 5 IQ points.

Small particles from air pollution enter the body through the lungs, and from there, they travel throughout the body, including to the brain. The researchers from this study speculated that these particles were likely inflaming the brain and thereby damaging its white matter at an accelerated rate.

We like to think that our intellect is a resource we're born with, one that we can exercise or let go to waste. This isn't exactly true. Intelligence is a dynamic phenomenon that depends on the quality of our environment to a considerable degree. That's why smart regulations and policies are important. Without them, we might not get smart enough to implement them in the first place.


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Human brains remember certain words more easily than others

A study of the manner in which memory works turns up a surprising thing.

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  • Researchers have found that some basic words appear to be more memorable than others.
  • Some faces are also easier to commit to memory.
  • Scientists suggest that these words serve as semantic bridges when the brain is searching for a memory.

Cognitive psychologist Weizhen Xie (Zane) of the NIH's National Institute of Neurological Disorders and Stroke (NINDS) works with people who have intractable epilepsy, a form of the disorder that can't be controlled with medications. During research into the brain activity of patients, he and his colleagues discovered something odd about human memory: It appears that certain basic words are consistently more memorable than other basic words.

The research is published in Nature Human Behaviour.

An odd find

Image source: Tsekhmister/Shutterstock

Xie's team was re-analyzing memory tests of 30 epilepsy patients undertaken by Kareem Zaghloul of NINDS.

"Our goal is to find and eliminate the source of these harmful and debilitating seizures," Zaghloul said. "The monitoring period also provides a rare opportunity to record the neural activity that controls other parts of our lives. With the help of these patient volunteers we have been able to uncover some of the blueprints behind our memories."

Specifically, the participants were shown word pairs, such as "hand" and "apple." To better understand how the brain might remember such pairings, after a brief interval, participants were supplied one of the two words and asked to recall the other. Of the 300 words used in the tests, five of them proved to be five times more likely to be recalled: pig, tank, doll, pond, and door.

The scientists were perplexed that these words were so much more memorable than words like "cat," "street," "stair," "couch," and "cloud."

Intrigued, the researchers looked at a second data source from a word test taken by 2,623 healthy individuals via Amazon's Mechanical Turk and found essentially the same thing.

"We saw that some things — in this case, words — may be inherently easier for our brains to recall than others," Zaghloul said. That the Mechanical Turk results were so similar may "provide the strongest evidence to date that what we discovered about how the brain controls memory in this set of patients may also be true for people outside of the study."

Why understanding memory matters

person holding missing piece from human head puzzle

Image source: Orawan Pattarawimonchai/Shutterstock

"Our memories play a fundamental role in who we are and how our brains work," Xie said. "However, one of the biggest challenges of studying memory is that people often remember the same things in different ways, making it difficult for researchers to compare people's performances on memory tests." He added that the search for some kind of unified theory of memory has been going on for over a century.

If a comprehensive understanding of the way memory works can be developed, the researchers say that "we can predict what people should remember in advance and understand how our brains do this, then we might be able to develop better ways to evaluate someone's overall brain health."

Party chat

Image source: joob_in/Shutterstock

Xie's interest in this was piqued during a conversation with Wilma Bainbridge of University of Chicago at a Christmas party a couple of years ago. Bainbridge was, at the time, wrapping up a study of 1,000 volunteers that suggested certain faces are universally more memorable than others.

Bainbridge recalls, "Our exciting finding is that there are some images of people or places that are inherently memorable for all people, even though we have each seen different things in our lives. And if image memorability is so powerful, this means we can know in advance what people are likely to remember or forget."

spinning 3D model of a brain

Temporal lobes

Image source: Anatomography/Wikimedia

At first, the scientists suspected that the memorable words and faces were simply recalled more frequently and were thus easier to recall. They envisioned them as being akin to "highly trafficked spots connected to smaller spots representing the less memorable words." They developed a modeling program based on word frequencies found in books, new articles, and Wikipedia pages. Unfortunately, the model was unable to predict or duplicate the results they saw in their clinical experiments.

Eventually, the researchers came to suspect that the memorability of certain words was linked to the frequency with which the brain used them as semantic links between other memories, making them often-visited hubs in individuals's memory networks, and therefore places the brain jumped to early and often when retrieving memories. This idea was supported by observed activity in participants' anterior temporal lobe, a language center.

In epilepsy patients, these words were so frequently recalled that subjects often shouted them out even when they were incorrect responses to word-pair inquiries.

Seek, find

Modern search engines no longer simply look for raw words when resolving an inquiry: They also look for semantic — contextual and meaning — connections so that the results they present may better anticipate what it is you're looking for. Xie suggests something similar may be happening in the brain: "You know when you type words into a search engine, and it shows you a list of highly relevant guesses? It feels like the search engine is reading your mind. Well, our results suggest that the brains of the subjects in this study did something similar when they tried to recall a paired word, and we think that this may happen when we remember many of our past experiences."

He also notes that it may one day be possible to leverage individuals' apparently wired-in knowledge of their language as a fixed point against which to assess the health of their memory and brain.

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