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Why is 18 the age of adulthood if the brain can take 30 years to mature?
Neuroscience research suggests it might be time to rethink our ideas about when exactly a child becomes an adult.
- Research suggests that most human brains take about 25 years to develop, though these rates can vary among men and women, and among individuals.
- Although the human brain matures in size during adolescence, important developments within the prefrontal cortex and other regions still take place well into one's 20s.
- The findings raise complex ethical questions about the way our criminal justice systems punishes criminals in their late teens and early 20s.
At what age does someone become an adult? Many might say that the 18th birthday marks the transition from childhood to adulthood. After all, that's the age at which people can typically join the military and become fully independent in the eyes of the law.
But in light of research showing our brains develop gradually over the course of several decades, and at different paces among individuals, should we start rethinking how we categorize children and adults?
"There isn't a childhood and then an adulthood," Peter Jones, who works as part of the epiCentre group at Cambridge University, told the BBC. "People are on a pathway, they're on a trajectory."
The prefrontal cortex, cerebellum and reward systems
One key part of that trajectory is the development of the prefrontal cortex, a significant part of the brain, in terms of social interactions, that affects how we regulate emotions, control impulsive behavior, assess risk and make long-term plans. Also important are the brain's reward systems, which are especially excitable during adolescence. But these parts of the brain don't stop growing at age 18. In fact, research shows that it can take more than 25 years for them to reach maturity.
The cerebellum also affects our cognitive maturity. But unlike the prefrontal cortex, the development of the cerebellum appears to depend largely on environment, as Dr. Jay Giedd, chair of child psychiatry at Rady Children's Hospital-San Diego, told PBS:
"Identical twins' cerebellum are no more alike than non-identical twins. So we think this part of the brain is very susceptible to the environment. And interestingly, it's a part of the brain that changes most during the teen years. This part of the brain has not finished growing well into the early 20s, even. The cerebellum used to be thought to be involved in the coordination of our muscles. So if your cerebellum is working well, you were graceful, a good dancer, a good athlete.
But we now know it's also involved in coordination of our cognitive processes, our thinking processes. Just like one can be physically clumsy, one can be kind of mentally clumsy. And this ability to smooth out all the different intellectual processes to navigate the complicated social life of the teen and to get through these things smoothly and gracefully instead of lurching. . . seems to be a function of the cerebellum."
The effects environment can bring upon the cerebellum even further complicate the question when does a child become an adult, considering the answer might depend on the kind of childhood an individual experienced.
Adulthood and the criminal justice system
These factors of cognitive develop raise many philosophical questions, but perhaps none are as important as those related to how we punish criminal, especially among young men, whose brains develop an average of two years later than women.
"The preponderance of young men engaging in these deadly, evil, and stupid acts of violence may be a result of brains that have yet to fully developed," Howard Forman, an assistant professor of psychiatry at Albert Einstein College of Medicine, told Business Insider.
So, does that mean young criminals — say, 19- to 25-year-olds — should be receive the same punishment as a 35-year-old who commits the same crime? Both criminals would still be guilty, but each might not necessarily deserve the same punishment, as Laurence Steinberg, a professor of psychology at Temple University, told Newsweek.
"It's not about guilt or innocence... The question is, 'How culpable are they, and how do we punish them?'"
After all, most countries have separate juvenile justice systems to deal with children who commit crimes. These separate systems are predicated on the idea that there ought to be a spectrum of culpability that accounts for a criminal's age. So, if we assume that the importance of age in the eyes of the justice system is based largely on cognitive differences between children and adults, then why shouldn't that culpability spectrum be modified to better match the science, which clearly shows that 18 is not the age at which the brain is fully matured?
Whatever the answer, society clearly needs some definition of adulthood in order to be able to differentiate between children and adults in order to function smoothly, as Jones suggested to the BBC.
"I guess systems like the education system, the health system and the legal system make it convenient for themselves by having definitions."
But that doesn't mean these definitions make sense outside of a legal context.
"What we're really saying is that to have a definition of when you move from childhood to adulthood looks increasingly absurd," he said. "It's a much more nuanced transition that takes place over three decades."
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Andy Samberg and Cristin Milioti get stuck in an infinite wedding time loop.
- Two wedding guests discover they're trapped in an infinite time loop, waking up in Palm Springs over and over and over.
- As the reality of their situation sets in, Nyles and Sarah decide to enjoy the repetitive awakenings.
- The film is perfectly timed for a world sheltering at home during a pandemic.
Richard Feynman once asked a silly question. Two MIT students just answered it.
Here's a fun experiment to try. Go to your pantry and see if you have a box of spaghetti. If you do, take out a noodle. Grab both ends of it and bend it until it breaks in half. How many pieces did it break into? If you got two large pieces and at least one small piece you're not alone.
But science loves a good challenge<p>The mystery remained unsolved until 2005, when French scientists <a href="http://www.lmm.jussieu.fr/~audoly/" target="_blank">Basile Audoly</a> and <a href="http://www.lmm.jussieu.fr/~neukirch/" target="_blank">Sebastien Neukirch </a>won an <a href="https://www.improbable.com/ig/" target="_blank">Ig Nobel Prize</a>, an award given to scientists for real work which is of a less serious nature than the discoveries that win Nobel prizes, for finally determining why this happens. <a href="http://www.lmm.jussieu.fr/spaghetti/audoly_neukirch_fragmentation.pdf" target="_blank">Their paper describing the effect is wonderfully funny to read</a>, as it takes such a banal issue so seriously. </p><p>They demonstrated that when a rod is bent past a certain point, such as when spaghetti is snapped in half by bending it at the ends, a "snapback effect" is created. This causes energy to reverberate from the initial break to other parts of the rod, often leading to a second break elsewhere.</p><p>While this settled the issue of <em>why </em>spaghetti noodles break into three or more pieces, it didn't establish if they always had to break this way. The question of if the snapback could be regulated remained unsettled.</p>
Physicists, being themselves, immediately wanted to try and break pasta into two pieces using this info<p><a href="https://roheiss.wordpress.com/fun/" target="_blank">Ronald Heisser</a> and <a href="https://math.mit.edu/directory/profile.php?pid=1787" target="_blank">Vishal Patil</a>, two graduate students currently at Cornell and MIT respectively, read about Feynman's night of noodle snapping in class and were inspired to try and find what could be done to make sure the pasta always broke in two.</p><p><a href="http://news.mit.edu/2018/mit-mathematicians-solve-age-old-spaghetti-mystery-0813" target="_blank">By placing the noodles in a special machine</a> built for the task and recording the bending with a high-powered camera, the young scientists were able to observe in extreme detail exactly what each change in their snapping method did to the pasta. After breaking more than 500 noodles, they found the solution.</p>
The apparatus the MIT researchers built specifically for the task of snapping hundreds of spaghetti sticks.
(Courtesy of the researchers)
What possible application could this have?<p>The snapback effect is not limited to uncooked pasta noodles and can be applied to rods of all sorts. The discovery of how to cleanly break them in two could be applied to future engineering projects.</p><p>Likewise, knowing how things fragment and fail is always handy to know when you're trying to build things. Carbon Nanotubes, <a href="https://bigthink.com/ideafeed/carbon-nanotube-space-elevator" target="_self">super strong cylinders often hailed as the building material of the future</a>, are also rods which can be better understood thanks to this odd experiment.</p><p>Sometimes big discoveries can be inspired by silly questions. If it hadn't been for Richard Feynman bending noodles seventy years ago, we wouldn't know what we know now about how energy is dispersed through rods and how to control their fracturing. While not all silly questions will lead to such a significant discovery, they can all help us learn.</p>
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- "The evidence is that about 70 percent of people are not engaged in what they do all day long, and about 18 percent of people are repulsed," London Business School professor Dan Cable says, calling the current state of work unhappiness an epidemic. In this video, he and other big thinkers consider what it means to find meaning in your work, discuss the parts of the brain that fuel creativity, and share strategies for reassessing your relationship to your job.
- Author James Citrin offers a career triangle model that sees work as a balance of three forces: job satisfaction, money, and lifestyle. While it is possible to have all three, Citrin says that they are not always possible at the same time, especially not early on in your career.
The planet is making a lot less noise during lockdown.
- A team of researchers found that Earth's vibrations were down 50 percent between March and May.
- This is the quietest period of human-generated seismic noise in recorded history.
- The researchers believe this helps distinguish between natural vibrations and human-created vibrations.
Earth is quieter as coronavirus lockdowns reduce seismic vibration<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="cc871d5d88a79ecc6605ce488c26a7c1"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/_yFF2MziwPA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>The team investigated seismic data from a global network of 268 stations spread out across 117 countries. As lockdown measures in different regions began, they tracked the drop in vibrations. Singapore and New York City recorded some of the biggest drops, though even Germany's Black Forest—famous for its association with the Brothers Grimm fairy tales—went quieter than usual.</p><p>The researchers also relied on citizen-owned seismometers in Cornwall and Boston, which recorded a 20 percent reduction from relatively quiet stretches in these college towns, such as during school holidays. </p><p>The environmental impact of lockdown has been dramatic. Indian skylines are notoriously grey. This <a href="https://www.axios.com/coronavirus-lockdown-pollution-drops-india-156b4f1d-160b-44d9-885a-148960b9e469.html" target="_blank">collection of photos</a> shows how quickly nature recovers when humans limit travel and industry. Such photographs also make you wonder why we cannot control emissions to begin with, now that we know the stakes. </p><p>Lead author, Dr Thomas Lecocq, says their research could help seismologists suss out the difference between human-created vibrations and natural vibrations, potentially resulting in longer lead times when natural disasters are set to strike. </p><p style="margin-left: 20px;">"With increasing urbanisation and growing global populations, more people will be living in geologically hazardous areas. It will therefore become more important than ever to differentiate between natural and human-caused noise so that we can 'listen in' and better monitor the ground movements beneath our feet. This study could help to kick-start this new field of study."</p>
Stray puppies play in an abandoned, partially-completed cooling tower inside the exclusion zone at the Chernobyl nuclear power plant on August 18, 2017 near Chornobyl, Ukraine.
Photo by Sean Gallup/Getty Images<p>The Earth is much stronger than us; humans are its products. In his 2007 book, "The World Without Us," Alan Weisman details just how quickly nature recovers from our insults. Chernobyl offers a <a href="http://www.bbc.com/earth/story/20160421-the-chernobyl-exclusion-zone-is-arguably-a-nature-reserve" target="_blank">real-world example</a>, while <a href="https://www.scientificamerican.com/article/even-if-injection-of-fracking-wastewater-stops-quakes-wont/" target="_blank">earthquakes caused by fracking-related wastewater injection</a> in Oklahoma are evidence of how much damage human "vibrations" cause.</p><p>Weisman's poetic homage imagines a symbiotic relationship with nature. This relationship depends on our cooperation, however. Weisman knows we aren't long for this world, nor is this world long for this universe: in just five billion years, give or take, Earth will implode. We all live on borrowed time. How we live during that time defines our character. </p><p>While he strikes a hopeful tone, Weisman knows nature will eventually have her way with us.</p><p style="margin-left: 20px;">"After we're gone, nature's revenge for our smug, mechanized superiority arrives waterborne. It starts with wood-frame construction, the most widely used residential building technique in the developed world. It begins on the roof, probably asphalt, or slate shingle, warranted to last two or three decades—but that warranty doesn't count around the chimney, where the first leak occurs." </p><p>The play-by-play of our demise continues, though Weisman offers plenty of proactive advice. The question is, will we be able to live up to it? Sadly, nothing in modern society hints at the possibility. </p><p>The only way we seem willing to pause our relentless pursuit of "progress" is when we're forced to do so, as in the current pandemic. The results, as the team in Belgium shows, are measurable. Whether or not we heed the call to slow our impact remains to be seen. Given precedent, it's unlikely, though as Weisman concludes, one can always dream. </p><p>--</p><p><em>Stay in touch with Derek on <a href="http://www.twitter.com/derekberes" target="_blank">Twitter</a>, <a href="https://www.facebook.com/DerekBeresdotcom" target="_blank">Facebook</a> and <a href="https://derekberes.substack.com/" target="_blank">Substack</a>. His next book is</em> "<em>Hero's Dose: The Case For Psychedelics in Ritual and Therapy."</em></p>