Imma little blog

Flexible feather armor

By now many of you have probably seen the news reports of a scientific study in Nature supposedly showing that people actually become neurologically ‘adult’ at the age of 32 years old — not 25, as fans of the frontal lobe myleination theory of adulthood would have it, or 18, as the purely legalistic definition of adulthood would, or even 13 or 15, as many cultural rites of passage have variously held it to be.

No, now that some entirely exploratory research has discovered that the average, non-developmentally-disabled brain tends to enter a new phase of functioning and connectivity around the early 30s, we have a new random spot on the ground for pop scientists and those seeking to limit the rights of marginalized young people to draw a target around, and act like they were aiming for it the entire time.

In sum, researchers Alexa Mousley, Richard Bethlehem, Fang-Cheng Yeh, and Duncan Astle reviewed a large pool of nearly 4,000 MRI brain scan results, filtered exclusively for neurotypical participants, and found that, consistent with prior research on the subject, the density of neural connections tends to peak around age 30 for most people, as does topological efficiency (in essence, how long a distance neural information needs to travel across the brain, with shorter distances being more efficient).

Less reported on have been the study’s numerous other findings on neural changes that tend to occur with age, in particular the findings that neural modularity (how clearly neural nodes can be grouped into sub-sections) and efficiency between nearby nodes (also called local efficiency) peaks at around age 90.

Why having a brain that is hyper-connected and generally efficient is the marker of adulthood, but having a brain with highly specialized organization and really efficient individual connections is not is, of course, completely arbitrary. The only reason the news media isn’t treating brain modularity and local efficiency as hallmarks of maturity is because it would make too obviously a specious headline to claim that adulthood begins at 90.

Once you have allowed that certain people cannot be trusted to make their own decisions because of how their brains are structured, you open the door to limit any freedoms you dislike. All you have to do is pluck one random developmental trend from the sea of published neuroscientific data, and claim that anyone whose brain deviates from this milestone is a neurological ‘child’ who needs protection from their own autonomy.

But as any honest neuroscientist will tell you, the brain never finishes developing. Adulthood is a socially constructed category, not a biologically observable reality, and we all exist at some point along a continuum of development that is highly personal to us. Our endocrinology, ability to grow muscle, hormone production, metabolism, circadian rhythm, neural organization, neural efficiency, the presence of brain tumors or cysts — all of these things are changing within us at all times, and remain beautifully inconsistent over the course of our life span. We are not static. And we are all growing more disabled on a long enough timeline.

There is no single moment at which we can be said to be at our most adult — not without creating a definition of adulthood that is at once completely fleeting and ableist. Is it more adult to think quickly, or to make fewer errors than others? And if so, at what point do we start cutting off large swathes of people from the possibility of ever being a true adult, not just our elders and younger comrades, but every single person with a cognitive disability, brain fog, temporary injury, low blood sugar, or who just happens to live on the low end of the bell curve?

What’s the use in packaging a diverse collection of rights, social responsibilities, and modes of interacting under the single banner of ‘adulthood,’ anyway? Is an adult a person who can operate a vehicle? Take on a loan? Join the military? Understand every possible outcome of having sex or getting a medical procedure? Someone who has done an estimable deed for their community?

I can think of a lot of adults who have never done any of that. And I know a great many people who have taken on immense social responsibility when they were in a state of cognitive disability, or while they were children: they raised younger siblings, got drunken parents washed up and headed to work, drove a car full of their family members through a mud slide in the mountains, reported a predator sliding into their inbox, and registered dozens of adults to vote when they weren’t allowed to vote themselves.

By now many of you have probably seen the news reports of a scientific study in Nature supposedly showing that people actually become neurologically ‘adult’ at the age of 32 years old — not 25, as fans of the frontal lobe myleination theory of adulthood would have it, or 18, as the purely legalistic definition of adulthood would, or even 13 or 15, as many cultural rites of passage have variously held it to be.

No, now that some entirely exploratory research has discovered that the average, non-developmentally-disabled brain tends to enter a new phase of functioning and connectivity around the early 30s, we have a new random spot on the ground for pop scientists and those seeking to limit the rights of marginalized young people to draw a target around, and act like they were aiming for it the entire time.

In sum, researchers Alexa Mousley, Richard Bethlehem, Fang-Cheng Yeh, and Duncan Astle reviewed a large pool of nearly 4,000 MRI brain scan results, filtered exclusively for neurotypical participants, and found that, consistent with prior research on the subject, the density of neural connections tends to peak around age 30 for most people, as does topological efficiency (in essence, how long a distance neural information needs to travel across the brain, with shorter distances being more efficient).

Less reported on have been the study’s numerous other findings on neural changes that tend to occur with age, in particular the findings that neural modularity (how clearly neural nodes can be grouped into sub-sections) and efficiency between nearby nodes (also called local efficiency) peaks at around age 90.

Why having a brain that is hyper-connected and generally efficient is the marker of adulthood, but having a brain with highly specialized organization and really efficient individual connections is not is, of course, completely arbitrary. The only reason the news media isn’t treating brain modularity and local efficiency as hallmarks of maturity is because it would make too obviously a specious headline to claim that adulthood begins at 90.

Once you have allowed that certain people cannot be trusted to make their own decisions because of how their brains are structured, you open the door to limit any freedoms you dislike. All you have to do is pluck one random developmental trend from the sea of published neuroscientific data, and claim that anyone whose brain deviates from this milestone is a neurological ‘child’ who needs protection from their own autonomy.

But as any honest neuroscientist will tell you, the brain never finishes developing. Adulthood is a socially constructed category, not a biologically observable reality, and we all exist at some point along a continuum of development that is highly personal to us. Our endocrinology, ability to grow muscle, hormone production, metabolism, circadian rhythm, neural organization, neural efficiency, the presence of brain tumors or cysts — all of these things are changing within us at all times, and remain beautifully inconsistent over the course of our life span. We are not static. And we are all growing more disabled on a long enough timeline.

There is no single moment at which we can be said to be at our most adult — not without creating a definition of adulthood that is at once completely fleeting and ableist. Is it more adult to think quickly, or to make fewer errors than others? And if so, at what point do we start cutting off large swathes of people from the possibility of ever being a true adult, not just our elders and younger comrades, but every single person with a cognitive disability, brain fog, temporary injury, low blood sugar, or who just happens to live on the low end of the bell curve?

What’s the use in packaging a diverse collection of rights, social responsibilities, and modes of interacting under the single banner of ‘adulthood,’ anyway? Is an adult a person who can operate a vehicle? Take on a loan? Join the military? Understand every possible outcome of having sex or getting a medical procedure? Someone who has done an estimable deed for their community?

I can think of a lot of adults who have never done any of that. And I know a great many people who have taken on immense social responsibility when they were in a state of cognitive disability, or while they were children: they raised younger siblings, got drunken parents washed up and headed to work, drove a car full of their family members through a mud slide in the mountains, reported a predator sliding into their inbox, and registered dozens of adults to vote when they weren’t allowed to vote themselves.