Thirty is an age that causes consternation for many 20-somethings. Life gets super serious at age 30, the narrative goes, with career changes, gluten and lactose intolerance and the inability to stay awake past midnight, not to mention the burning matter of “settling down.”

*dun dun dun*

But in reality, let’s be honest, your 30s aren’t something to fear. They’re when things start to get really good, especially when comes to relationships.

The reason is rooted in science. The cerebellum, directly connected to how we think, feel, look, and remember, has not finished growing well into the early 20s. Even into our 30s our brains are changing, getting rid of the unused connections and strengthening those that remain.

As our brains sharpen, our personalities settle.

Research has shown that between the ages of 18 and 30, people become more neurotic, introverted and possibly less open to new experiences (but also more agreeable and conscientious). Those shifts, combined with the life-changing experiences the 20s bring — college, first love, first jobs, traveling — shape our identities, making us much more comfortable with who we are.

Around age 30, a sense of acceptance begins to settle in. And that acceptance of self makes us much better partners.

Some studies suggest that 35 is the “best age” and that real happiness begins at age 33. People older than 100 years in overwhelming numbers regard their 30s as being the best decade of their lives. Lol.

Still, the 30s have also been found to be a time of existential crises, ticking biological clocks, and heightened job dissatisfaction.

I blame the cerebellum.

But another part of the brain — the cerebellum, in the back of the brain — is not very genetically controlled. Identical twins’ cerebellum are no more alike than non-identical twins. So neuroscientists 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, 30s 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.

And so we think it’s intriguing that we see all these dynamic changes in the cerebellum taking place during the teen years, along with the changes in the behaviors that the cerebellum sub-serves.

What would influence the development of the cerebellum?
Traditionally it was thought that physical activity would most influence the cerebellum, and that’s still one of the leading thoughts. It actually raises thoughts about, as a society, we’re less active than we ever have been in the history of humanity. We’re good with our thumbs and video games and such. But as far as actual physical activity, running, jumping, playing, children are doing less and less of that, and we wonder, long term, whether that may have an effect on the development of the cerebellum.

The recess and play seems to be the first thing that is cut out of school curriculums in tight times. But those actually may be as important, or maybe even more important, than some of the academic subjects that the children are doing. … We think that the “Use it or lose it” principle holds for the cerebellum as well. If the cerebellum is exercised and used, both for physical activity but also for cognitive activities, that it will enhance its development.

… One analogy that computer people use is that [the cerebellum is] like a math co-processor. It’s not essential for any activity. People can get by quite well without large chunks of it. But it makes many activities better. The more complicated the activity, the more we call upon the cerebellum to help us solve the problem. And so almost anything that one can think of as higher thought — mathematics, music, philosophy, decision making, social skills — seems to draw upon the cerebellum. …

The relationship between the findings that we have in the cerebellum and sort of practical advice or the links between behavior are not well worked out yet. That’s going to be one of the great challenges of neuroscience — to go from these neuroscience facts to useful information for parents, for teachers or for society. But it’s just so recently that we’ve been able to capture the cerebellum that no work has yet been done on the forces that will shape the cerebellum or the link between the cerebellum shape or size and function.

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