I find the latest scientific hubub a tiny bit irking. If you haven't heard, the media is pushing a new study saying that the risk-avoidance portion of the brain doesn't finish developing until around age 25. I'm having a hell of a time finding even an abstract for the study -- why do pop science writers insist on avoiding proper citation? But I've still got two more weeks of youthful recklessness to enjoy, so allow me to charge ahead without having seen the study and explain why I think this is junk.

First, what does this "not done forming" thing really mean? Odds are pretty good that they mean the frontal lobe hasn't finished myelinating. Myelin is a fatty sheath that coats your brain's axons -- this allows for much faster and more efficient conduction of nerve impulses. It's a good deal -- nasty things happen when you lose your myelin, MS being the classic example. Contrary to the "aha!" flavor being attached to this study, my intro to neuroscience textbook was pretty clear about the fact that myelination doesn't conclude until at least your early twenties.

But more to the point, it's not perfectly obvious that incomplete myelination always translates to poorer performance. If memory serves, myelination inhibits neural plasticity -- this is the preferred explanation for why young kids are better at picking up languages. And while the frontal lobe is considered to be essential for deliberate planning, it's tough to translate a slight morphological difference into a causal factor. If you remember high school psychology, you recall how Phineas Gage is the textbook lesion study used to answer "what does the frontal lobe do?" For those who don't remember: Gage got most of his frontal lobe (and connecting fibers) shot out by a railroad spike. Cool, I know. But his personality changed immediately from that of a thoughtful, deliberate person to that of a profane, lazy jerk with wild mood swings.

So yeah, it's tempting to lump all these symptoms together and say "youth is a disease of the frontal lobe!" But do we really think that part of the brain goes offline at age 12? Or could the mood swings be the product of something more related to the Hair that suddenly shows up Down There?

Well, who knows; maybe the sudden influx of hormones somehow screws up frontal lobe performance. Maybe it does something else entirely. The point is just that establishing causation in neuroscience is tough to do unless you have the luxury of lesioning your subjects. Instead the best we can usually do is come up with somewhat suggestive anatomical studies such as this one.

If this study correlated myelination with whatever Analytic Risk Taking Protocol is officially used to measure these things, it might be a little more definitive -- but as far as I can tell from the articles I can find about it, this is a purely biological study.

But that fact won't stop the science press from running with it, like on the last page of this Post story. Apparently teens playing a driving videogame take more risks than twentysomethings when they're in front of their friends. By jamming this factoid together with the other study, we're supposed to conclude that the difference comes from frontal lobe development. Personally, I suspect it's got more to do with us having had a few extra years to get bored with the Grand Theft Auto series of videogames.

But again: who knows?! The point is just this: everyone wants to quantify What's Wrong with those Damn Kids, but a correlation this weak (a several year gap between biological process completing and the perceived peak of irresponsibility) isn't exactly conclusive.