<p>All that shows is that the tests only measure cognitive skills that are developed through age 12 .... which any one who had raised kids or taught various ages would figure out for themselves. At age 12 the kids hit what Piaget called the level of formal operations, which means they can think abstractly and logically and probably do well with whatever form of testing is used to assess basic cognitive skill levels. The brain growth that continues to take place through adolescence and into the 20's has more to do with the prefrontal cortex, which is involved with executive function, impulse control, and basically exercising good judgment and making appropriate decisions. </p>
<p>Which is why we don't give driver's licensed to 12 year olds, even though they are perfectly capable of learning to steer the thing and use the brakes & accelerator (assuming they are tall enough to see over the steering wheel). But managing all the rest is tough even for 15 year olds with learner's permits. It's one thing to pass a skills test which requires a person to do simple tasks, one at a time.... it is quite another thing to navigate the constant multitasking and decision-making required for real life.</p>