Researchers say brain development continues through adolescence.
That teen talking on the cell phone, sipping a soda and ostensibly doing homework, all while the television blares, probably is not, in fact, particularly good at multitasking.
University of Minnesota researchers, in a study, used mental challenges to confirm that the part of the brain responsible for the ability to multitask continues to develop until late adolescence.
"When we use tasks that would be challenging even for a healthy adult, it becomes apparent that teenagers are still developing the cognitive skills necessary to efficiently manage multiple pieces of information simultaneously," said Monica Luciana, an associate professor of psychology and lead researcher for the study, published recently in the journal Child Development.
"These findings have important implications for parents and teachers who might expect too much in the way of strategic or self-organized thinking, especially from older teenagers," Luciana said.
Up until a few years ago, most brain experts thought the human command center stopped growing at around 18 months, and that neurons were pretty much set for life by age 3.
Now they know from brain-imaging studies that the gray matter has a final growth spurt around the ages of 11 to 13 in the frontal lobes of the brain. Those regions guide intellect, planning and the ability to juggle multiple pieces of information, think flexibly and control behavior when confronted with challenges.
But it seems to take most of the teen years for adolescents to link these new cells to the rest of their brains and solidify the millions of connections that allow them to think and behave like adults.
Luciana and her colleagues sought to better quantify how the region -- just behind the eyes to just in front of the ears -- matures and improves through adolescence.
They had 9- to 20-year-olds complete behavioral tests designed to measure functioning of the frontal cortex.
One task involved recognizing previously presented faces, while a second involved looking at the location of a dot on a computer screen, and then, after a delay, indicating where the dot had been. These tests assessed "working memory," or the ability to use recognition or recall to guide future actions.
A third test required that the youths remember multiple pieces of information in the correct sequence and sometimes re-order the information in their memory before responding to a question. A final test called on the youths to search for hidden items that required a high level of multitasking and strategic thinking.
The researchers found that the ability to use recall-guided action to remember single pieces of spatial information developed until about age 12, while the ability to remember multiple units of information developed until ages 13 to 15. But the development of strategic, self-organized thinking, which demands a high level of multitasking skill, continues until 16 or 17 in most teens.
"Our findings indicate that the frontal lobe is continuing to develop until late adolescence in a manner that depends upon the complexity of the task that is being demanded," Luciana said.
The skills improve over time as connections between brain cells in the frontal lobes become more refined, enabling more information to be simultaneously managed, she said.