Finally researchers have come up with a reason other than pure laziness for why teenagers can't shower and brush their teeth or unload the dishwasher and wipe down the counter.

Blame it on "cognitive limitations." Their brains can't multitask as well as those of the taskmasters.

Trust, however, that they'll grow out of it.

The part of the brain responsible for multitasking continues to develop until late adolescence, with cells making connections even after some children are old enough to drive, according to a new study in the May/June issue of the journal Child Development.

The frontal cortex, which starts just behind the eyes and goes back almost to the ears, figures out (or doesn't) what to do when a person is asked to juggle multiple pieces of information. Imagine, then, how "make your bed and bring the laundry down" might befuddle a 13-year-old.

In one of the study's tests, subjects between ages 9 and 20 were given multiple pieces of information, then asked to re-order the information to formulate an accurate response to a question. In another of several tests, they were asked to find hidden items using a high degree of strategic thinking.

The ability to remember multiple bits of information developed through age 13 to 15, the study found. But strategic self-organized thinking, the type that demands a high level of multi-tasking skill, continues to develop until ages 16 to 17.

The notion is not entirely new. Brain imaging has suggested as much.

"Our findings lend behavioral support to that work and 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," said lead researcher Monica Luciana, an associate professor of psychology at the University of Minnesota.

Unfortunately the study did not reveal any solution to parents at their wits' end over the problem. But Luciana did offer this advice:

"We need to keep their cognitive limitations in mind, especially when adolescents are confronted with demanding situations in the classroom, at home, or in social gatherings."

Related Stories