Researchers say teenagers are sulky and inconsiderate because their brains are changing rapidly.

As one expert put it, "Teenagers' brains are still works in progress."

A new study says tests show humans do not fully develop the ability to empathize with others or consider others' emotions and thoughts until adulthood.

Sarah-Jayne Blakemore of the Institute of Cognitive Neuroscience, University College London, who led the work, said her research "suggests ít's not just hormones that cause teenagers to be their typical selves, but it could be the way their brains are developing as well."

Copyright 2006 by United Press International