What is needed for both boys and girls are better objective tests, like blood flow measurement to the putamen, to distinguish between biological abnormalities and natural boisterousness. The new brain-scanning technique used for the Ritalin studies is also employed for studies of how childhood abuse can produce lifetime changes in the brain and, hence, behavior. At ages 5 to 7 years, an abundance of new connections among nerve cells are being made in the brain. This activity peaks at puberty, then the luxuriance of connections undergoes a natural pruning. He follows this natural cycle by examining the brains of rats, which mimic the changes in humans on a much shorter time scale.
Girls undergo markedly less overproduction and pruning than boys.
The reason probably involves early exposure to testosterone and other male hormones that determine the course of brain development. As children reach adolescence they become more vulnerable to schizophrenia, a serious disturbance in thinking, emotions, and behavior. The malleability of young brains leads to other problems when their owners are victims of physical and sexual abuse and witnesses to violence at home and other traumas. Brain scans show fewer nerve cell connections between the left and right halves of the brain. Fewer connections may result in a reduced ability to use thought and logic to control emotions.