Excerpt from Raising Cain by Dan Kindlon, Michael Thompson Ph.D., plus links to reviews, author biography & more

The results? The girls were less upset by the crying. They made greater efforts to calm the baby and less often moved to turn the speaker off. Boys whose heart rate pattern showed that they were quite stressed by the crying also were quick to "turn off" the crying with a flip of the speaker switch. These distressed boys were also more likely to act aggressively toward the baby--telling it to "shut up," for instance. Boys whose heart rate showed a lower stress level were more likely to comfort the infant. The researchers theorized that children--in this case, boys--who are more easily stressed by emotional responses may prefer to avoid them. In other words, boys who have trouble managing their own emotions may routinely tune out the cues of other people's upset.

Boy Biology: No Simple Answers

In the wake of a 1998 schoolyard killing in Jonesboro, Arkansas, a journalist asked us about "the nature-nurture question," whether the boys' violence was genetic or the result of how they'd been raised. Her implicit assumption was that boys are prone to violence because of their biology. Certainly, male hormones were present at the scene: every boy has them. But we think the intensity of discussion about boy biology obscures the more meaningful and urgent issue of how we raise boys in this culture.

We answered the reporter's question with an apocryphal anecdote about a famous psychology professor who said that he had studied the nature-nurture question with great care, reading all the literature, and had finally come to a conclusion: nature wins--by a score of 53 percent to 47 percent. The reporter laughed, seeing both the humor and the truth contained in the statement--that clearly everything we do is influenced heavily by both. Then we asked her why it is that there is always such an exclusive, determined hunt for a biological culprit. She paused and said, "Well, people are looking for simple answers."

But human behavior defies simple explanation, whether we're talking aggression or tenderness. What is clear is that every behavior is influenced by multiple forces, from biology to community. The "nature or nurture" debate sidesteps the genuine complexity of these issues. Rather than making it a contest between the two, current thinking in the neurosciences highlights the inextricable link between biology and experience, and it is now widely recognized that environmental factors can affect the structure of our brain.4 An extreme example is a trauma victim whose body releases stress hormones over a long period, which cause physical damage to parts of the brain, which in turn will affect how he behaves. On the other hand, brain functioning can be enhanced by various learning experiences, such as being in an environment rich with exposure to letter shapes and sounds. These experiences will shape his brain--new neurons may actually be created--and a child will end up with a greater ability to read than he "was born with." The bottom line: heredity isn't destiny.

There are, however, two clear biological differences between boys and girls that have been shown to have an impact on development and behavior. The first, which we discuss more fully in chapter 2, is that girls' verbal abilities, on average, mature faster than boys': they talk earlier and more fluently. Boys tend to catch up later, but in the early grades especially, feminine superiority in this area is readily apparent to parents, teachers, and researchers. The second difference is that boys tend to be more physically active than girls, moving faster and staying in motion longer. As we shall see, this propensity for activity and the consequences of it shape a boy's every experience and the way others experience him.

Other than these, there are not many developmental differences that are clearly biological in origin. Even the celebrated superiority of boys in math skills cannot be reduced to boy biology. Many studies of gender difference in math performance show that overall the girls tend to do slightly better.

Excerpted from Raising Cain by Dan Kindlon and Michael Thompson. Copyright© 1999 by Dan Kindlon and Michael Thompson. Excerpted by permission of Ballantine, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.