Boy or girl? Even before a person is born, that's the first thing everyone wants to know—underscoring just how much value human societies of all types place on gender.

The great divide between male and female has inspired poets, intrigued biologists and spawned an entire industry of self-help books. It has also given rise to a few misconceptions along the way, such as the notion that smaller brains make the so-called fairer sex inherently less intelligent—or at least bad at math.

In this special edition of Scientific American Mind, we take a closer look at gender and the brain. In these pages, you will learn about a variety of male-female differences—and also some surprising similarities.

For instance, studies of baby boys and girls—such as the ones described in “Big Answers from Little People,” by David Dobbs, on page 20—find few differences in their cognitive skills. But there is no denying that boys love trucks, whereas girls prefer dolls—and the same is true of male and female monkeys. Some differences between boys and girls are evident even on the first day of a baby's life.

Most of these discrepancies start out small but get amplified by our gender-obsessed culture. As neuroscientist Lise Eliot explains in “The Truth about Boys and Girls,” on page 12, tea parties and wrestling matches leave their stamp on growing brains. The gap that separates boys and girls would be less noticeable if parents encouraged activities such as reading for boys and video games for girls.

By the time they reach adulthood, males and females not only have nonidentical brain architectures but also divergent ways of speaking, parenting and responding to both tragedy and comedy. “The Humor Gap,” by Christie Nicholson, starting on page 66, and “Different Shades of Blue,” by Erica Westly, beginning on page 34, explore these divides. She wants someone who can make her laugh. He wants someone who will laugh at his jokes. And when she's depressed, she gets sad. He gets mad.

But men and women aren't from different planets. Few sex disparities are as hardwired as popular accounts make them out to be. A better understanding of the real—and imagined—differences between his brain and her brain can help us overcome cultural biases, improve communication and strengthen relationships.