People joke about the differences between men and women: Men don't listen. Women can't read maps. Men snore more. Women are less likely to have affairs.
But are men and women really different or are those statements myths?
It turns out that science says men and women are different.
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At the University of Rochester, students were blindfolded and then led through a maze of tunnels that run underneath the campus.
The experimenter stayed behind them and guided them with a tap on the shoulder so they wouldn't run into anyone.
When the women were asked where a college building was, they rarely knew.
Men, however, have a better sense of spatial relations, according to the experiment. Most knew roughly where they were.
In contrast, at York University in Toronto, students were asked to wait in a cluttered room. After two minutes, the experimenter moved them to another room and asked the students to tell him every object in the room that they could remember.
Women typically gave incredibly detailed answers.
The men were more likely to say, "I dunno. There was some stuff there."
Many women went on and on.
Why are there differences like that or more men at the top levels of science?
Is it, as transgendered Stanford University neurobiologist Ben Barres says, all because of sexism? Or is it inborn, caused by the bath of testosterone boys get in the womb?
June Reinisch, a former Kinsey Institute director, studied data on thousands of baby girls and boys, and she concluded there were just inborn differences.
"Girls sat up without support earlier than boys did. Boys crawled independently, away from their caretaker, earlier than girls," Reinisch said.
Still, one could argue that even those differences happen because of some early sexist parenting.
But how do you explain behavior differences in newborns?
"So when they look at babies in the first 72 hours of life, they find that males and females are not identical in the way they behave," Reinisch said. "Males startle more than females. If you give a little puff of air on their abdomen, they startle much bigger and much more likely to startle than females, and females rhythmically mouth. They suck on their tongues. They move their lips and so forth more than males do."
Could this explain the myth that men don't listen?
"The male brain … actually has a harder time processing the female voice versus the male voice, which is a possible explanation to why we don't listen when our wives call us," Dr. Billy Goldberg said on "20/20."
Goldberg and Mark Leyner are co-authors of "Why Do Men Fall Asleep After Sex?"
They said it was true that men listened less because of biology.
"Male babies make less eye contact, for instance, with their mothers than female babies," Leyner said. "So what we're talking about are different ways of relating to people that start at the earliest possible age."
So can men say, "Honey, it's not my fault. It's my brain"?
"I like to use that excuse," Goldberg said.
Despite the book's title, the authors don't have an exact answer for why men fall asleep after sex.
"Science has not figured this one out. It could be that men are more often having orgasms during sex than, than women," Goldberg said.
Another gender myth: Women don't have Adam's apples.
"Well, that's another of these myths that's out there," Goldberg said. "Women do have Adam's apples. They're less prominent than men's."