When it comes to humor, women may have lower expectations.
Scientists are finding a myriad of differences between the way men's and women's brains function. In one of the most recent studies, researchers watched brain activity as men and women read cartoons and found that women's brains show higher reward activation when they find something funny.
This suggested to the researchers that while the men and women found punch lines equally funny -- or unfunny -- men's brains expected to be amused and women's didn't.
"Women appeared to have less expectation of a reward, which in this case was the punch line of the cartoon," said Allan Reiss at Stanford University's Center for Interdisciplinary Brain Sciences Research. "So when they got to the joke's punch line, they were more pleased about it."
The researchers used functional MRIs -- scanning devices that measure blood flow and activity in the brains of conscious subjects -- to watch brain activity in the 10 men and 10 women as they read 48 cartoons. The technology revealed that women activated parts of the brain involved in language processing and memory more than men. The reward center of the brain also 'lit up' more in women's brains once they were amused.
Though it was a very small study, it is the latest in a string of research suggesting differences in the way men's and women's brains function. Previous work has found differences in the way we understand speech, the way we encode memories and how we develop the ability to speak.
Some scientists say we're bound to continue finding differences between the genders since the different processes required to make a man or woman during early development surely affect a number of "switches" in the brain.
"When people started looking at sex differences in the brain, some were scared by it," said Geert J. de Vries, a brain researcher at the University of Massachussets at Amherst. "But I don't think it's cause for any concern. It's simple -- the male brain is designed to function best in a male body and the female brain is designed to function well in a female body."
De Vries explains the brain is so complex that many systems have more than one function. "They can juggle and rub their bellies at the same time," he explains. That means when a gene signals the body to create testes rather than ovaries, the signal likely influences more than the making of the male or female organs.
"A hormone is secreted to make that change, but it has to be activated in every cell of the body. That spells out a huge difference that is acted out in every cell," he said. "In the brain, these differences can affect behavior and process."
If this latest research holds up, it appears even the process of finding something funny or unfunny could be influenced by sex difference.
"At first glance it looked like there was similar activation between the men and women," said Eiman Azim, a co-author of the new study appearing in the Proceedings of the National Academy of Sciences and currently a doctoral candidate in neuroscience at Harvard University. "But then we saw women had higher activation in certain regions than men. It seems like men and women approach jokes with different brain activity and expectation even though the end result is the same."
Then again, there is always room for error -- especially in a study with a scope as small as this one.
"Humans are so variable," said de Vries. "With such a small sample size, it could just be that the men in the study had heavy breakfasts and the women didn't."