CHAMPAIGN, lll. - When it comes to violent nonfiction, men are from Mars, the planet of war, but women are from Earth, the planet of serial killings and random murders.

A new study found that, when given a choice of violent reading material, women overwhelmingly opted to read true stories about the death and dismemberment of victims much like themselves. Men, however, were more likely to choose nonfiction books about war or gang violence than those in the "true crime" genre.

The study appears in Social Psychological and Personality Science.

"We found that women were more likely than men to choose the true crime book versus the war or the gang violence book and also that they expected to enjoy it more," said Amanda Vicary, a graduate student who conducted the study with University of Illinois psychology professor R. Chris Fraley.

The research began with an analysis of reviews posted on the Web site Amazon.com by readers of books in the true crime and war genres. Coding usernames for gender, the researchers found that women wrote 70 percent of the reviews of books about true crime, while men wrote 82 percent of the reviews of books on war. The gender of the author appeared to play no role in women's preference for true crime books.

A second study gave participants summaries of two books and asked them to choose the book they would rather read. One summary was a "true account" of the murder of two women in Hawaii. It was paired with either a true story of two female soldiers who died in a Gulf War army unit, or a true account of two female members of a Los Angeles gang who were killed.

Women overwhelmingly chose the true crime books over the books about war or gang violence, even when the main characters of all of the books were female. The men chose the true crime books about half the time when the other book was a true war story and both books had female main characters. The men were somewhat more likely to select the true crime book with female characters over the gang book with female characters, but by a much smaller margin (57 percent) than the women (73 percent).

"Research that has been done in the past about gender and aggression has established pretty clearly that men are more likely to commit violent crimes and they're more likely to be the victims of violent crimes," Fraley said. "So these basic observations are extremely surprising to us. Why are women more drawn to the true crime genre than men are?"

The researchers suspected that women like true crime stories in part because such stories provide information that the readers feel could help them avoid or escape from a potential attacker. Previous studies have shown that women are much more likely than men to fear becoming crime victims, and there may be an evolutionary benefit to learning from others' negative experiences, Fraley said. Perhaps the fear of an attack and the desire to avoid becoming a victim drives many women to read true crime stories, he said.

To get at this question, the researchers conducted three more studies in which the summaries of the books included details that might help explain the choices women made. They found that women were much more likely than men to choose a book if it included a "clever trick" the would-be victim used to escape from an attacker, or a psychological profile of the attacker. And women, but not men, were much more interested in books with female victims.

"The male participants didn't care either way," Vicary said. "They were pretty evenly split, whereas the women wanted to read about the women getting killed."

The findings spur many more questions than they answer, the researchers said.

"Why are women differentially fascinated by understanding true crime?" Fraley said. "This study takes us one step toward trying to understand how the mind works, what it is that people prefer and why."