Fierce rivalries inspire fierce devotion, and Edward vs. Jacob in the "Twilight" saga is the latest example.

Although fans of Stephenie Meyer's popular series of novels know how it ends - whether tormented teenager Bella ends up with vampire Edward or werewolf Jacob - they root as hard as ever for their favorite as the hotly anticipated third film based on the books, "The Twilight Saga: Eclipse," arrives in theaters Wednesday. What does it say about people if they wear a T-shirt emblazoned with "Team Edward" or "Team Jacob"?

Jeremy Clyman, who writes about film in his "Reel Therapy" blog on the Psychology Today website, says just wanting to belong to a group is a fundamental human desire. Which side you choose in "Twilight," though, could stem from personal factors beyond merely thinking Robert Pattinson as Edward is cuter than Taylor Lautner as Jacob - or vice versa.

One of the main things that's exciting about Edward, Clyman said, is that he has a secret: He's a vampire. And that might allow audience members with secrets of their own to identify with him.

"The other appealing thing is the character strength that defines him, his self-control. He's very good at refraining from giving in to his impulses and that could be an appealing trait to see in a person," Clyman said.

Clyman thinks of the more adventurous and muscular Jacob as the underdog in competing for Bella's affection. "She wants to spend time with Edward, and Jacob's stuck in the friend zone."

Kristen Terry of Los Angeles, a self-proclaimed member of Team Jacob who works in photo production, says she can relate to his underdog nature.

"I know I've been in a situation where I was really good friends with a guy and started liking him as more than a friend, but I didn't say anything because I didn't want to ruin the friendship," the 30-year-old Terry said. "Edward was this amazing guy who caught her eye and from the very beginning she was smitten with him."

Jacob also comes in second in fan popularity. In an online poll at the Internet Movie Database (IMDb.com), Edward fans have been outnumbering Jacob fans by about a 2-to-1 ratio.

"Edward personifies that kind of romantic hero from Gothic novels of the 19th century," said Mark Englehart, senior editor of IMDb editorial.

"He's kind of a little like Mr. Rochester in 'Jane Eyre,' the moody, attractive, mysterious man on horseback who comes to sweep the heroine away."

Author Cleolinda Jones, who's written sarcastically funny recaps of the "Twilight" books on her blog, says much of the allure of Edward is that he's a good boy and a bad boy simultaneously.

"He comes from a family with lots of money, lots of stability, lots of security. He goes to school over and over so he's sophisticated, educated. Compared to Jacob he's very calm, very well-read, very clean-cut."

Jacob, meanwhile, is more impulsive, more spontaneous, and comes from a poorer community on the reservation.

"He was probably going to be a mechanic... before he found out he was a werewolf. He's hulky and hairy as opposed to being a clean-cut, elegant figure, so you have the physical contrast."

Marianne Evensen of Norway, a 35-year-old delivery manager who's been attending "Twilight" conventions while visiting the United States, thinks people on Team Edward probably are hopeless romantics, like her.

"Everlasting love is something I strive to live for. I don't want to change friends all the time. I don't want triangles. (Jacob) comes in as an outsider and makes Bella confused."

But she added: "I find both of them hot, though."