Peek at science behind romantic relationships

Nobody anymore really believes relationships, love and sex are as straightforward as boy meets girl, loves happens, and the couple lives happily ever after.

But now, thanks to the work of a Colorado State University professor and her colleagues around the country, people interested in the topic can get a sense of romance's complexities based on studies rather than clichÉs.

The group has just published a book, "The Science of Relationships: Answers to Your Questions About Dating, Marriage and Family." In addition, the researchers last year launched a website, scienceofrelationships.com, where you can explore a variety of topics such as attraction, cheating and breakups.

"The more work all of us do, the more we realize how much we don't know," said Jennifer Harman, the CSU psychologist.

Fortunately, Harman and her fellow researchers still know quite a bit.

What surprises Harman?

Among many other things, "Women tend to find certain characteristics more appealing during different phases of their (fertility) cycles," she said. "When they are most fertile, they find more masculine traits appealing. But when they are not ovulating, they find more feminine traits appealing, more caregiving traits."

The group has started researching relationships in other countries and cultures, and while they find the differences are profound, at least one thread seems to tie them all together.

Men find a curvaceous hip-to-waist ratio attractive.

"Jennifer Aniston and Anna Nicole Smith, they have different body types, but the ratio is the same," Harman said. "It's a sign of fertility. It's a better indicator of health than body mass index."

At the same time, women find men with nearly 1-to-1 ratios attractive, in terms of hips-to-waist. Women do tend, though, to prefer broad shoulders.

Another basic: In general, opposites don't attract. If you desire a lifelong partner, search for somebody with whom you share interests. Even people with similar body types tend to be better suited for each other, in the long run, than that petite, short woman and the sprawling ex-football player.

The website offers a trove of tidbits.

Under the topic, "Why People Have Sex," the team explored one recent study that identified 237 distinct reasons, ranging from "I wanted to celebrate my birthday or anniversary or special occasion" to "I saw the person naked and could not resist."