See One, Want One: The Roots of 'Baby Fever'

If the sight of a rack of baby shoes at the store gets you longing for an infant of your own, rest easy: You probably have baby fever, and psychologists have just confirmed that you're not alone.

Long immortalized in television and movies, "baby fever" is indeed real, a new study confirms. This visceral, emotional desire for a child is more common in young women than men, the research found, although as they age, men are increasingly at risk for what's also known in pop culture as "baby lust."

"How frequently women have the desire to have a child goes down with age, and down as they actually have children," study researcher Gary Brase, a psychologist at Kansas State University, told LiveScience. "For men, it tends to go up. … It's like men and women are converging over time." [Read: Top 12 Doting Dads in History]

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The baby decision

Brase researches judgment and decision-making, and was inspired to turn his attention to reproductive decisions after he and his wife experienced their own bouts of baby fever. Brase was surprised to find that no one had ever researched the phenomenon given how large a life decision it is to have a baby.

"If you talk to a biologist, they say, 'You want to have children because passing on your genes is the reason why you're here,' but if you talk to an economist, they'd crunch the numbers and say, 'This is a horrible investment idea,'" Brase said.  "If you try to do a rational cost-benefit analysis, having a child doesn't make sense. But if you look at it biologically, it's the only thing that makes sense. And then there's actual people that somehow figure it out between those two." [Read: America's Most Hated Baby Names]

To uncover the role that emotion and desire play in this decision, Brase and his colleagues completed three studies. The first, with 80 undergraduate students, used questionnaires to establish that people do, in fact, experience baby fever. The students also answered questions about factors that made them more or less likely to want a baby ("lack of money," for example, tends to mitigate baby fever).

To distinguish "baby fever" from a more clear-headed desire to have kids, the researchers asked volunteers if they ever feel "a bodily desire for the feel, sight and smell of an infant next to you." Women's average rating of how frequently they experience baby fever was 4.22 on a scale of 1 to 9, compared with 2.69 for men.

A follow-up study of 252 more students confirmed that women more frequently desired a baby than men. The researchers had suspected that socialization might play a role, theorizing that women who more strongly believed in traditional gender roles might also desire one of those roles — motherhood — for themselves. That turned out not to be the case, Brase found.

"Gender role norms didn't do much as far as explaining people's desire to have a baby," Brase said.

Weighing the pros and cons

Using data from the first two studies to build questionnaires, the researchers then recruited volunteers via the Internet, gathering an older and more diverse group than the earlier student populations. Again, the results showed that women tend to  experience baby fever more than men, while men report more frequent desire for sex, "which is interesting," Brase said, "because they're related activities."

But comparing volunteers of different ages, the researchers found that women's baby fever usually decreases with age and motherhood, while men's baby fever increases as time goes by. Fortunately for humankind's continued existence, the two genders converge briefly in their level of baby fever in their 30s. By their 40s, men report more frequent baby fever than women of the same age.

Brase isn't yet sure why this switch takes place. He did find, unsurprisingly, that pleasant experiences associated with babies, such as seeing a happy infant or adorable baby clothes, increased baby fever, while experiences with dirty diapers and other unpleasant day-to-day realities threw cold water on the desire to have a kid. People also consider trade-offs, such as loss of money or stalled professional goals, Brase said. And the world is not divided into baby-lovers and baby-haters, the results showed. Many people have strong positive and strong negative associations with babies at the same time.

"People see a cute baby, and then they say, 'Oh, I want a baby,' but then they're also thinking about all the time and money and lost sleep and so on," he said. "Those can work against each other and yet still be in the same person."

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.