Maddie, age 14, is head over heels for Justin Bieber. The 17-year-old pop sensation is ranked third on Forbes’ list of the 100 most powerful celebrities, and is as famous for his cotton candy voice as his awe-shucks smile and floppy hairstyles. Maddie finds him “extremely good-looking” and wants to tell him that they should hang out “because, you know, that would be awesome.” Millions of girls agree.So does her mom.Marlys, age 48, borrows Maddie’s iPod to listen to Justin Bieber on the treadmill. She loves “Overboard,” admires Justin’s devotion to his family and enjoys dancing to his music.She is not alone. Readers: Meet the Bieber Boomers.According to an informal survey from Popeater, a widely read pop culture site, more than three-quarters of Bieber fans fell into two categories: under 17 and over 40. A full 21 percent were over 40.

Grace, age 54, first listened to Justin Bieber when she purchased his CD for her 8-year-old granddaughter. “I’m hooked,” she says. She describes him as “a young Donny Osmond—the cutest little guy,” and says that his music makes her feel loved.

It’s no coincidence that females two to three generations apart are falling for the same teen music sensation. Like most cases of puppy love, hormones are to blame.

READ MORE: Love is a Beauty Treatment

The Estrogen Effect:

Justin Bieber’s boyish looks and high-pitched vocals have charmed millions of women at opposite ends of the age spectrum. What do they have in common? Low estrogen.

“Before puberty, women prefer men with more feminine faces and higher voices,” says Tony Little, Ph.D., Royal Society Research Fellow in Psychology at the University of Sterling. The same holds true after menopause. “Post-menopausal women almost revert back to a pre-puberty level of preference for more feminine men.”

In a 2010 study demonstrating this effect, Little and colleagues showed two images of a male face, altered to look masculinized or feminized, to women of different ages. Feminine faces appealed to post-menopausal women and girls in the early stages of puberty, while women in their most fertile years preferred more masculine men.

READ MORE: Menopause and Skin

Little believes that estrogen may fuel the changes. “Estrogen kicks in quite strongly at puberty,” he says. “It encourages women to want to mate with genetically high-quality [read: masculine] men.” As estrogen dwindles post-menopause, so does the affinity for hunky, masculine men. Hence: Biebermania.

What’s Love Got To Do With It?

Linda, age 62, smiles whenever she hears Justin Bieber’s voice. “He brings me back to the 60s, when the Beatles and the other British bands had similar hair and clean, cute faces.” Grace agrees that he makes her feel “young at heart.” He’s a throwback to their teenybopper days.

But are older women really attracted to him, as “Saturday Night Live” would have you believe? (In a popular skit, Tina Fey falls in love with guest star Justin Bieber and exclaims, “I don’t know if I want to marry him or put him in a stroller and push him around the mall!”).

To Aleah, age 14, Justin Bieber is “everything.” She plans to marry him one day and knows that his favorite number is six. She puts Chapstick on his posters so his lips won’t get dry and kisses him goodnight before bed. She’s the quintessential Belieber, totally devoted to becoming Mrs. Bieber.The Bieber Boomers have a different mission: “If I met Justin Bieber,” says Marlys, “I would say, ‘Hi Justin, this is my daughter Madeline!’”

All in the Family:

Ulterior motives aside, Bieber inspires female bonding across generations.“Maddie doesn’t mind me listening to his music,” Marlys says. “It allows her to share her love of Justin’s music with someone in the family.” Maddie even thinks it’s “really cool” that her mom listens to him and says, “Not enough moms do, in my opinion!”

Grace has a similar experience with her granddaughter. “We listen, sing and dance to his tunes,” she says. “It gives us quality time together sharing our feelings. We’ve bonded.”

READ MORE: Your Mind on Music

It’s probably hard to live with a tween girl without getting a little hooked. Bieber’s music is catchy and easily gets stuck in your head (as this writer’s neighbors can attest). “Justin can be contagious!” says Marlys.He certainly can, and women have caught the fever in droves. Those of us between ages 17 and 40 have estrogen staving it off, but give it time. According to science, you’ll catch Bieber Fever too.

DISCUSS: What helps you bond with women of different generations in your family?