Sophia is the new No. 1 name for girls, moving the most popular girls' name for the past two years -- Isabella -- to second-best. Mason was No. 2 on the boys' list. The federal agency notes that although Mason has been a relatively popular name since the 1990s, it had never reached the top 25 names until 2010. That's when it hit No. 12, suggesting the rise may be due to reality TV star Kourtney Kardashian's son, Mason.
Recent baby name trends reflect influences of celebrities, pop culture and society, notes Pamela Redmond Satran, who has followed baby names for decades. In 1988, she co-authored the first of 10 baby-name books. She also co-founded the baby-name website Nameberry.com.
"Classic, gender-specific names" that suggest "a more serious image of women," have emerged, she says, such as the new list's first-place Sophia and second-place Isabella as well as Olivia, which ranks sixth in the new list.
Satran says celebrities take their baby names to new extremes. Blue Ivy, the name picked by Beyonc and Jay-Z for their first child, refers to the parents' favorite color and the significance of the number IV - (4) - in their lives.
But sociologist Patricia Leavy, an expert on pop culture at Stonehill College in Easton, Mass., says when regular people emulate the names celebrities choose, they risk some pushback.
"The average person doesn't live in the world that a celebrity does," she says. "If you pick an unusual name, your child will get attention for that, which may or may not be positive."
Leavy says the focus on a special name is particularly important among today's parents.
"They want their child to stand out and they're afraid if they have four children in the classroom with the same name their child won't stand out," she says.
Lisa Hynes, 27, a stay-at-home mom in Phoenix, says she and her husband, Evan Hynes, 26, sought uncommon names for their two children, Zayden Patrick, 2, and Azlynn Mae, born March 29.
"We didn't want either of our kids to be like the fifth Ashley in the class," she says. "I have four friends named Jessica."
But new research on baby names to be published in the journal Psychological Science finds that even though parents strive to be unique in their choices, they often select names that sound like the popular ones. Jonah Berger, an assistant professor of marketing at the Wharton School of Business at the University of Pennsylvania in Philadelphia, says the "mechanism here is similarity."
"People like things they've seen more or they've heard more. The more 'Katherines' you hear not only affects how much you like 'Karen' but other names that begin with the K sound," he says, meaning that parents "unconsciously end up picking a name that's very similar."
"Everyone is trying not to end up with six Jacks in same classroom, but they end up with six kids with names that start with J," he says.
Names on the Social Security list are compiled from names parents give when they apply for a child's Social Security number. The agency, which has tracked baby names since 1880, posts the list at its website, www.socialsecurity.gov.
This year's winners for biggest jump in popularity in the Top 500 are Brantley and Briella, notes the federal agency, suggesting that the fastest riser among girls may come from Briella Calafiore, the reality TV hairdresser from the Style network's Jerseylicious and Glam Fairy. For the boys, the website suggests Brantley could be for quarterback John Brantley of the University of Florida or from Brantley Gilbert, the country singer.
Other top boys and girls names for 2011 include William and Emma rated at third, followed by Jayden and Olivia and then Noah and Ava at No. 5.
By Sharon Jayson, USA TODAY
The top 20 baby names of 2011:
Source: Social Security Administration.