No More Kid Stuff for Taylor Swift Ethan Miller/Getty Images; Christopher Polk/Getty Images, for Clear Channel Taylor Swift in 2007, left, and last month, right. AWE and amazement have been Taylor Swift's grammar for years now. Whether singing about love or heartbreak - there has been no third subject - Ms. Swift has excelled at capturing the fresh sting, as if arriving at a feeling for the first time. Brian Doben Taylor Swift has always been a pop star in a country context more than a country star. But Ms. Swift is 22 now, and certainly she has seen some things. For most of "Red," her fourth album, that's not necessarily clear. Her growth is largely musical, not experiential. There is a moment, though, on "We Are Never Ever Getting Back Together" - the album's lead single and, as it happens, her first No. 1 pop hit - where the cracks begin to show. At the bridge the song gives way to a conversation between Ms. Swift and friends in which she's recalling how she shut down a persistent ex who wouldn't stop calling. "This is exhausting," she tells him, emphasizing the middle syllable of the last word, like a car that's just run out of gas. There is something different in Ms. Swift's voice here: it's serious and deep, and also shrewd. She has been through this before. She sounds like an adult. It's about time. Though often great, it is her least steady album, with some of her most sheer songwriting. She is showing maturity less as an adult - though there is some of that - than as a strategist. The most blatant stroke of pop engineering here is Ms. Swift's work with the pop-production technicians Max Martin and Shellback, which would be the clear choice for any singer looking for a loud pop splash. But for Ms. Swift, who has generally kept her circle of collaborators tight and done just fine with that, it was almost as unlikely as her working with Vybz Kartel or Gucci Mane. Each of the three songs written with Mr. Martin and Shellback feel like inside jokes about the squeaky-clean pop of eras past. "We Are Never Ever Getting Back Together" has a Disney-esque literalness, and "22" feels like cheeky "80s pop. "I Knew You Were Trouble," one of the year's great pop songs, begins like a sock-hop anthem, with jaunty guitars. A dubstep wobble arrives about halfway through like a wrecking ball, changing the course not just of the song but also of Ms. Swift's career. She also worked with the pop producer Jeff Bhasker on a pair of songs, "Holy Ground" and "The Lucky One," that don't take her out of her genre comfort zone but do amp up the intensity.