<i> Albums are rated on a scale of one star (poor) to five (a classic). : </i>

*** PET SHOP BOYS “Behavior” EMI

“How can you expect to be . . . taken seriously?” the Pet Shoppers ask in one song on what is by far the British duo’s most ambitious album, taking great care to make the tricky rhyme of be and serious-ly sound effortless.

It’s precisely that obsession with putting complex emotions into a simple, seductive pop framework that has made the best of this pair’s witty, sophisticated music so exhilarating: a sort of thinking man’s ABBA. But that same pop sleight-of-hand tends to make the Pet Shop Boys’ singles more enticing than their albums.

The high-tech balance of innocent, Phil Spector-inspired melodic expanse and icy, Roxy Music-influenced sentimental regret is a difficult one--and the team of Neil Tennant and Chris Lowe (who perform a mini-show on Tuesday at the Mayan Club) isn’t always up to the challenge.

A few tracks here--notably “So Hard” and “The End of the World,” two more dips into the sea of heartbreak--reach for the emotional peaks of such earlier Pet Shop gems as “What Have I Done to Deserve This” and “Always on My Mind.”

But these peppy highlights also spoil us, leaving the occasional lapses and the forays into slower tempos flat by comparison. That’s why the Boys’ 12-inch singles are especially effective. They allow you to hear the best songs over and over, in various mixes, without the lapses.