One Direction's one direction appears to be up. The 'What Makes You Beautiful' singers performed an acoustic set for some lucky Chicago fans, in addition to announcing added dates to their U.K. arena tour.

The 'X Factor U.K.' alumni started their show with a Q+A, during which it was revealed that Zayn Malik does the best American accent, but Niall Horan is rather skilled at Valley Girl imitations. (Seriously, how lovable are these guys?) Their dream duets include Katy Perry, Adele and Jessie J.

In their acoustic performance of 'What Makes You Beautiful,' you almost can't hear them in the beginning -- because all of their fans are singing over them! Soon the crowd eases up, and you can hear their soaring harmonies loudly and clearly. It becomes immediately obvious why they're so successful in the States already: they sound fantastic.

‘What Makes You Beautiful,’ debuted at No. 28 on the U.S. Hot 100. The track sold 132,000 downloads, placing at No. 12 on the Digital Songs chart. It’s the highest chart debut from a U.K. act since 1998 -- which is even more impressive when you learn that the song hadn’t even been released to radio yet!

Meanwhile, Stereoboard reports that at home across the pond, the band's arena tour has been so successful that they've had to add dates on to accommodate (can capitalize on) the high demand. Their U.S. tour with Big Time Rush kicked off yesterday. We expect to be hearing a lot more from One Direction, and we couldn't be happier about it!

Watch One Direction Sing 'What Makes You Beautiful' in Their First U.S. Performance