A nice sense of comedic background detail and the winning chemistry of stars Natalie Portman and Ashton Kutcher power No Strings Attached, a comedy in which two young adults test a pact to avoid any deeper feelings while enjoying each other’s company purely for sex. Bantamweight but fun throughout, the movie connects consistently, both on personality and scene-to-scene joke-writing. If there’s a complaint, it’s that Kutcher’s character seems game for a relationship so quickly, and so the movie misses a chance to dig into and as deeply explore the dance of unstated feelings in such an agreement. For the full, original review, from Screen International, click here. (Paramount, R, 107 minutes)