Spike Jonze loved working with Scarlett Johansson on Her, and has praised her performance calling her 'smart as hell'.

The director told People magazine, "Scarlett is not afraid of revealing her pain and emotions. She's attractive, but also smart as hell. She's in some renaissance age, where she is pushing herself to new places. She wants to go deeper and is taking risks."

Johansson plays the role of a computer that falls in love with a human in Her, which also stars Joaquin Phoenix. It's scheduled for release on February 14.