Christopher Nolan is known for writing and directing notoriously complicated yet genius films like Inception and Memento. And while many of his movies use cutting-edge technology to bend our minds, on set, he enforces a strict no-phone policy, Esquire reports.

Nolan spoke with Adam Grant, PhD, a professor of organizational psychology at University of Pennsylvania’s Wharton School, for Esquire’s August issue, which resulted in some fascinating questions and answers. On not allowing phones on set, Nolan explained that it boiled down to people on his sets thinking they were better at multitasking than they really were.

“There’s a mass belief that if you’re texting, you’re somehow not interrupting the conversation…it’s an illusion of multitasking,” Nolan told Grant. He said that when he started making films, having phones around was both rare and taboo: “it would’ve been seen as unprofessional to pull out a phone.”

Nolan said people initially had a hard time letting go of their beloved smartphones, but he feels his crew can concentrate better without them and said some crew members have even thanked him for enforcing the rule. (And really, who would chose their phone over working on a Christopher Nolan set?)

The no-phone rule stems in part from a desire to keep the “alternate bubble of reality” Nolan tries to build on set intact. “If you have people in a creative environment where they have to concentrate on what they’re doing, you can’t have them wandering off in their minds”—and phones are certainly a portal for endless mind wandering.

This is a good reminder that even a “trailblazing director, screenwriter, and producer—one of the rare auteurs of our time,” as Grant described Nolan, needs to unplug in order to focus on the task at hand.

Read the full interview here