For his previous documentary, 2009’s “Man on Wire,” James Marsh won an Oscar. That film told the story of Philippe Petit’s death-defying walk across a tightrope stretched between the towers of the World Trade Center. Now comes the director’s new release, “Project Nim,” which revisits the 1970s animal cognition experiment headed by Columbia University professor Herbert Terrace that attempted to teach sign language to a chimpanzee. That chimp, whose name was Nim, happened to be born the same year as the opening of the Trade Center, and as Marsh’s engaging and ultimately poignant film makes clear, the emotional life of one of our fellow primates can be as delicate as a high-wire balancing act.

The director spoke to PLANET about communication, evolution, and other monkey business ahead of “Project Nim’s” release: