Paul McCartney suspects that his mother’s death subconsciously inspired the song, “Yesterday.”

On his appearance on The Late Show With Stephen Colbert last night, McCartney discussed whether losing his mother at an early age influenced his work.

“I didn’t think it had affected me musically,” he said. “I just knew it was a tragedy. … And to lose your mum at 14 is, you know, not easy. So it was just very difficult for a few years to try and come to terms with it, but then I discovered music.”

Referring to whether her death directly inspired the lyrics in “Yesterday,” McCartney said, “I certainly didn’t mean it to be. But it could be. Those things can happen.”

Watch the full interview below.