London School of Economics and Political Science research as summarized by the Winnipeg Free Press:
People with higher IQs are more apt to be nocturnal night-owls. Those with lower IQs tend to restrict their activities primarily to daytime.
Of course it’s important to note correlation does not imply causation. That said, lots of genius work does happen between 10 PM and 4 AM. There are countless stories of overnight success and innovation. I can’t recall many stories of 9 AM eureka moments unless they were the conclusion of overnight work.