I was thinking of that study of a guy who lived without clocks for several weeks (I think it was underground), and he tended to a 25-hour pattern (IIRC). But of

I was thinking of that study of a guy who lived without clocks for several weeks (I think it was underground), and he tended to a 25-hour pattern (IIRC). But of course (apart from the sample size), he had electric lighting.