Tehching Hsieh performed a year long art performance by locking himself inside a wooden cage furnished only with a wash basin, lights, a pail, and a single bed. He was not allowed to talk, read, write, or listen to radio and TV.
He started this performance clean shaven with a bald head and had someone photograph his progress daily. By the end of the year, he was the long haired hippie you see in this picture. A neat article can be found here.
I took this picture at his exhibition at the Museum of Modern Art in New York.