Education in United States

More than the book GEB, I find Douglas Hofstadter's description of his education more interesting that the book itself ...

[I]n late 1967 ... I dropped out of math grad school in Berkley and took up a new identity as physics grad student at the University of Oregon in Eugene. ... I was very discouraged with the way my physics studies and my life in general were going, so in July I packed my all my belongings into a dozen or so cardboard boxes and set out on an eastward trek across the vast American continent. ... From Boulder I headed further east, bouncing from one university town to another, and eventually, almost as if it had been beckoning me the whole time, New York City loomed as my ultimate goal. Indeed I wound up spending several months in Manhattan, taking graduate courses at City college ... but as 1973 rolled around, I faced the fact that despite loving New York in many ways, I was even more agitated than I had been in Eugene, and I decided it would be wiser to return to Oregon and to finish graduate school there. ... In 1974, I switched Ph.D. advisors for the fourth and final time ...

Wow!
Can you do that? I mean, switching subjects, schools & university, and professors at will?