Two years after a Stanford professor drew 160,000 students from around the globe to a free online course on artificial intelligence, starting what was widely viewed as a revolution in higher education, early results for such large-scale courses are disappointing, forcing a rethinking of how college instruction can best use the Internet.

A study of a million users of massive open online courses, known as MOOCs, released this month by the University of Pennsylvania Graduate School of Education found that, on average, only about half of those who registered for a course ever viewed a lecture, and only about 4 percent completed the courses.

Much of the hope — and hype — surrounding MOOCs has focused on the promise of courses for students in poor countries with little access to higher education. But a separate survey from the University of Pennsylvania released last month found that about 80 percent of those taking the university’s MOOCs had already earned a degree of some kind.

And perhaps the most publicized MOOC experiment, at San Jose State University, has turned into a flop. It was a partnership announced with great fanfare at a January news conference featuring Gov. Jerry Brown of California, a strong backer of online education. San Jose State and Udacity, a Silicon Valley company co-founded by a Stanford artificial-intelligence professor, Sebastian Thrun, would work together to offer three low-cost online introductory courses for college credit.