A Harvard University professor who made attendance at lectures optional, with students being allowed to watch video recordings instead, has reversed the policy after just 12 months.

Last year David Malan, Harvard’s Gordon McKay professor of the practice of computer science, told the 800-plus students on an introductory programming course that they would be required to attend only the first and last lectures of the module in person.

But the course material for CS50, which is Harvard’s largest course, now features the statement: “Unlike last year, students are encouraged to attend all lectures in person this year.”

In an last year, Professor Malan had questioned the value of saying everyone should attend every lecture.

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"Sitting in Sanders Theater, beautiful though it may be, has never been a particularly effective way to learn complex material," Malan wrote. "Indeed, insofar as the material within a lecture tends to be cumulative, whereby example ‘i’ assumes an understanding of example ‘i-1’, it’s all too easy for a student to miss or misunderstand some detail, the result of which is a suboptimal experience in that lecture thereafter.”

He added: “Sometimes we all just need a moment for something to sink in. If only there were a way to pause or rewind! Simple though those features may be, I daresay we’ve been nearing the point for some time whereby it’s a better educational experience to watch CS50’s lectures online than attend them in person.

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“Indeed, with pause and rewind buttons accompanied by searchable full-text transcripts of lectures, variable playback speed and hyperlinks to related resources, all of which lend themselves to more active engagement with the course’s lectures, it’s hard to argue that sitting and listening live in a theater is better."

Last year, Professor Malan recorded the lectures a few days in advance of the live class session, so that students could have access in advance, if they wanted. And he made clear that this was an acceptable way to learn the material covered in each lecture.

In an email to Inside Higher Ed, Professor Malan said that there was no decline in learning outcomes in the course, even as the number of students who attended lectures in person was not as high as in past years.

Professor Malan also said that he realised that there will still be students who have scheduling conflicts with other courses such that they may rely on the recordings, which will be produced live this year. And other students may benefit from watching the recordings after attending the lectures in person.

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So why revert to telling students they are expected in class?

“Enough former students reported that something was missing, not just the students themselves but the energy of an audience, that we decided to bring [encouraging students to attend] live lectures back this fall,” Professor Malan said.

This is an edited version of a story that .