It allows the better students in the class to help teach the others—and everyone benefits in the process, he said, citing research from Carnegie Mellon University and elsewhere that suggests peer instruction can lead to better retention.

Mazur demonstrated the process with conference attendees, using a typical problem he might pose to his physics students.

After briefly explaining why metal expands when it’s heated—the atoms move more vigorously, and so they spread out because need more space in which to move—he asked attendees to imagine a rectangular piece of metal with a circular hole in the middle: Would the diameter of the hole increase, decrease, or stay the same if the metal were heated uniformly?

Participants logged their responses, and then they huddled to confer with their colleagues. Those who thought the hole would shrink explained that the atoms in the metal around the edge of the hole would want to move away from the atoms in the rectangle’s interior, thereby contracting the hole.

But others correctly argued that the atoms around the hole’s edge would not move toward the hole’s center, because that would create even more crowding among themselves; instead, those atoms would move away from the hole’s center in an attempt to create more space for themselves, thereby expanding the circle’s diameter.

When Mazur posed the question a second time, the number of correct responses nearly doubled as a result of this discussion. And when he shared the correct answer, many attendees affirmed they’ll remember this concept much more vividly for having participated in the discussion.

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