“I’ve slowed down for sure,” he says, noting that it is possible to stay productive past 70, “for a short while.”

Mansfield says that without the law, professors might not recognize the advent of senility.

“It’s part of senility to not believe it when it’s happening to you,” Mansfield says. “Being old is not great. Things start to go wrong and you don’t always notice it.”

Klemperer shares Mansfield’s concern.

“It’s very hard to tell how doddering you are,” he says.

Lyman Professor of Biology Andrew Biewener agrees with Mansfield that the majority of professors accomplish their most innovative work earlier rather than later.

“I think in any field age brings a certain perspective and wisdom,” Biewener says. “But as you move along in age you are less and less able to do the daily research activity.”

Some students say they have similar concerns about the productivity of older professors.

Sarah G. Heyward ’06 says her freshman seminar, taught by a professor older than 70, was both a positive and negative experience.

“I took no notes because nothing was ever really said—he left everything in our hands,” she says. “Some people complained that he didn’t really know any of our names or anything. It wasn’t a bad class, it was just sort of ridiculous at times,” Heyward says.

But she says she valued his individual advice.

“I found him really nice and very helpful when I met with him outside of class, to brainstorm paper ideas or something,” she says. “But during class he sort of just let us talk and then when he talked it was almost always just stories about his…interesting life.”

Ari D. Brettman ’04, a history of science concentrator, says that in his experience, older professors tend to teach large lecture courses, while the younger crowd work more on their own work.

“I suspect that when the older professors teach it’s because they want to,” Brettman says. “Younger professors, especially ones who haven’t made tenure yet, are generally more concerned with succeeding in the laboratory and achieving eminence in research than succeeding in the lecture hall. The older profs have already made a name for themselves and, perhaps, have more time and greater inclination for teaching.”

“Dead Wood”