When seesaws and tall slides and other perils were disappearing from New York’s playgrounds, Henry Stern drew a line in the sandbox. As the city’s parks commissioner in the 1990s, he issued an edict concerning the 10-foot-high jungle gym near his childhood home in northern Manhattan.

“I grew up on the monkey bars in Fort Tryon Park, and I never forgot how good it felt to get to the top of them,” Mr. Stern said. “I didn’t want to see that playground bowdlerized. I said that as long as I was parks commissioner, those monkey bars were going to stay.”

His philosophy seemed reactionary at the time, but today it’s shared by some researchers who question the value of safety-first playgrounds. Even if children do suffer fewer physical injuries — and the evidence for that is debatable — the critics say that these playgrounds may stunt emotional development, leaving children with anxieties and fears that are ultimately worse than a broken bone.

“Children need to encounter risks and overcome fears on the playground,” said Ellen Sandseter, a professor of psychology at Queen Maud University in Norway. “I think monkey bars and tall slides are great. As playgrounds become more and more boring, these are some of the few features that still can give children thrilling experiences with heights and high speed.”