CAMBRIDGE, Mass. — B.F. Skinner, one of the century’s leading psychologists who believed human behavior could be engineered to build a better world, has died of leukemia. He was 86.

Skinner died Saturday at Mount Auburn Hospital in this university city, a hospital administrator said.

He was the patriarch of the school of thought known as behaviorism and the inventor of the “Skinner box,” a tool he used to demonstrate his theory that rewarded behavior is repeated.

While remembered by many — and sometimes scorned — for teaching pigeons to play pingpong and guide missiles, his novel “Walden Two” was required reading for a generation of college students in the 1960s and 1970s.

Burrhus Frederic Skinner — B.F. to the world, Fred to his friends — spent most of his career at Harvard, where he applied his observations of animals to the motives and manipulation of human conduct.

Skinner’s views were based on his principle of “operant behavior,” the idea that seemingly spontaneous action is regulated through rewards and punishment. People don’t shape the world, he said, the world shapes them.

In the months leading up to his death, Skinner was preparing a defense of his research, which explored the uses of positive and negative reinforcement to improve human behavior.

“I will be dead in a few months,” he said in an interview last month. “But it hasn’t given me the slightest anxiety or worry or anything; I always knew I was going to die.”

Skinner believed that human behavior is predictable, just like a chemical reaction. Since people were run through their paces by their environment, “behavioral technology” could put them to work to create a happy and safe world, free of overpopulation, war and pollution.

Many psychologists disagreed with his theories. Of his contemporaries, Skinner once said, “I can mention only one or two who really very seriously changed their attitudes toward the study of behavior as a result of anything I have ever done or said.”

But his application of the ideas of the Russian physiologist Ivan Pavlov left an indelible stamp on American society. Parents use his “operant conditioning” each time they praise a behavior they want and punish one they don’t want.

Skinner, in his later years a lean man with a fine-featured, patrician face beneath a broad expanse of forehead, was born March 20, 1904, in Susquehanna, Pa., the elder son of Grace Burrhus, an amateur musician, and William Skinner, a lawyer.

After majoring in English at Hamilton College in Clinton, N.Y., Skinner decided he wanted to be a writer. He sent some short stories to the poet Robert Frost, who wrote back: “You are worth twice anyone else I have seen in prose this year.”

Skinner went to Manhattan’s Greenwich Village to work on his craft but after a year or so gave it up. “I discovered the unhappy fact that I had nothing to say,” he recalled, “and went on to graduate study in psychology, hoping to remedy that shortcoming.”

He was attracted to the work of John B. Watson, the founder of behaviorism, and earned his doctorate from Harvard in 1931. He taught at the University of Minnesota and Indiana University before joining the Harvard faculty in 1947.

It was at Harvard that he devised the Skinner box, a soundproof enclosure with buttons or levers that animals press to receive food in return for doing whatever the experimenter wants them to do.

The box provides a precise way to observe, record and measure behavior. It is widely used by psychologists, many of whom are not Skinnerians, as well as by drug researchers, who watch the way animals react to new medicines.

Skinner preferred to call his invention an “operant conditioning apparatus.” He employed it to teach rats, and later pigeons, to perform amazing tricks. Birds learned to play the piano, walk in figure eights and dance.

Table tennis, though, might have carried things too far. Asked once what he would do differently if given the chance, he replied:

“Just one thing. I performed one experiment that has never ceased to reverberate. I’ve been laughed at by enemies and kidded by friends. If I could do it all over again, I’d never teach those pigeons to play pingpong.”

During World War II, he rigged up a way for a pigeon to guide a missile to its goal by pecking on an image of the target when it appeared on a screen. The government never adopted the method.

In the 1940s, Skinner also invented something he thought could revolutionize child rearing — his air crib, known less reverently as the baby box.

The crib was a roomy, insulated, temperature-controlled box with a window. Inside, the baby could sleep and play comfortably without blankets or clothes. Skinner’s younger daughter, Deborah, was raised in an air crib for 2 1/2 years. But like the pigeon-run missiles, it never caught on.

After his retirement in 1974, Skinner maintained an office at Harvard, walking the 2 1/2 miles each day from his Cambridge home. He also spoke occasionally at scientific societies, and in 1982 gave the American Psychological Association a report on how to cope with the frailties of age: Build a stimulating environment, create memory tricks, work less and rest the mind between intellectual workouts.

Skinner is survived by his daughters, Deborah Buzan and Julie Vargas, and his wife, Yvonne.