Harold W. Stevenson, 80, a developmental psychologist whose comprehensive studies in the 1980s showed that schoolchildren in Asia outperformed American children often because they simply worked harder, died of pneumonia July 8 at the Veterans Administration Hospital in Palo Alto, Calif.

Dr. Stevenson's surveys for the Center for Human Growth and Development at the University of Michigan were the first to show that from their earliest school years, U.S. children lagged behind students in Japan and Taiwan in reading and math. The reasons cited were multiple, but one finding stood out: U.S. kindergartners, first-graders and fifth-graders did less homework, spent fewer school hours studying and wasted more classroom time.

"The Japanese and Chinese believe that people are basically the same and that the difference between success and failure lies in how hard you work," Dr. Stevenson said in 1987. "Americans give more importance to native ability, so they have less incentive to work hard in school."

The findings startled Americans who assumed that mathematics skills, particularly, were connected to genetics or intelligence. Dr. Stevenson found no such link. U.S. students, he said, actually started school with certain advantages, but after they entered grade school, parents turned their children's education over to the schools while Asian parents continued to be involved with the children's homework and tutoring. Parents in the United States also were more easily satisfied with the quality of education than were Asian parents, he found.

Dr. Stevenson's work also illuminated the different methods of teaching in Asia that emphasized clear goals, carefully planned lessons and creative problem-solving. Mixing high achievers and low performers in classes, as the Japanese and Taiwanese did, tended to improve the performance of the low achievers, he found.

His influential work was cited often during the early 1990s, as Americans realized their schools and students were no longer the best in the world. His studies were built on hundreds of hours of classroom observation in Minneapolis; Sendai, Japan; and Taipei, Taiwan. Later research included schools in mainland China.

"When his data from China itself began to come out, it was really sobering because we're talking about kids who didn't have many physical resources, who were poor and in schools with dirt floors . . . yet these kids were doing remarkably well," said John Hagen, a Michigan psychology professor and executive officer of the Society for Research in Child Development.

Dr. Stevenson was born in Dines, Wyo., and his early education was in a one-room schoolhouse.

During World War II, he served in the Navy, learning Japanese and beginning a lifelong interest in Asian cultures. After the war, he graduated from the University of Colorado, then received a master's degree and a doctorate in psychology from Stanford University in 1951.

Dr. Stevenson helped found nursery schools in Texas, Minnesota and Michigan that were designed so graduate students in education and psychology could observe children in a school setting. In the early 1950s, he and his wife, clinical psychologist Nancy Guy Stevenson, established All-Austin Nursery School, one of the country's first racially integrated preschools, in Austin.

In the 1960s, he was director of the Institute of Child Development at the University of Minnesota. In 1971, he joined the University of Michigan in Ann Arbor.

James W. Stigler, who co-wrote "The Learning Gap: Why Our Schools Are Failing and What We Can Learn From Japanese and Chinese Education" (1992), noted that Dr. Stevenson made a rare pivot in his professional research in the 1970s, moving from his former specialty in children's behavioral studies to the examination of cross-cultural educational methods.

In 1973, Dr. Stevenson was with the first delegation of foreign researchers allowed to visit China since the 1940s. He then began a series of cross-cultural studies of children's academic achievement in the United States, Asia, Latin America and Eastern Europe.

That work brought many honors, but his goal was to influence the social and educational policies of the country, his wife said.

By many accounts, Dr. Stevenson was a man who found learning fascinating and joyful. One of his daughters, Janet B. Zimmerman of Plymouth, Mich., said that his enthusiasm for learning was infectious and that she vividly recalled him helping her with homework.

"Whenever we were stuck in any subject, he would gladly step forward and, with extreme patience, try to help us understand," she said. He would help his children look at problems in multiple ways, regarding mathematics as a series of puzzles to solve, she said.

He repeatedly edited his own work and speeches to make his points as clearly as possible, she said. A colleague of his told her of a time when he walked into a lecture hall where Dr. Stevenson was giving a speech. Behind the rapt audience stood a janitor who was just as fascinated, he said. The next day, the colleague overheard the janitor describing what he had learned to the rest of the custodial staff. That, Zimmerman said, was the type of communication her father sought. "He would present with equal enthusiasm to custodial staff, to me as a 10-year-old or to the most studious graduate student," she said.

Dr. Stevenson retired in 2001. He had dementia. He and his wife moved from Michigan to Palo Alto in May.

In addition to his wife and daughter, survivors include three other children, Margaret Stevenson of Palo Alto, Andrew Stevenson of Charlottesville and Patricia A. Stevenson of Chicago; a brother; and seven grandchildren.

Harold Stevenson studied why Asian students did better than U.S. pupils.