Nicholas Hitchon, whose life was chronicled in the acclaimed “Up” series of British documentaries, beginning when he was a boy in the English countryside in 1964 and continuing through the decades as he grew to become a researcher and professor at the University of Wisconsin, died on July 23 in Madison, Wis. He was 65.

A posting on the university’s website announced his death, from throat cancer. In the most recent installment of the series, “63 Up,” in 2019, he described his struggles with the disease.

Professor Hitchon was a student in a one-room primary school in Littondale, north of Manchester, when a researcher working on a Granada Television project came looking for a 7-year-old willing to participate in what was originally viewed as a one-shot TV special. Young Nick was only 6, but he was talkative and unintimidated by cameras, so he was signed up as one of 14 youngsters to be profiled.

The idea was to get a cross-section of children from Britain’s economic classes, look at their schooling and other experiences and capture their perspectives on the adult world. Nick represented the rural child. He endeared himself to that original television audience with his response to an interviewer who, clearly fishing for cuteness, asked, “Do you have a girlfriend?”

“I don’t want to answer that,” Nick said. “I don’t answer those kind of questions.”

The 1964 film, a simple effort titled “Seven Up!,” directed by Paul Almond, began to transform into documentary greatness when one of his researchers, Michael Apted, picked up the thread at the end of the decade and made a follow-up, “7 Plus Seven,” interviewing the same children.

Mr. Apted, who died in 2019 at 79, directed that and all the subsequent installments, which were made at seven-year intervals. They became a fascinating portrait of ordinary people growing up, changing and reflecting on their lives.

“What I had seen as a significant statement about the English class system was in fact a humanistic document about the real issues of life,” Mr. Apted wrote in 2000.

Over the years, Professor Hitchon expressed both admiration for what the series was accomplishing and discomfort with being a part of it and with the way it was edited.

“I’ve learnt that the stupider the thing I say, the more likely it is to get in,” he told The Independent of Britain in 2012, when “56 Up” was released. “You’re asked to discuss every intimate part of your life. You feel like you’re just a specimen pinned on the board. It’s totally dehumanizing.”

He also thought the filmmakers had a tendency to play up stereotypes of British society, something he said he felt even as a boy in the early installments, when crew members would chase sheep into the camera’s view while filming him.

“These people thought that I was all about sheep,” he told The Chronicle of Higher Education in 2005. “I’m quite fond of sheep, but I was more interested in other things.”

If the series seemed too intent on demonstrating that economic class was a determining factor throughout life, Professor Hitchon — who went from a one-room rural schoolhouse to a Ph.D. and a life of academic accomplishment — proved to be an exception.

“He’s one of the success stories,” Mr. Apted told the education journal in 2005.

William Nicholas Guy Hitchon was born on Oct. 22, 1957, to Guy and Iona (Hall) Hitchon, who had a farm in Littondale. He studied physics at Oxford University, earning a bachelor’s degree there in 1978, a master’s in 1979 and a Ph.D. in engineering science in 1981. Soon after, he left for the United States to teach at the University of Wisconsin, a move that he thought “28 Up” (1984) had wrongly portrayed as abandoning his home country in pursuit of money.

“He took us out to West Towne” — a Madison mall — “and had us walk around over and over again,” Professor Hitchon told The Capital Times of Madison in 1987, speaking of Mr. Apted. “Then he did a voice-over where he talked about that I’d come to America for a salary of $30,000.”

Professor Hitchon pursued research on nuclear fusion, then switched to computational plasma physics. Once in a while, Mr. Apted would ask him about his work.

“When I try to explain,” Professor Hitchon told Physics Today in 2000, “his eyes glaze over.”

He published more than 100 journal articles and three books, the university’s posting said. He retired in 2022.

His first marriage, to Jacqueline Bush, ended in divorce. He married C. Cryss Brunner in 2001. She survives him, along with a son from his first marriage, Adam; and two brothers, Andrew and Chris.

If Professor Hitchon was sometimes uncomfortable with the “Up” project, he stuck with it, while a few of the other original participants dropped out. In “42 Up” (1998), he even joked about its role in his life.

“My ambition as a scientist is to be more famous for doing science than for being in this film,” he told Mr. Apted on camera. “Unfortunately, Michael, it’s not going to happen.”