Donald Triplett, ‘Case 1’ in the Study of Autism, Dies at 89

Donald Triplett, who as a child was “Case 1” in the history of autism diagnosis and as an adult became an influential case study in how people with autism can find fulfillment, died on Thursday at his home in Forest, a small city in central Mississippi. He was 89.

The cause was cancer, his nephew, O.B. Triplett, said.

The prevalence of autism diagnoses has been rising for decades. In 2006, about one in 110 children was said to have the condition. This March, the figure was one in 36, according to the Centers for Disease Control and Prevention.

What has caused this rise is a matter of debate. What is clear is that the modern understanding of autism can be traced to events in Mr. Triplett’s childhood.

Donald Gray Triplett was born in Forest on Sept. 8, 1933, to Mary (McCravey) Triplett, a high school English teacher whose family owned the local bank, and Beamon Triplett, a lawyer who had been educated at Yale Law School.

Don seemed to live in a world apart from his family and the rest of society. He was unresponsive to other children, to a man dressed as Santa Claus, even to his mother’s smile.

He used language in ways that suggested private meanings, assigning numbers unaccountably to the people he met and repeating mysterious phrases like “I could put a little comma or semicolon” and “through the dark cloud shining.”

He had a mania for other repetitive behaviors, including spinning round objects like cooking pans. If any of his various rituals was interrupted, he threw destructive temper tantrums.

He had skills that were equally baffling to those around him. He could answer without hesitation the result of multiplying 87 by 23. He could sing songs with perfect pitch after hearing them only once. A rumor went around that he had calculated the number of bricks in the facade of his high school just by glancing at it.

In August 1937, Don’s parents sent him to a state-run children’s facility in a Mississippi town called Sanatorium. They visited just twice a month, and Don was reported to spend his days listlessly, sometimes even motionless.

It was common at the time for children with serious psychological issues to be permanently institutionalized. But after about a year, Don’s parents insisted that they wanted him to return home. They soon brought him to a doctor in Baltimore named Leo Kanner.

Dr. Kanner had founded the first child psychiatry clinic in the United States at Johns Hopkins University. Initially, he did not know how to describe Don’s condition.

A Galician immigrant who had studied in Berlin, Dr. Kanner would have been familiar with the concept of “autism” developed by the Swiss psychiatrist Eugen Bleuler, who in the years before World War I used it as a term for the total self-absorption of some schizophrenia patients.

In a 1943 paper titled “Autistic Disturbances of Affective Contact,” Dr. Kanner described case studies of 11 children that, he said, illustrated a condition that differed “markedly and uniquely from anything reported so far” in the annals of psychology.

With Don as the inaugural case — he is referred to as “Case 1” and “Donald T.” — Dr. Kanner sketched a disorder that included obsessive repetitive habits, “excellent rote memory” and an inability to relate “in the ordinary way” to other people. He called this form of autism “rare” but added that it was “probably more frequent than is indicated by the paucity of observed cases.”

That paper — along with copious notes taken by Beamon Triplett describing his son’s condition to Dr. Kanner — became the foundation of what is known today as autism spectrum disorder. Its official description by the C.D.C. and in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders still sounds reminiscent of Dr. Kanner’s 80-year-old theorizing.

As he got older, Donald Triplett never stopped having obsessions, speaking mechanically and struggling to hold a conversation. But his life also took a trajectory that would have seemed unimaginable when he was an institutionalized 4-year-old.

He graduated not only from high school but also, in 1958, from Millsaps College in Jackson, Miss., where he joined the Lambda Chi Alpha fraternity and studied French and math.

Skills that he lacked as a teenager, he gained in his 20s and 30s. He learned how to drive, for instance, and got around using a Cadillac of his own. He took a job as a bookkeeper at the local Bank of Forest, of which his grandfather had been a founder. With the help of a travel agent in Jackson, he managed to take vacations by himself to countries around the world.

His remarkable self-sufficiency became a national story thanks to the journalists John Donvan and Caren Zucker, who wrote an article about Mr. Triplett’s life for The Atlantic in 2010. That article led to a book, “In a Different Key: The Story of Autism,” which was a finalist for the 2017 Pulitzer Prize in general nonfiction, and a documentary of the same title that aired on PBS last year.

Mr. Donvan and Ms. Zucker drew several conclusions from Mr. Triplett’s story, including that his family’s wealth and social status had been crucial in helping him secure a decent life. But they emphasized above all the importance of Mr. Triplett’s hometown and its roughly 3,000 people.

The community of Forest, they wrote for the BBC’s magazine in 2016, “made a probably unconscious but clear decision in how they were going to treat this strange boy, then man, who lived among them.”

“They decided, in short,” they added, “to accept him.”

Mr. Triplett remained close with his brother, Oliver, who facilitated his interactions with journalists. Oliver Triplett died in 2020. No immediate family members survive.

But he did have many friends. Some of them, a group of men, joined Mr. Triplett outside Forest’s City Hall for coffee every morning. Neighbors decades younger than he was welcomed him on their team for the Forest Country Club golf tournament — and he played respectably. People spoke admiringly of his skills in music and math, even to the point of exaggerating how much of a savant he was.

On three occasions during their reporting, Mr. Donvan and Ms. Zucker wrote in The Atlantic, residents of Forest gave them a warning in strikingly similar language: “If what you’re doing hurts Don, I know where to find you.”

One friend of his put it this way: “Don’s got some odd behaviors and some eccentricities, but he’s our guy.”