Endel Tulving, whose insights into the structure of human memory and the way we recall the past revolutionized the field of cognitive psychology, died on Sept. 11 in Mississauga, Ontario. He was 96.
His daughters, Linda Tulving and Elo Tulving-Blais, said his death, at an assisted living home, was caused by complications of a stroke.
Until Dr. Tulving began his pathbreaking work in the 1960s, most cognitive psychologists were more interested in understanding how people learn things than in how they retain and recall them.
When they did think about memory, they often depicted it as one giant cerebral warehouse, packed higgledy-piggledy, with only a vague conception of how we retrieved those items. This, they asserted, was the realm of “the mind,” an untestable, almost philosophical construct.
Dr. Tulving, who spent most of his career at the University of Toronto, first made his name with a series of clever experiments and papers, demonstrating how the mind organizes memories and how it uses contextual cues to retrieve them. Forgetting, he posited, was less about information loss than it was about the lack of cues to retrieve it.
He established his legacy with a chapter in the 1972 book “Organization of Memory,” which he edited with Wayne Donaldson.
In that chapter, he argued for a taxonomy of memory types. He started with two: procedural memory, which is largely unconscious and involves things like how to walk or ride a bicycle, and declarative memory, which is conscious and discrete.
Those distinctions were already well known and uncontroversial. But then he further divided declarative memory into two more types: semantic, meaning specific facts about the world, like where France is and who George Washington was, and episodic, meaning personal memories of past experiences.
Dr. Tulving was especially interested in episodic memory, which is, by its nature, subjective and unique to each of us. For precisely those reasons, it is central to how we make sense of the world and our place within it — in other words, human consciousness.
Episodic memory was not just about the past, Dr. Tulving said; it was also critical to our ability to conceive of our future. That’s because when we think about past events, we don’t think about them the same way we do about learned facts. Through our capacity for episodic memory, we relive the events in our mind, what he called “mental time travel.” That same capacity allows us to imagine ourselves in the future, too.
For that chapter alone, Dr. Tulving is considered one of the leading cognitive psychologists of the 20th century.
“In terms of people studying human memory, both from a psychological perspective and a neuroscience perspective, he would be right up at the very top,” Henry Roediger, a professor of psychology at Washington University in St. Louis, said in a phone interview.
Dr. Tulving’s distinction between semantic and episodic memory rapidly reshaped the field of cognitive psychology. But skeptics questioned whether it actually reflected the way the mind works or was merely a useful theory.
Dr. Tulving demonstrated that the distinction was more than just a handy intellectual framework through a series of interviews in the 1980s with an amnesiac patient named Kent Cochrane.
Mr. Cochrane had lost his capacity for episodic memory, though his semantic memory was intact. He could explain in detail how to change a car tire, but he could not remember whether he had ever changed one himself, or when he learned to. He was a decent chess player, but he could not recall if he had ever played. Nor could he imagine what he would be doing the next day.
Dr. Tulving asserted that episodic memory is unique to human beings; animals might exhibit episodic-like memory, he said, but there was no evidence that they experienced such memory in the same way humans do — what he called autonoetic consciousness.
“When one thinks today about what one did yesterday, time’s arrow is bent into a loop,” he wrote in the Annual Review of Psychology in 2002. “When Mother Nature watches her favorite creatures turning one of her immutable laws on its head, she must be pleased with her own creativity.”
Endel Tulving was born on May 26, 1927, in Petseri, a city in southeast Estonia later annexed by the Soviet Union and known today by its Russian name, Pechory. His father, Juhan, was a judge, and his mother, Linda (Soome) Tulving, owned a furniture store.
He was still in school when the Germans occupied Estonia during World War II. Amid the chaos following the German retreat in 1944, he was separated from his parents and ended up in an American-run displaced persons camp, where he worked as a translator. It would be more than 20 years before he saw his parents again.
He finished high school in the camp and briefly studied medicine at the University of Heidelberg in Germany before immigrating to Canada in 1949. While still in Germany he had been hired to tutor a young Estonian refugee named Ruth Mikkelsaar; the two married in 1950.
Ruth Tulving died in 2012. In addition to his daughters, Dr. Tulving is survived by five grandchildren.
He received a bachelor’s degree in 1953 and a master’s degree in 1954 from the University of Toronto, both in psychology. He received his doctorate in psychology from Harvard in 1957.
He then returned to Toronto, where, aside from a few years teaching at Yale in the early 1970s, he spent his entire career. He taught at the university until 1992, when he moved to the Rotman Research Institute, also in Toronto.
Rather than settling into a sinecure, he undertook a new line of research. The institute had recently received a positron emission tomography scanner, which allowed him and his colleagues to monitor brain waves while conducting experiments.
As subjects performed a variety of recall tasks, he was able to see different parts of the brain light up — one set of areas for semantic memory, another for episodic. He and his colleagues proudly reported their results in a landmark 1994 paper.
Technology had finally caught up to, and proven, the insights that Dr. Tulving had first ventured, more than 20 years before.