Open this photo in gallery In an undated handout image, the primate researcher Dorothy Cheney sits with baboons at the Moremi Game Reserve in Botswana. HANDOUT/Handout via The New York Times

Dorothy Cheney, whose careful research into how primates live and communicate revealed the surprising complexity of their thought processes and social structures, died on Nov. 9 at her home in Devon, Pa. She was 68.

Her husband and research partner, Robert Seyfarth, said the cause was breast cancer.

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“Cheney was a spectacular scientist,” Robert Sapolsky, a professor of biology and neurology at Stanford University and the author of books such as A Primate’s Memoir, said by e-mail. “Along with Robert Seyfarth, she did wonderfully clever, elegant field experiments that revealed how other primates think about the world – showing that they think in far more sophisticated and interesting ways than people anticipated.”

Rather than doing their research in laboratories, Dr. Cheney and Dr. Seyfarth spent long stretches in the wilds of Africa and elsewhere, studying gorillas, baboons, vervet monkeys and other animals.

One of their best-known experiments, conducted in Kenya in 1977, showed that vervets made distress sounds to convey a specific message about a given threat. They hid loudspeakers in bushes, played recorded sounds of vervets and watched the reaction. A particular bark sent the animals scurrying up trees because it was a warning about leopards; a low-pitched staccato noise had them looking skyward for predatory eagles.

They summarized their research in their first book, How Monkeys See the World: Inside the Mind of Another Species (1990).

Later research in Botswana included insights into the hierarchical nature of baboon societies and its possible evolutionary effects.

“Because Western scientists learned about primates by examining corpses or observing single animals brought home as pets,” they wrote in their 2007 book, Baboon Metaphysics: The Evolution of a Social Mind, “few if any ever learned what can be discovered only through long, patient observation: that the most human features of monkeys and apes lie not in their physical appearance, but in their social relationships.”

Dorothy Leavitt Cheney was born Aug. 24, 1950, in Boston. Her father, Edward, was a Foreign Service officer, and her mother, Sally (Leavitt) Cheney, was a translator.

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Dr. Cheney spent parts of her childhood in Malaysia, Holland, India and Nicaragua. She graduated from Abbot Academy in Massachusetts in 1968 and earned a bachelor’s degree in political science at Wellesley College in 1972.

She had planned to go to law school. But her husband had applied to work with the noted zoologist Robert Hinde at Cambridge University, and when he had an opportunity to go to South Africa to study baboons, he suggested she come along.

“I thought, ‘What the hell, this could be fun for a year or two,’ so I decided to put off law school and join him,” she said in an interview for Proceedings of the National Academy of Sciences. “It was a transformative experience.”

After 18 months, she applied to study with Prof. Hinde as well. She received a PhD in zoology at Cambridge in 1977.

She and her husband were assistant professors at Rockefeller University in New York, then in 1981 joined the faculty at the University of California, Los Angeles. In 1985, they moved to the University of Pennsylvania, where, at her death, Dr. Cheney was a professor of biology.

Dr .Seyfarth, in an e-mail interview, said theirs was not one of those partnerships in which each person had a defined role.

“Our scientific contributions are hard to separate because the genesis of our ideas and experiments quickly became lost in the mists of conversation,” he said. “One of us had an idea, the other critiqued it, and back and forth it went until it finally took shape and neither of us remembered or cared who took credit for what.”

In addition to her husband, Dr. Cheney leaves her daughters, Caroline Cheney Roberts and Lucia Hall Seyfarth; three siblings; three step-siblings; and a granddaughter.