Chimpanzees and language: why science regretted sign experiments
On July 21, 2026, the story of the last two chimpanzees remaining from pioneering sign language research, Tatu and Loulis, continues to fascinate and raise discussions. Today living in a sanctuary in Canada, these primates represent the culmination of a period of great scientific enthusiasm, but also of complex ethical dilemmas that have led many researchers to reevaluate their approach to animals. The communication capacity of these animals, which master a considerable vocabulary in American Sign Language (ASL), contrasts with the closure of the ambitious projects that gave rise to them.
The search for communication and initial experiments
Curiosity about the possibility of animals communicating using human language has captivated scientists and linguists for centuries. In the 1960s, research gained new impetus with the emergence of serious studies focused on chimpanzees, primates that have a remarkable genetic proximity to humans. The hope was to uncover whether language, in essence, was a characteristic exclusive to the human species or whether other animals could master it under the right conditions.
The pioneers in this area were psychology professors Allen and Beatrix Gardner of the University of Nevada, Reno. They were convinced that chimpanzees could learn human language if they were raised in a suitable environment. Instead of focusing on speech, which is anatomically difficult for chimps, the Gardners chose to teach them American Sign Language, a method that has shown promise.
Washoe’s pioneering of sign language
In 1966, the Gardners adopted a baby chimpanzee, Washoe, who had been brought from West Africa by the U.S. Air Force for research purposes. Washoe was raised very similarly to a human child, learning habits such as using the toilet and playing with dolls. She quickly demonstrated an impressive ability to sign language, learning 245 words before her death in 2007 at Central Washington University. His story mobilized the academic world and aroused the interest of other scientists.
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The experiments were extended to four other chimpanzees: Moja, who expressed great interest in painting; Dar, known for liking to wear hats and examine machines; Pili, who unfortunately died young; and Tatu. Later, supervision of these projects was transferred to Roger Fouts and his wife, Deborah Fouts, former students of the Gardners, who also cared for Loulis, the only chimpanzee to learn sign language directly from other chimpanzees.
Ethical dilemmas and scientific controversy
Despite the apparent success of the first experiments, the 1970s brought a new wave of questions, especially with studies involving the gorilla Koko and the chimpanzee Nim Chimpsky. The methods applied to these animals have generated heated debates about primates’ true understanding of language. Critics argued that the observed “language” could be more a form of operant conditioning than a genuine capacity for semantic and syntactic use, as in humans.
This period marked a turning point in primatology, raising serious ethical concerns about raising wild animals in such artificialized environments. The inability to reintegrate these primates into their natural habitats or into complex social groups outside the laboratory has become a dilemma. Many scientists began to question whether the benefits of the knowledge acquired justified the cost of a lifetime in captivity and the artificiality of their existence. The “regret” of some researchers reflects this profound reevaluation of the limits and responsibilities of science in relation to animal life.
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Tatu and Loulis’ current life at the sanctuary
Tatu and Loulis, the last survivors of these early experiments, spent much of their lives at research institutions in Oklahoma and Washington. Since 2013, they have resided in Canada, at a sanctuary run by the non-profit Fauna Foundation, where they continue to use sign language with their keepers. His current routine offers a contrast to the laboratory environment, prioritizing well-being and the continuity of his interactions.
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The two chimpanzees developed distinct vocabularies and communicative preferences:
- Armadillo:The female, aged 49, is the most expressive, using 215 words in ASL. Their most frequent requests are for foods such as cheese, coffee and tea.
- Louis:The 47-year-old male has mastered 78 words in ASL. He often asks keepers to play tag, demonstrating a more playful side to his communication.
The lasting legacy in understanding animal intelligence
The story of Washoe, Tatu, Loulis and other chimpanzees who learned sign language left a complex but undeniable legacy for science. Although initial enthusiasm for a “human language” in animals was tempered by rigorous analysis and ethical debate, these studies have significantly expanded understanding of primate cognition and communication capabilities.
Pioneering research into sign language challenged the anthropocentric view of language, encouraging greater attention to animal intelligence and the diverse forms of communication that exist in nature. The outcome of these projects, with reflection on the impact on animals’ lives and the change in ethical standards, serves as an important reminder of the responsibility of scientific research. The existence of Tatu and Loulis today is a living testimony to this journey, marking an era of discoveries and reevaluations in the relationship between humans and other great primates.
