In the quiet hills of Woodside, California, a remarkable relationship between species unfolded that would forever change our understanding of non-human intelligence. Koko, a western lowland gorilla born at the San Francisco Zoo in 1971, became the centerpiece of one of the most fascinating interspecies communication studies in history. Through her remarkable ability to learn and use American Sign Language, Koko challenged long-held assumptions about the cognitive abilities of great apes and the dividing line between humans and other animals. Her story is not just about a gorilla who could “talk,” but about how one ape’s life opened new windows into animal consciousness, emotional complexity, and the ethical considerations of how we treat our closest evolutionary relatives.
The Birth of Project Koko
Project Koko began in 1971 when Francine “Penny” Patterson, then a Stanford University graduate student, initiated a language acquisition study with the one-year-old female gorilla. Patterson had been inspired by earlier research with chimpanzees and wanted to explore whether gorillas—often considered less intelligent than chimps—could also acquire language. What began as a limited four-year experiment evolved into a lifelong commitment and one of the longest-running interspecies communication studies in history.
The project faced initial skepticism from the scientific community, with many researchers doubting that gorillas possessed the cognitive capacity for language. However, Patterson’s perseverance and Koko’s apparent aptitude for sign language quickly began yielding results that challenged these assumptions. Within just a few years, Koko had acquired dozens of signs and was combining them in ways that suggested rudimentary syntax, not just mimicry. This early success established the foundation for what would become a groundbreaking exploration of ape cognition.
Koko’s Linguistic Achievements
By the time of her death in 2018 at age 46, Koko had reportedly learned over 1,000 signs in American Sign Language and could understand approximately 2,000 words of spoken English. While controversy exists among linguists about the true extent of her language comprehension, there’s little doubt that Koko demonstrated an impressive ability to communicate. She could form requests, express emotions, describe objects, and even engage in simple conversations. Perhaps most remarkably, she demonstrated the ability to combine signs in novel ways to express new concepts—creating “water bird” for a duck or “finger bracelet” for a ring.
Koko’s vocabulary acquisition followed patterns similar to those observed in children learning language, albeit at a slower pace. She showed preferences for certain topics, demonstrated humor, and even engaged in wordplay. Patterson documented instances where Koko would deliberately sign incorrect answers as a joke, then laugh at her own mischief. These behaviors suggested not just rote learning but a more complex understanding of language as a tool for social interaction. Though scientists continue to debate whether Koko truly understood syntax and grammar, her accomplishments significantly expanded our understanding of apes’ language capabilities.
Emotional Intelligence and Empathy
Perhaps more profound than Koko’s linguistic abilities was the emotional depth she displayed throughout her life. Koko exhibited a range of emotions that many had previously considered uniquely human. She expressed joy, sadness, anger, regret, and even grief. In one of the most famous examples of her emotional complexity, Koko reportedly mourned deeply upon learning about the death of her kitten All Ball, signing “sad” and “cry” when told the news. This response challenged the notion that complex emotional experiences like grief were exclusive to humans…