Scientific Goals & History

Scientific Goals

The original goal of Project Koko was to see if it was possible to teach gorillas sign language and, if so, how much we could learn about their cognitive abilities through direct communication. This goal, which to a large extent has been achieved, has evolved to include other forms of communication, and the focus has shifted from pure scientific inquiry to producing benefits for great ape welfare, education, and conservation, using scientifically validated methods.

History and Context

Koko was born in the San Francisco Zoo in 1971 and spent the first six months of her life in the nursery of the children’s zoo behind a glass window where the public could see her and where Penny Patterson, then a Stanford graduate student, met her. From age six months to one year Koko was critically ill and moved to a trailer on zoo property. Penny began working with Koko when she recovered her health, and requested permission from the zoo to continue working with her as part of her Ph.D. research in psychology at Stanford University. The zoo agreed as long as Penny agreed to make at least a “4-year” commitment.

In 1974 Koko and her trailer were moved to Stanford University where Penny and Dr. Ron Cohn continued to work with her, and they have been together ever since. Michael, a male gorilla, joined Koko in 1976, and in 1979 the whole group moved to Woodside, CA where Ndume, a second male gorilla joined the group in 1991.

In the years since 1971, Penny (Dr. Patterson) has spent her life caring for Koko and the two male gorillas (Michael and Ndume) and has established highly empathic relationships with them that may be difficult to replicate due to the commitment required. A successful program such as this requires using language during daily documented interactions, as well as the ability to “listen” to the gorillas and discern their meanings. Few people have the patience, stamina, and sensitivity to achieve this.

With Penny’s help, Koko has learned to use over 1,000 signs and seems to understand approximately 2,000 spoken English words. Further, Koko understands these signs sufficiently well to adapt them or combine them to express new meanings that she wants to convey.

Gorilla Michael, who grew up with Koko and passed away in the year 2000 at age 27 (of cardiomyopathy), became similarly fluent in sign language, highly proficient at painting, and established that Koko is not unique — such capabilities previously thought to be beyond gorillas and other great apes are now seen as intrinsic.   Ndume has also learned a number of words from both Koko and her caregivers, and studies of zoo gorillas have revealed a natural gestural communication system that appears to be quite complex.

Moreover, other ape language studies have revealed similar capabilities in other great apes. Thus, with over 4 decades of multimedia research data accumulated, and more being collected daily, the challenge is to learn as much from our fellow great apes as possible and to enable the dialogue to continue beyond the scope of “Project Koko” for the benefit of all species concerned.


Gorillas can be stubborn (Koko)
Penny carries young Koko in her backpack