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 . research in psychology at Stanford University. The zoo agreed as long as Penny agreed to make at least a "4-year" commitment.