Washoe became pregnant several times, but none of her pregnancies was successful. In the 1970s, she was given an adoptive son, Loulis. The researchers at CHCI decided that none of the caretakers would sign when Loulis was there except to use the key seven signs who, which, want, where, name, that and sign. This meant that Loulis would only be able to acquire language if it was taught to him by the other chimpanzees. Remarkably, Loulis nonetheless acquired more than 50 signs just by watching the other chimps, mirroring the manner in which human children acquire language.
Another study on animla language was carried out by Terrace (1979…