Can animals learn language?
Early projects: Gua (1930s) and Viki (1950s)
Raised chimpanzees just like human children, in order to see if they would acquire language in a similar way.
Confound: expected chimps to be able to make human vocalizations.
Unfortunate reality: chimpanzees are not physically equipped to make human-like vocalizations, and do not generally show a tendency to make vocalizations anyhow.
Results: the projects were generally unsuccessful. The Gua project was abandoned after nine months; Viki could only speak three words after three years of training.
New twists: Washoe (60s and 70s)
Washoe was also raised just like a human child but was not expected to pick up a system of human vocalizations.
Instead, Washoe's "parents" used American Sign Language in the hopes that she would pick up a human system of gestures.
This project was much more successful. After five years, Washoe had acquired 132 signs (according to some very strict production criteria).
Did Washoe acquire a grammatical system?
Interesting anecdotal evidence: Washoe once dubbed a swan a "water bird".