Great ape language research historically involved attempts to teach chimpanzees, bonobos, gorillas, and orangutans to communicate using imitative human speech, sign language, physical tokens and computerized lexigrams. These studies were controversial, with debate focused on the definition of language, the welfare of test subjects, and the anthropocentric nature of this line of inquiry.

The consensus among linguists remains that human language is unique.

Contemporary research has steered away from attempting to teach apes human language and focuses instead on observing apes' intraspecies communication in zoos and natural habitats. This includes gestures, facial expressions, and vocalizations.

Richard Lynch Garner was the first researcher to explore in depth the communication skills of nonhuman primates. He began in 1884 studying monkeys in American zoos and later travelled to Africa to study gorillas and chimpanzees. He wrote frequently for popular journals and newspapers and ultimately had three books published on the subject, The Speech of Monkeys (1892), Gorillas & Chimpanzees (1896), and Apes and Monkeys: Their Life and Language (1900).

Garner argued that nonhuman primates have their own forms of speech. He claimed to be able to talk to the animals and act as their interpreter. His methods and conclusions were not scientific by any modern definition, but his work was nonetheless significant. For one thing, Garner studied the animals' intraspecies vocalizations, in some cases in their natural habitats. He went to great length to do so, even living inside of a cage himself to observe gorillas in Africa. This was in contrast to later language studies, which separated apes from their conspecifics (peers) and placed them in alien – human – habitats. Second, Garner pioneered the use of recording primate vocalizations and playing them back later for experimental purposes.

The next line of research came out of cross-fostering studies, where chimpanzees were raised in human homes as children. Primatologist Robert Yerkes launched one such project. He recruited Luella and Winthrop Niles Kellogg, scientists at Indiana University, to raise a chimp named Gua alongside their human child, Donald. In The Ape and the Child, the Kelloggs wrote that "it was very clear during the first few months that the ape was considerably superior to the child in responding to human words. She began to react distinctively to separate vocal stimuli within a few weeks after she had entered the human environment."

The Kelloggs noted that Gua made several distinct vocalizations to communicate different needs, and, accordingly, tried to teach her to speak English words. The Kelloggs were building on Yerkes' assertion:

It seemingly is well established that the motor mechanism of voice in this ape is adequate not only to the production of a considerable variety of sounds, but also to definite articulations similar to those of man.