Vicki (chimpanzee)

Viki was the subject of one of the first experiments in ape language. Viki was raised by Keith and Catherine Hayes in the same manner as a human infant, to see if she could learn human words. She was given speech therapy, which involved the Hayeses (her adoptees) manipulating her lower jaw. Eventually, she was able to voice four words:

This extremely limited success was at first interpreted as evidence that apes were not capable of using human language. However, further experiments in which chimpanzees were instructed in the use of American sign language indicated that Viki's achievements had been significantly hampered by physiological limitations—chimpanzees are not able to produce the sounds that make up human speech.

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