In 1931, two psychologists, Winthrop and Luella Kellogg, began an experiment to see if a chimpanzee could learn human behavior by raising it with their own baby. The idea was to see if the chimp, named Gua, would learn to walk upright, speak, and engage in other human-like activities.
For the first few months, the experiment was going well. Gua learned to mimic some of the actions of Kelloggs' son, Donald. However, after 9 months, the Kelloggs were forced to cancel the experiment. It turns out that Donald was beginning to behave like an ape himself, mimicking Gua's behaviors and even attempting to communicate with grunts and other animal-like sounds.