There were some intriguing differences between the two toddlers. While Donald could recognize people by face, Gua came to know them by clothes and smell. And while Donald was the usual human baby pain in the ass, Gua was incredibly obedient and submissive.
But after a few months Gua’s development slowed while Donald’s picked up. Gua’s motor skills continued to surpass his, but she lagged in things like toilet training. And speech never came to her; in fact the experiment was ended one day in March of 1932 when Donald came into the kitchen and made chimp grunts to ask his mother for a cookie. The Kelloggs had discovered that human/chimp co-development cut both ways.
Gua was sent back to the primate center from which she came, and died not long after. Donald made it to the age of 43, and then committed suicide. Winthrop wrote a book called The Ape and the Child.
Here’s footage of Gua and Donald together in happier times. You probably want to mute the bizarre techno music. Not sure what Dr. Kellogg was thinking with that.
By the way, I think we need more scientific experiments that include chimp tickling.