Raising an infant chimpanzee the human way is not an easy thing to do.
Aside from Gua's fondness for insects, flowers, and whatever else she could stick in her mouth, she was also much more active than her "brother" Donald. Being constantly thirsty, she became a frequent user of water faucets after learning how a water tap worked. She also enjoyed baths, except for her tendency to eat the soap, and enjoyed sleeping in a regular bed. Once, when the bed was removed for cleaning, Gua cried until it was returned. As for how they behaved while sleeping, the Kelloggs reported that both Donald and Gua looked and acted much the same when sleeping at night including having the same posture and acting the same way on awakening.
But there were still important differences between Donald and Gua. When it came to picking up a piece of food, for example, Gua often used her mouth since she was incapable of grasping with her hand the way Donald could. Even when the Kelloggs tried to teach her to grasp objects with her hands, she was often clumsy due to lacking an opposable thumb. Gua also had trouble with building blocks since she didn't hae the motor precision of a human child.
In terms of learning to walk, there were other important differences. Donald took to using his walker to get around and was often "reckless" in trying to walk without it. As for Gua, she never learned to use the walker though she enjoyed being pushed around by someone else. She continued to use the walker as a toy even after learning to walk but there were still marked differences in the walking styles they adopted, however.
By the age of eight months, Gua was responding to her reflection in a mirror and she also noticed changes in her environment much faster than Donald did. At the age of fourteen and a half months, both Donald and Gua were shown a child's alphabet book. Though Gua was faster at attending to visual content, Donald learned to point to a picture that an adult had just indicated. Gua, on the other hand, tried to lift pictures from the page suggesting well-developed depth perception.
Gua's hearing was also much more acute that Donald's (or his human parents) and she often responded to sounds like the newspaper being delivered much sooner than anyone else. When it came to localizing sounds, Donald and Gua showed no real difference that the Kelloggs could determine. Another problem was that Donald could signal that he disliked something he tasted by his facial expressions, something they were never able to achieve with Gua. Not only was Gua's sense of smell much more acute than Donald's, but she also depended on smell to identify people much more than Donald did. Whenever meeting someone for the first time, Gua would smell them first and rely on her sense of smell to recognize everybody she met.
Gua had a number of overwhelming fears during her time with the Kelloggs. She was terrified of being left alone and was often anxious whenever her human parents exited the house. She was also terrified by far-off noises such as planes passing overhead. Other fears came from learned experiences. After a small dog snapped at her when she cornered it, Gua became afraid of small animals. She was also terrified of toadstools after being unintentionally poisoned by one when she ate it. There were also frequent tantrums, especially when Donald received treatment she didn't get.
But she was good at learning to be as human as possible. It took a while but the Kelloggs got her used to being dressed in human clothes and to allowing her nails and teeth to be cleaned. She also picked up toilet training, how to use a light switch, how to eat with a spoon, and how to drink from a glass. Donald and Gua were regularly tested using standard test batteries intended for infants. Though Gua was more advanced than Donald at first, he quickly overtook her. Since the tests were never designed for infant chimpanzees, it is hard to make any firm conclusions about problem-solving or memory. Still, Gua's cognitive development was steadily increasing as a result of her enriched upbringing.
It was trying to teach Gua to speak that generated the most interest from outside observers. Up until that time, the prevailing scientific consensus was that only humans were capable of true speech (as opposed to mimicry seen in parrots and other birds). Since the 19th century, brain researchers had known that the human capacity for language was linked to specific regions of the brain that were largely absent in chimpanzees and other non-human primates. Given their belief in behaviourist theories of language development, the Kelloggs reasoned that Gua could be taught language skills in much the same way that human children were. And this is where the experiment went sour.
Through the course of the Kellogg study, Gua learned to use facial expressions and developed her own hand gestures to express what she wanted. As Winthrop Kellogg later wrote, "Almost from the beginning of her human training, Gua seemed to possess a rudimentary, nonvocal form of communication by means of which her impending actions could be predicted by those who knew her well. " While Robert Yerkes had actually proposed teaching chimpanzees sign language, the Kelloggs focused on actual spoken language in their experiment.
What they found was that Gua was capable of a wide range of articulations and grunts. However, teaching her even simple words like "pa-pa" seemed just about impossible despite repeated efforts. Though not dismissing the possibility of chimpanzee speech completely, they concluded that Gua would never be capable of speaking more than a handful of words. As for whether Gua was successful in learning to understand human language, this is something the Kelloggs simply failed to follow up on.
This was deeply disappointing to the Kelloggs and may have coloured their impression of the other things that Gua had been successfully taught to do. But it when they saw the effect that all of this was having on Donald that things became, ahem, somewhat hairy.
To be continued.