When Your Sibling Is a Chimp

Imagine having a chimp as your sibling? How would that be? Well, that's the story of Donald Kellogg, son of psychologist Winthrop Kellogg. In simple terms, the investigation aimed to test whether a chimpanzee can acquire human behaviors if it is transferred to a human environment. To do this, Kellogg raised Gua, a young female chimpanzee, along with his son Donald, who was ten months old at that time.

According to Benjamin and Bruce (1982), Kellogg was probably inspired to conduct such a strange experiment after reading an article about the 'wolf children' of India published in the American Journal of Psychology (Squires, 1927). The wolf children were two girls who were reported to be discovered in a cave, living with a wolf's pack. The article states that the two kids behaved like wolves and could not acquire proper human behaviors even after bringing them back to a civilized environment. In the article, Squires argued that the feral children had a subnormal level of intelligence, and hence, they were not capable of adapting to their new environment.

But Kellogg was not satisfied with this explanation. In his later articles in the American Journal of Psychology, Kellogg suggested that it was most likely that the feral children were born with normal intelligence. If that was not the case, they wouldn't have survived in the wild in the first place. Kellogg's opinion was that the existence of critical periods in development and the significant impact of early experiences were responsible for the feral children's problems after returning to the human environment.

The critical period is a window of time immediately after birth, during which experiences and the environment strongly influence the development of the brain's various functions. The critical period concept opens an arena for the heredity versus environment debate- to what extent are our traits genetically determined, and to what extent are they influenced by experiences? The total absence of certain crucial experiences during the critical period can negatively affect the development of the associated brain functions.

To test his hypothesis, he designed an experiment in which a young ape is raised in a human home along with a human child that is almost as old as the ape. Kellogg was insistent that the animal used had to be very young and also that the experimenters should always treat it as a human and not as a pet. Gua was acquired from Yale's Anthropoid Experiment Station, Florida, to put this plan into action. For the next nine months, Donald and Gua were raised together in identical rearing conditions. Kellogg devised numerous tests to compare the development of the two infants. During those nine months, Donald and Gua were tested daily to compare blood pressure, memory, body size, scribbling, reflexes, language comprehension, attention span, among other things.

Although Gua was able to produce many meaningful sounds, the ape never succeeded in mastering words. She didn't even go through a period of babbling that is observed in human infants. Gua never imitated Donald's vocalizations, but at 14 months, Donald started mimicking Gua's food barks. Also, at 11.5 months, Donald's vocabulary consisted of 3 words. At 19 months, his vocabulary was still limited to just three words. Actually, Donald had learned six words, but Kellogg observed that for every new word the child learned, one word

Figure 1.Gua and Donald

Figure 2.Gua and Donald and Winthrop