[8] Russon began to study orangutans because she felt that they had been neglected in previous research on great ape intelligence, despite growing evidence of their complexity.
[4] Also, captive orangutans are often mistreated, and therefore emotionally or mentally damaged, making them inadequate study subjects.
In 1993, Russon published an article with co-author Birute M Galdikas, titled Imitation in free-ranging rehabilitate orangutans (Pongo pygmaeus).
In this book, field and laboratory researchers show that the Great Apes are capable of thinking at symbolic levels, traditionally considered uniquely human.
[5] In 1998, Russon published an article with coauthor Richard W. Byrne titled Learning by Imitation: A hierarchical approach.