She has been studying intelligence and learning in orangutans since 1989, in Indonesian Borneo. Her research was affiliated with the Orangutan Research and Conservation Project until 1993 and the Anariset Orangutan Reintroduction Project since 1994. She has published numerous research and popular articles on orangutan intelligence, given academic and public presentations, and co-edited a book on great ape intelligence, Reaching into Thought: The Minds of the Great Apes. Her most recent book is Orangutans: Wizards of the Rain Forest.