On this page you will find information about the research that I’ve carried out with the signing chimpanzees.

In the 1990s, working from the University of Nijmegen in The Netherlands,  I carried out an investigation into the nature of the signing behaviour by the famous signing chimpanzees at the Chimpanzee and Human Communication Institute (CHCI) of Central Washington University in Ellensburg, Washington State (USA). I analyzed 22 hours of videotapes of the use of signs by the famous chimpanzees Washoe, Moja, Tatu, Dar and Loulis when they were in interaction with longtime human companions, filmed in the period 1992-1999. The total corpus of chimpanzee sign use that I gathered contained 3,448 utterances that could be used for analysis.

The results of my research were as follows. The chimpanzees predominantly used object and action signs. There was no evidence for semantic or syntactic structure in combinations of signs. Longer combinations showed repetition and stringing of object and action signs. The chimpanzees mostly signed with an acquisitive motivation. Requests for objects and actions were the predominant communicative intention of the sign utterances, though naming and answering also occurred. My conclusion on this recent sign use by the chimpanzees is that it shows multiple differences with human language.

In 2003 I got my doctoral degree from the University of Nijmegen by defending my dissertation GIMME GIMME GIMME. The recent signing behaviour of chimpanzees (Pan troglodytes) in interactions with longtime human companions. My dissertation describes the history of sign language research with chimpanzees and presents in full detail my own research with the signing chimpanzees.

Click here for a pdf file of my dissertation.

In 2005 I was able to publish my first scientific article about my study on the recent use of signs by the famous signing chimpanzees in the Journal of Comparative Psychology. Click here for a pdf file of the article.


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