Abstract
A number of studies from the 1960s to 1990s assessed the symbolic competence of great apes and other animals. These studies provided varying forms of evidence that some species were capable of symbolically representing their worlds, both through productive symbol use and comprehension of symbolic stimuli. One such project at the Language Research Center involved training chimpanzees (Pan troglodytes) to use lexigram symbols (geometric visual stimuli that represented objects, actions, locations, and individuals). Those studies now are more than 40 years old, and only a few of the apes involved in those studies are still alive. Three of these chimpanzees (and a fourth, control chimpanzee) were assessed across a 10-year period from 1999 to 2008 for their continued knowledge of lexigram symbols and, in the case of one chimpanzee, the continued ability to comprehend human speech. This article describes that longitudinal assessment and outlines the degree to which symbol competence was retained by these chimpanzees across that decade-long period. All chimpanzees showed retention of lexigram vocabularies, although there were differences in the number of words that were retained across the individuals. One chimpanzee also showed continual retention of human speech perception. These retained vocabularies largely consisted of food item names, but also names of inedible objects, locations, individuals, and some actions. Many of these retained words were for things that are not common in the daily lives of the chimpanzees and for things that are rarely requested by the chimpanzees. Thus, the early experiences of these chimpanzees in symbol-rich environments have produced long-lasting memories for symbol meaning, and those competencies have benefited research in a variety of topics in comparative cognition.
Highlights
Ape language research has its early roots in cross-fostering studies conducted in the early twentieth century [1,2]
Lana averaged 30.7 words known per year, and she had 17 words that were known for at least 8 of 10 years, a savings measure of 55%
Lana clearly had the smallest vocabulary throughout this time range, and she had the lowest savings measure of the three chimpanzees
Summary
Ape language research has its early roots in cross-fostering studies conducted in the early twentieth century [1,2]. Testing was conducted around the time that these chimpanzees were approximately four years old and while their ASL acquisition and usage was still developing During the time these sign language studies were being conducted, a different kind of study emerged looking at the ability of a chimpanzee named Lana to learn and use a symbol system of geometric patterns called lexigrams. Panzee was co-reared with a female bonobo (Pan paniscus) named Panbanisha, and this project employed a different learning regimen These two chimpanzees were raised from birth in a manner similar to humans, hearing and responding to speech from the age of eight days old [30,31]. The continued symbolic competence of these chimpanzees affords unique experimental opportunities, and those opportunities rely on the present data to outline and define what symbols might be used in other cognitive task contexts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
