Abstract # 2665 Event # 26:

Scheduled for Saturday, September 19, 2009 11:00 AM-11:10 AM: Session 3 (Del Mar Room) Oral Presentation


NURTURE, NOT NATURE, DETERMINES COMPREHENSION OF DECLARATIVE COMMUNICATION IN CHIMPANZEES (PAN TROGLODYTES) AND BONOBOS (PAN PANISCUS)

H. Lyn1,2, J. L. Russell2 and W. D. Hopkins1,2
1Agnes Scott College, Department of Psychology, 141 E. College Ave, Decatur, GA 30030, USA, 2Yerkes National Primate Research Center
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Human children are highly motivated to share information with others. By 12-15 months of age, children begin spontaneously pointing imperatively to request objects, but also declaratively – simply to draw the attention of adults to specific objects. Although recent studies in great apes have demonstrated evidence of imperative pointing in apes, a series of papers have delineated the absence of declarative communication in chimpanzees and have suggested that the ability to comprehend declaratives is biologically based and may have driven the evolution of human language. We tested 3 groups of differently-reared chimpanzees and bonobos for their ability to use declarative signals in an object choice task. Significantly higher scores were obtained from two groups of apes that were reared in a socio-linguistically complex environment compared to a standard-reared group [F(2, 14)=9.13, p=0.003]. The results further showed that all three groups were more sensitive to combined gesture and vocal cues compared to either gesture or vocal cues when presented alone [F(2, 26)=4.03, p=0.03]. Our results are the first to demonstrate that environmental factors directly influence great apes’ ability to comprehend declarative signals. As experience in a socio-linguistically rich environment, not biology, is the driving force behind comprehension of purely informative communications in apes, we must look elsewhere for a candidate biological change that allowed for the evolution of human language and cognition.