Abstract # 2430 Poster # 109:

Scheduled for Friday, June 20, 2008 05:00 PM-07:00 PM: Session 12 (Ball Rooms A and B) Poster Presentation


MANUAL MOTOR SKILL IS ASSOCIATED WITH ORO-FACIAL CONTROL OF VOCAL SIGNALS IN CHIMPANZEES (Pan troglodytes): IMPLICATIONS FOR THEORIES ON THE ORIGINS OF SPEECH

J. L. Russell1 and W. D. Hopkins1,2
1Department of Psychobiology, Yerkes National Primate Research Center, 954 Gatewood Road, Atlanta, GA 30329, USA, 2Department of Psychology, Agnes Scott College, Decatur, Georgia 30030
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     Human language and speech as a form of communication is unparalleled in the animal kingdom. Many have argued that the neural mechanisms underlying the motor control of language and speech are fundamentally different than those used in the vocal communication systems of other animals. In the current study, 130 captive chimpanzees were categorized as consistently (n=69) or inconsistently (n=71) producing attention-getting sounds based on previous studies examining multimodal communication in these apes (Hostetter, Cantero, & Hopkins, 2001; Leavens, Hostetter, Wesley, & Hopkins, 2004). These two cohorts were compared on two fine motor tasks and four handedness measures. Results indicated chimpanzees that reliably produced attention-getting sounds made significantly fewer grasping errors on a simple reaching task [t-test, a=0.05] and performed better on a tool use task [t-test, a=0.05] than those that did not. In addition, chimpanzees that reliably produced attention-getting sounds were significantly more right-handed for all four handedness tasks than those that did not [ANOVA, a=0.05]. None of the effects were modulated by sex or rearing variables. These results suggest that the motor control of manual actions and oro-facial movements are lateralized to the left hemisphere in chimpanzees. Lateralized volitional control of oro-facial movements and distal musculature may have served as the foundation for the subsequent evolution of language and speech in Hominids.